LEARNING FROM THE BIGGEST LOSER
The singer Tennessee Ernie Ford was correct: It is important to know your audience, but it also important that you know your author so that you understand my approach to this topic I am a college professor and research scientist For the past 40-plus years I have been teaching psychology and biology undergraduates, first-year medical students, neurology residents, and psychiatrists about the workings of the brain I am a neurochemist and pharmacologist by training My laboratory research focused on how food and drugs influence how we think and feel and how well we age Thus, my emphasisinthisbookisonthebrainandhowitshealthandfunctionareinfluencedbyexercise
My young undergraduate students are endlessly fascinated by how their brain works You might predict that this fascination is motivated by their natural curiosity and desire to advance their education You would be wrong The most common question that I am asked during my office hours is “Hey, Doc, I ate (or drank) this last night What do you think it might do to me?” while holding out an emptyvialorpackage
After hearing this question from my 19-year-olds for so many years, I have come to the conclusion thatthereisonlyoneexplanationfortheirbehavior:Theyfeelimmortal Theybelievethatbecausethey are young, they are immune to the dangers of life As a brain scientist, I blame these feelings of immortality on the fact that their frontal lobes are not fully working because their brains have not yet completed the maturation process Neuroscientists discovered many years ago thatthe parts ofhuman brainthatevolvedmostrecently,andthusgiverisetothesophisticatedmentalabilitiesthatweusually associatewithadultbehavior,arethepartsthatmaturelast Ifyouareaparent,thatlaststatementdid not surprise you The frontal lobes, the part of the brain that contributes most to our unique personalities and allows us to anticipate the consequences of our imprudent actions, matures last Essentially, the frontal lobes of my students should tell them that it’s a bad idea to drink alcohol and drive,ortoignoretheconsequencesontheirhealthofeatingcheeseburgersandpizzaeveryday,orthe costs of binge drinking every Thursday evening Usually, when their frontal lobes finally complete the maturation process, they stop doing stupid things Most importantly, they should stop acting as though they are immortal Females do not have fully mature brains until they are about 25 years old; unfortunately, the males must wait until they are about 30 years old to enjoy the benefits of a fully maturedbrain EverysemesterIliketoremindmy19-year-oldfemalestudentsthatdatingaguywhois also 19 years old is roughly equivalent to dating a boy with a 16-year-old brain At this point, the females in the classroom are typically nodding their heads in recognition that what I just said is painfullyfamiliar
Year after year, my 19-year-olds offer testimonials in class, in front of about 200 of their peers (they neverhesitatetoovershareinagameofpharmaceuticalone-upmanship),detailingtheevidenceoftheir immaturebrainstructure Oneyoungfemalestudenttoldthisstoryinclassonemorning:Shesaidthat she had met a woman in a bar the previous night who claimed to be a “nurse” (an immature brain also makes one rather gullible) who offered to give her some pills She admitted that she had no idea what these pills contained but was promised by her new friend that it would be a fun experience She accompanied the “nurse” to her apartment that was nearby Her experience included hallucinations, heartpalpitations,andafever,consistentwithhavingconsumedthepopularstreetdrugEcstasy WhatI found astonishing was that this young woman did not seem at all disturbed by the fact that she had willingly allowed a total stranger to place her health at risk She told the class that when she woke in the morning she gotdressed (she did notremembergetting undressed)and came to class Forreasons thatIwillneverunderstandfully,shewaseagertoshareheradventureswiththeentireclass
The male brain completes its final stages of maturation much later than female brains Thus, my 19year-oldmalestudentstendtomakedecisionsthatareequallyreckless,butforamuchlongerperiodof time One of my male students described the following experience in class During the previous weekend he became bored and decided that it might be fun to ingest a packet of instant coffee, right out of the box He popped an entire packet (paper included) into his mouth and swallowed it Apparently, he enjoyed the rush so much that he decided to finish off the entire box of 32 packets! Threedayslater,hestoppedhavingexplosivediarrheaandfinallyfellasleep,completelyexhausted You can now fully appreciate why car insurance rates go down for women at age 25 years and for men at age30years;ithaseverythingtodowiththematurationofthefrontallobes
I once thought that the widespread access to all knowledge on the internet would allow my students to inform themselves of the risks of certain behaviors before they could get themselves into serious trouble Sadly, this has never been the case; the internet tends to give them a false sense of security Forexample,oneyoungmanannouncedtotheclassthathehaddiscoveredanopiumpoppygrowingon hispropertyduringthepastweekend Hecheckedontheinternettoconfirmtheidentityoftheplant I asked him what he did with it I assumed that after checking the internet he would discover that he should handle this plant very carefully and certainly not eat it I was wrong; he proudly announced to
theclassthatheateit
“Theentireplant!?”Isaid “Yes,ofcourse,”hesaid
I then asked the most obvious question that was certainly on the minds of everyone else in the room thatday:“Whathappened?”
He said, “A couple hours later my girlfriend found me unconscious in the yard and called 911 It was anamazingexperience”
Notforaseconddidhebelievethathislifewasatriskbyhisrecklessbehavior Hefeltimmortal
Decades of unbelievable stories by these immortal young men and women led me to write a book called Your Brain on Food (Oxford University Press) that I use as the textbook for my Introduction to Psychopharmacology course The main point of the book is that anything that you consume can affect your brain function, how you think, how you feel, and will influence how fast your brain ages I discovered that my students displayed caution when using over-the-counter or prescription drugs but often demonstrated a cavalier, and occasionally irresponsible, indifference to the effects of what they ateordrank Afterall,ifit’s“food”itmustbesafe Iwrotethebooktohelpthemunderstandwhythey should be cautious about anything that they consume, whether it is a food or drug or something in between,suchaschocolateorcoffee
Obsessionswithselecteddrugsarenottheonlytopicstheydiscussduringclassorofficehours Many ofmystudentsarealsoobsessedwithsomeformofexercise,suchasteamorindividualsportsoroneof themanypopularextremesportssuchas72-hourjogging,paraskiing,orvolcanosurfing(it’sactuallya lotoffun,althoughitripsyourclothestoshreds) Eachyear,manyofmystudentstalkabouttheirdaily yearning to run or swim; these are the obligatory athletes They are driven to run 10 to 20 miles or swim four hours every day, no matter how inconvenient to their daily schedule or how much physical pain it produces This addiction occurs primarily with aerobic exercises rather than anaerobic ones I will discuss why this is so in a later chapter Frequently, my obligatory athletes come to class and promptlyfallasleepfromexhaustion Needlesstosay,theirclassroom performancesuffersduetotheir exerciseaddiction Theyareasaddictedtoextremeexercisingasadrugaddictistoheroin LaterIwill explainhowidenticalbrainregionsareresponsibleforbothaddictions
Many of my obligatory athletes defend their addiction by claiming that daily exercise is the only way they can lose weight and remain healthy Heroin addicts usually have explanations that also sound rational Is an exercise addiction really as harmful to your health as a drug addiction? In many ways, yes, if it is taken to excessive levels One of the main problems with an exercise addiction is that it requires that the obligatory athlete consume 3,000 to 4,000 calories every day My obligatory athletes areconstantlyeatingorthinkingabouteating
Consuming so many calories every day has a negative effect on overall health Why? Due to the increasedrequirementforadditionaloxygentometabolizeallofthatfood,high-caloriedietsaccelerate the aging process The relationship is linear: The more you eat, the faster you age and the sooner you die Ironically, their initial desire to become healthier by jogging to lose weight addicted them to the extreme exercising routine thatrequired them to consume thousands ofextra calories thataccelerated their aging The biochemical processes inside all living multicellular creatures that link eating with movement and tissue aging were forged billions of years ago and cannot be circumvented You are probablywellawarethatwhatyoueateverydayinfluencesyourhealthintheshortterm;however,how much you eat every day also influences your health over the long term and determines how fast your bodyages AlthoughIdiscussthistopicinclasseveryyear,thelessonneverseemstostick
Unfortunately, my students’ obsessions also include adherence to one of the many popular diets that are either unhealthy or have absolutely no scientific basis, such as the paleo diet, the Atkins diet, “The Zone,”theDukandiet,theapplecidervinegardiet,thecoconutoildiet,thelow-carb/high-proteindiet, the high-carb/low-fat diet, the cotton ball diet, or the misleadingly named and most scientifically goofy ketogenic diet These diets frequently produce harmful effects on the kidneys, heart, and liver that undermine any potential health benefits that might be obtained from exercising I do not understand why my students expend so much effort to exercise and then undermine their efforts by following the foolishadviceassociatedwiththesefaddiets
One of the most popular fad diets lately is going gluten-free Many of my students have decided to become gluten-free for absolutely no medical reason Is eating gluten always bad for everyone? Absolutely not If you are not gluten-sensitive, then avoiding gluten is a bad idea according to the resultsofalargeresearchstudyinvolvingover15,000participantswhowerefollowedfor30years The American College of Cardiology now strongly recommends against the adoption of gluten-free diets for peoplewithoutamedicalnecessity Thus,unlessyousufferwithceliacdisease,goinggluten-freeisnot a good dietary decision Gluten-free diets, like so many other fad diets of the past and present, have been promoted by uninformed or willfully ignorant nutritional prophets (too often by phycians, who shouldknowbetter)usingdietaryscaretacticstoscamafewdollarsfromamisinformedpublic
The interesting thing about diets and exercising is that we are always being instructed to get the right amount of both What precisely does this mean? Usually, the goal is to avoid becoming obese so that we can live a long, healthy, and active life Why is being obese so unhealthy? The culprit is the same one that explains why it is so unhealthy to consume 4,000 calories every day: oxygen, and your requirementforaconstantsupplyofitinordertometabolizeyourfood
Thanks to the impact of social media, the fashion industry, government health agencies, and high school health classes, everyone is aware that carrying around too many extra pounds of fat is unwise
Obesity reproduces, and also accelerates, many of the same metabolic conditions that underlie the normal aging process Decades of research have demonstrated that obesity increases the risk of diabetes, atherosclerosis, and especially cancer and, with regard to its effects on the brain, increases the likelihood of becoming depressed and then makes it harder for antidepressant therapies to work For the past few decades I have witnessed first-hand the negative consequences of obesity on the qualityofthelivesofmanyofmystudents Myobesestudentsareoftenshunnedbyothersandperform more poorly in class than students who are thinner Notice that the relationship is between amount of body fat and academic performance, not between exercise and academic performance As will become clear later, exercise does not significantly enhance cognitive performance; however, body fat does significantlyimpaircognitiveperformance
Is there a biological relationship between being obese and not doing well in school? Yes, there is Doesexcessbodyfatmakeyoustupid?Yes,itdoes Numerousepidemiologicalandclinicalstudieshave clearly demonstrated that obesity is a definitive risk factor for cognitive deficits and impaired memory in young and old humans One recent epidemiological study concluded that by the year 2050 the percentage of overweight or obese Americans will increase to over 50% This statistic is alarming because of the severe consequences on the body and brain of being obese Obesity also increases the incidence of numerous diseases that will place great demands on the nation’s medical bill, particularly MedicaidandMedicare,asthegeneralpopulationgetsolder Why?
Fat is toxic to your body and brain Many laboratories around the world, including my own, have documented the mechanisms that underlie how excessive body fat impairs brain function Scientists have focused on the obesity-induced degenerative changes that occur within a brain structure called the hippocampus The normal function of the hippocampus is critical for the formation of new memories Thisbrainstructure will be the focus of many later discussions about the effects of exercise on the brain Recent studies have reported specific abnormalities in the general health of cells within thehippocampusthatunderliethememoryimpairmentsrelatedtoobesity
Allofmystudentsweretoldinelementaryschoolthattheyshouldeatrightandexercisesothatthey performattheirpersonalbestinschooloratwork Whatistheoptimalbalanceoffoodandexercisein order to obtain a healthy body? My impression is that my students were not given enough information tomakethisjudgementforthemselves,becauseyearafteryearIgetthisquestion:HowmuchshouldI exercise every day to become healthier? Unfortunately, that is the wrong question The answer has nothingtodowithexercising;rather,Itellthemthathowlittletheyeateverydayisfarmoreimportant thanhowmuchtheyexerciseeveryday
I am not the only person who preaches this sermon The trainer for the popular NBC television show “TheBiggestLoser”usedtothinkthatmoreexercisewasallthatwasnecessaryinordertoloseweight and get healthy After many years of helping severely obese people lose weight, however, Bob Harper concluded that exercise is not the key; diet is far more important than exercise Not only is Harper helpinghisclientstofeelbetterandachievetheirpersonalgoals,heisalsohelpingthemtolivelonger, healthier lives His clients are now instructed to consume fewer calories every day in order to reduce theirlevelofexcessbodyfat
Fat accelerates aging and increases your risk of dying How? Fat cells produce inflammation Lots of it What is the best way to reduce inflammation in your body? In order to answer this question, scientists investigated whether diet or exercise more effectively reduced the levels of inflammation in overweightorobesewomen After12monthsofinvestigationthescientistsconcludedthatthegreatest weight loss and most significant reduction in the level of inflammatory protein reduction came only from dieting The women who participated in an exercise-only program showed no reduction in inflammatory proteins The reasons for this lack of change in the level of inflammation following exercise will become apparent in later chapters Essentially, unless you are a marathon runner, a triathlete, or an Olympic-level swimmer, the activity of your musculature is not a big player in calorie consumptionorbodyfatreduction
Although the results of these studies on humans are interesting, sometimes it is possible to get more detailed data from studies of nonhuman primates Fortunately, nonhuman primates share critical features of our physiology In order to investigate the benefits of caloric restriction, a large group of monkeys, ranging from middle-aged to quite elderly, were fed only 70% of their free-feeding diet for about15years Forsomeoneeatinga2,000-calorie-per-daydiet,thiswouldbeabout600fewercalories per day As a result of eating just 30% fewer calories, the brains of the monkeys on the restricted diet agedsignificantlymoreslowly,andthemonkeysdevelopedfarfewerage-relateddiseases,hadvirtually no indication of diabetes and almost no age-related muscle atrophy, and lived much longer Most importantly, and consistent with Bob Harper’s conclusion, these monkeys did not exercise the weight off; they simply consumed fewer calories every day This was a rather shocking discovery: What is the valueofexercising,ifnottoloseweight?Aswillbecomeclearinthefollowingchapters,moderatedaily exercising does offer real health benefits for your body But that’s not the question being asked in this book:Doesyourbrainbenefitaswell?
I discovered that the answer is more complicated and more interesting than I had expected Some of our assumptions about the benefits of exercise are simply not true Although a little exercise is good, too much can produce harm Furthermore, the type of exercising directly influences the benefits we obtain Inmanyways,theeffectsofexerciseonthebodyparallelthoseoftheeffectsoffoodanddrugs that I described in my book Your Brain on Food The puzzling discoveries I made while reviewing the availablescientificliteratureledmetoaconclusionthatbecamethetitleofthenextchapter
THE DEVIL IS IN THE DETAILS
Movement has always been a required part of survival; thus, evolution has finetuned the enzymatic machinerythatgeneratestheenergyrequiredforphysicalactivity Theenvironmentalforcesthatdrove these evolutionary processes never anticipated that in the late 20th century a species would develop a culture that effectively disconnected the ancient link between physical activity and survival You can remain physically inactive and still survive in our culture You can earn a living while sitting in your pajamasatyourcomputer Fullyprepared,healthymealscannowbedeliveredtoyourdoor;noneedto gooutforagingandriskinjuryordeath Consequently,today,physicalinactivityhasemergedasamajor risk factor for your brain health and survival One of the best and most comprehensive studies investigating the relationship between physical fitness and mortality found that both men and women lived significantly longer by exercising regularly Avoiding a sedentary lifestyle delays death primarily duetolowerratesofcardiovasculardiseaseandcancer
Nevertheless,shouldbeingtoosedentarybeconsideredequivalenttosmoking,assomeauthorshave claimed? Not really Smoking is considerably worse than being sedentary; however, if given the choice, you should do neither Indeed, as will become clear later, obesity, not inactivity, should be considered equivalent to smoking Obesity impairs cognition and increases the risk for some psychiatric disorders and dementias and is responsible for far more hospitalizations and deaths every year in the United States than tobacco smoking Worse, obesity is an intergenerational problem; if the mother and father areobese,theysignificantlypredisposetheiroffspringtopoorcognitiveabilities
Butare we allreally thatinactive? In spite of warnings on the internetthatare primarily intended to motivateustobuyanothertreadmilloracolorfulpairofyogapants,mostofusprobablyachievealow level of modest exercise every day that benefits our overall health If we are to believe the data from people using devices that measure their daily number of steps, a healthy person usually takes about 6,000 to 7,000 steps per day just completing their normal daily tasks A 30-minute stroll after dinner could add another 3,000 steps if anyone bothered to do so Overall, such a routine could provide the essential level of exercise that today’s health experts recommend for good cardiovascular health However,isthismuchexerciseperweeksufficienttokeepyourbrainhealthyandallowittoperformits two most basic functions? The answer is a highly qualified yes, especially if you restrict your calorie intake,butmoredetailedresearchneedstobeperformedinordertobecertain
Brains evolved to perform two basic functions that usually involve muscle activity: your personal survival and the procreation of your species This is true for all known animals, even those with the most simplistic nervous systems Your brain utilizes information gathered by your sensory systems, considersitsoptions,andtheninstructsyourmusclestocontractinordertoobtainfood,findreceptive mates for reproduction, or avoid predators Thus, your brain achieves its primary goals via control of yourmuscles However,beyondtheobviousbenefittosurvivalandprocreation,doesyourbrainbenefit fromthesimpleactofhavingyourmusclescontract?Isexercisebeneficialtothebraindirectly,oronly indirectlyviaitseffectsonthebody?
In order to answer these questions,I firstneed to define exercise Exercise is a subsetof allpossible physical movements For most of us who are not professional athletes, exercise is a planned, socially structured, and repeated behavior performed with the intent to maintain or improve some aspect of physical fitness Given this definition, it is unlikely that other animals participate in exercise for the same reasons offered by human athletes Exercise is a special form of movement that is not related to findingfoodorareceptivemate(ignoringthepredatorybehaviorsofmalesatfitnessclubs)
Alackofregularexercise,sedentarylifestylesthatdonotrequiremuchactivity,andhigh-caloriediets togethersynergisticallyimpairbodyandbrainhealth How?Theanswerissimple:Thesebehaviorslead to increased numbers of fat cells, and fat cells produce widespread oxidative stress and inflammation Inflammationisveryharmfulbecauseitpredisposesustodisease,injury,cancer,andearlydeath
The inflammation inferno
Inflammation refers to high concentrations of a group of proteins that originally evolved to protect us from invading organisms and poisons in the environment Today, due to our high-calorie diet and sedentary culture, humans have almost entirely flipped the function of these inflammatory proteins from one of protection to one of harm Thanks to our tendency to eat too much and move too little, the additional fat that we carry around inside our body leads to the release of ever-increasing levels of inflammatoryproteinsthathavetoxiceffects
How can you best protect yourself from these toxic inflammatory proteins? Numerous recent studies have concluded that diet is far more effective than exercise for reducing the levels of inflammatory proteins in obese humans Study after study has demonstrated that the greatest weight loss and the most significant reduction in the level of inflammatory proteins come from reducing your total caloric
intake These results are very important; I will return to the consequences of inflammation when I discusshowexerciseaffectsthebrain
For those people who think that they can eat whatever they wish and then simply exercise away the calories (I am talking primarily to young males here), the news is not good In some ways, our bodies negatively adapt to daily physical activity Our bodies work against our attempts to exercise off those extrapoundsviaprocessesthatevolvedmillionsofyearsagoandwereoriginallyintendedtoallowour bodiestomaintaintheirtotalenergyexpenditurewithinasafenarrowrangewhenfoodwasscarce The scarcityoffoodforourancestorsdrovemanyoftheadaptivephysiologicalchangesthatformthebasis of the principles outlined in the following chapters These adaptive mechanisms reduce the amount of energyusedformovementinordertoconserveitforotherbodyfunctions Thus,duetothisadaption,it ultimatelybecomesmoredifficulttoloseweightbyonlyexercising
It gets worse! Too much exercising for too long can suppress immune function and reduce reproductive success Essentially, for most of us, the activity of our musculature is never going to consumethebulkofourcalories Scientistsspeculatethatasweevolvedourbig,fast-thinking,energydemanding brain our ancestors lost the ability to metabolize a substantial number of calories via physicalactivity Ourbraintookpriorityoverourmuscles
Your intestinal factory
The nutrients from your last meal are currently being absorbed by your small intestines (mostly) and will soon become available to all of the cells of your body. The entire gastrointestinal system, including stomach, large and small intestines, and their related organs, such as the pancreas and liver, utilize nearly70%oftheenergyyoujustconsumedinordertomaketheremaining30%availabletotherestof your body. Your brain uses about 20% of the remaining available energy, and your other organs that allow you to reproduce and move around your environment (including your muscles and bones) utilize whatisleftover.Asyoucansee,verylittleenergyisleftoverforothertasksinthebody.
These percentages give you some idea of the priorities thinking about finding food and avoiding predators, finding and reproducing with other humans, and finally, the physical activity required to accomplish these goals that billions of years of evolution have set for your body to achieve. About 200,000yearsagothepredecessorsofourspeciestradedabigbrainandenhancedsurvivalabilitiesfor reduced reproductive success and fewer, smaller muscles. The devil is always in the details: This tradeoff underlies why humans do not give birth to litters and why it is so hard to exercise away those extra pounds. However, exercise does provide benefits, as long as it is performed in moderation. Your brainwillnottoleratebeingrobbedofitsenergyfortoolong;therewillbeconsequences.
All things in moderation
Overall, exercise can improve health; however, maximal benefits are achieved when moderate levels of physical activity are combined with reduced calorie intake. The principle of moderation not too much andnottoolittle appliestobothexercisingandeating.Why?Theanswerisrelatedtohowthecellsof yourbodyconvertthefoodyoueatintotheenergyrequiredtocontractyourmuscles.Thisprocessalso underlies why either eating or exercising too much is harmful to your body and brain. In order to understandwhy,weneedtotravelbackintime.
A LONG TIME AGO
Our search to discover the origin of the mechanisms that link the optimal functioning of your brain to theactivityofyourmusclesbeginsjustaftertheEarthformed,about46billionyearsago Thefirstlife forms appeared rather quickly,as soon as the Earth cooled to the pointthatwater remained in a liquid state That is why scientists at NASA are always excited to find planets or moons with liquid water on them Water, rocks, and heat are all that are necessary for life to arise The first “cells” that formed on the young Earth were very simple; they survived and thrived because they could produce their own energyandreplicate Theseprimitivecellsweresimilar,butnotyetidentical,towhatweknowtodayas bacteria The descendants of these simple single-celled organisms are still the dominant life forms on our planet The top five miles of the Earth’s crust, and possibly much deeper, is thick with them; they alsothrivethroughouttheentireatmosphere
About 32 billion years ago, thanks to the process of photosynthesis by cyanobacteria and blue-green algae, the oceans became saturated with oxygen; different forms of life took advantage of this highly reactive, and also very toxic, gas in order to enhance their ability to multiply and survive These primitive cells had the same goals as your brain does today: to survive in order to multiply The winner of this battle of life was, and forever will be, determined by whoever makes the most copies of themselves for the longest period of time Whatever life form failed in these goals quickly became extinct
Then,about2billionyearsago,someofthesesimplecellsbegantoorganizethemselvesintocomplex multicellular groups that evolved the ability to move around their environment Although our species appearedonthesceneonlyabout200,000yearsago,wesharethesamegoalasalloftheotherspecies thatprecededus:tosurviveinordertoprocreate Bothoftheseactivitiesrequiremovement
Oxygen: the devil’s Janus coin
Movement requires energy. The first simple cells that appeared were not very adept at making energy. They produced just enough for their own survival and replication; not much was left over for other purposes. One of these single-celled free-living organisms evolved a brilliant biochemical trick that allowedittoutilizetheabundantoxygenintheairfortheproductionoflotsandlotsofenergy.Oneday, itwasaSaturdayinlateApril,about1.8billionyearsago,thisoxygen-eatingsimplecell,todaycalleda mitochondrion, was engulfed by a somewhat larger single-celled organism and the two developed a wonderful symbiotic relationship where the smaller cell, now safely nestled inside the bigger cell, providedlotsofenergythatenhancedtheirjointsurvival.Thisadditionalenergycouldnowalsobeused foroneadditionalability movement.
The first appearance of simple muscle-like proteins that could change shape by utilizing this additional energy source probably occurred about 640 million years ago in simple sponges. These first muscles were involved in cell motility and survival by regulating the circulation of seawater to harvest nutrients. Muscles for movement have always been critical for obtaining food for survival. Thus, the biochemicallinksbetweenmusclefunctionandenergyutilizationevolvedconcurrently.Thefirstmuscle protein was a type of myosin. Myosin is a critical component of muscle fibers found throughout nature and in the muscles of humans The large muscles of your body were the result of a simple process of duplicationandmodificationofthesamegenesthatinitiallyevolvedintheseancientsponges
Survival, and the successful procreation, of bigger and more complex organisms was greatly enhanced by the ability to move toward sources of food and away from predators Thanks to the mitochondria, whose ancestors gave up their independent lifestyle, and their remarkable ability to utilize oxygen, considerable amounts of additional energy were now available for the development and activation of primitive muscle cells that could move the entire organism around its environment Selfpoweredmovementwasasignificantstepforwardintheevolutionofmorecomplexorganisms
Once again, the devil was in the details The abundant supply of energy came with one important condition: Every cell now required a constant, unending, and invariable supply of oxygen Fortunately, oxygen was abundant in the air Unfortunately, oxygen is incredibly toxic to cells I know that sounds crazy; everyone was taught in school that oxygen is critical for life It is, and thanks to hemoglobin in your red blood cells, the oxygen is transported safely to all of your tissues The role of hemoglobin in your blood is to bind oxygen tightly to itself in order to make a sufficient number of oxygen molecules availablefortheprocessofrespirationinsideeachofthethousandsofmitochondriainsideeveryoneof the 37 trillion (approximately) cells of your body (The 900 trillion bacteria, molds, and fungi that coexist inside your body also utilize the oxygen that you inhale) Hemoglobin’s other job is to keep the concentrationofoxygenlowenoughthatitdoesnotkilleveryoneofyourcellsintheprocess
This devil of a deal, with oxygen as the currency, resulted in at least three fascinating consequences First, it is the reason that there are only two sexes on this planet (I am ignoring the kingdom of fungi
and a recently discovered worm they discovered some interesting alternative solutions) Second, it explainswhymalesofallspeciesneverliveaslongasfemalesofallspecies(moreonthislater) Third, itexplainswhyallcomplexcells,includingyou,die Priortothisdevilishdealbetweentwosimplecells billions of years ago, sex and death did not exist For at least 2 billion years after life first appeared, cells just grew bigger and bigger until they divided into two “daughter” cells Unless an errant space rockfellonit,theseprimitivecellsneverdied Therewasalsonosexualreproduction;thesefirstsimple cells were neither male nor female Now, billions of years later, big, complex, multicellular, muscular humans age and ultimately die because of this ancient devilish deal with oxygen Today, we all require oxygen to metabolize our food in order to survive, procreate, and exercise Right now, while you are thinkingabouthowtoachievetheseimportantgoals,yourbrainisusingalotofoxygen Iknowthatit’s risky,butpleasedonotstopthinking
Active brains require a lot of energy As simple nervous systems evolved and became more complex, bodiesevolvedlongerandlongerintestinesinordertooptimizetheextractionofmoreenergyfromthe diet It is not surprising to discover that, for mammals at least, the length of the gut is significantly correlated with the total body mass Initially, this evolutionary modification was able to satisfy the increasingdemandsofbiggerbodies Brainsusealotofenergy;thus,youmightpredictthatbigbrains lead to the evolution of longer intestines However, a study of over 100 different mammals did not find any correlation between the size of the brain and the length of the gut Unexpectedly, there is a negative correlation between brain size and total body fat for most mammals but not for humans We humanshavebigbrains,biggerthanotherprimates,andwearefattertoo Why?Maybeourbighuman brains require lots of body fat in order to function optimally At first glance, this is a reasonable expectationgiventhatthebrainrequiresaconstantanduninterruptedsupplyofenergy Unfortunately, this explanation is not correct because, under normal circumstances (unless you have not eaten for a couple weeks!),the brain does notobtain its energy from fat Whatever pseudoscience explanation you might have read about related to the ketogenic diet is total nonsense Optimal brain function requires sugaraboveallelse Yourfeedingcentersare only capableofdetectingsugarinyourblood,notfatsor proteins That’s why it is not very satisfying to eat a meal that does not contain any simple carbohydrates Never forget, your brain will often prefer that you eat things that your body would preferyoudidnoteat:blamethatonevolution Manymoreexamplesofthisbrainfeaturewillappearin thefollowingchapters
Overall, humans have a big brain, a fatty body, and a gastrointestinal system that is fairly efficient at extracting energy for itself and its two principal customers, the reproductive system and the brain As you can easily appreciate, muscles were never a big part of the evolutionary equation However, humanshavelotsofmuscles;theyarecriticalforoursurvivalandprocreationandtheyneedtobefed
The quality of the diet, and the increased availability of nutrients, of our ancestors was also greatly enhanced by their newly discovered ability to control fire and cook their food This advance appears to have occurred sometime between 500,000 and 17 million years ago Exposing food to heat before consuming it allows our intestines to extract more nutrients from our diet, especially meat Meat is an energy-rich source of nutrients and minerals Around this same time a few significant genetic changes occurred in the expression of some gut enzymes that allowed our ancestors, and now us, to extract more energy from our cooked food in order to support movement, and ultimately exercise In the next chapter I will examine how we obtain energy from our food in order to support exercise because the processofobtainingenergyhasaconsequenceonbrainfunction
MAKING ENERGY FOR EXERCISE
In terms of weight, skeletal muscle is typically the most abundant organ of the human body Eighty percentoftheweightofeachmuscleiswater Althoughyourmusclesaremostlywater,theyconsumea lot of oxygen, overall about as much as your liver or brain Their basic function encompasses the maintenance of postural support, the generation of force and power during voluntary movements, and breathing Muscles also play a major role in keeping us warm; this is called thermoregulation Skeletal muscle is also responsible for a large portion of the oxidative metabolism Oxidative metabolism is a chemicalprocessbywhichtheoxygenyouinhaleisusedtomakeenergyfromthefoodyoueat;heatis produced as a byproductofthis metabolism You mighthave noticed thata few hours after eating your bodyfeelswarmer Peoplewhoconsumeacalorie-restricteddiettendtofeelcoldmostofthetime Your body heat is mostly generated by the chemical reactions taking place within your liver that is processing your food for absorption into all of your human cells as well as the many trillions of nonhuman cells that share your body Because free oxygen from the air is utilized in this process, it is called aerobic metabolism Aerobic respiration is a set of metabolic reactions and processes that take placeinyourcellstoconverttheenergystoredinsidefoodintoadenosinetriphosphate(ATP),andthen releasewasteproducts WhatmakesmakingATPsoimportantthateverycellinyourbodyspendsallof itstimeandenergyproducingit?
ATP
You should think of ATP molecules as the tiny batteries your body requires in order to stay alive. You mustconstantlymakethembecauseyouareconstantlyusingthemup.Theyarecritical.Whenyoustop making them you die. When someone takes cyanide in order to commit suicide, the reason they die is because the cyanide molecules prevent their cells, all of their cells, from making ATP. Death usually takes about 30 minutes (depending on dose and body size) and, due to the cellular mechanisms underlyingthedeathofeachcell,theprocessisextremelypainful.Forsomereason,wheneverspiesdie in an action movie by hurriedly crushing a cyanide pill in their mouth, it always appears to be fast and painless.It’sneither.
Muscles are also a major storage site for energy-rich nutrients, such as glucose, simple fats, and a large variety of amino acids; thus, your muscles play an essential role in coordinating whole-body energy production and metabolism. For example, amino acid metabolism in muscle rapidly adapts in response to physical exercise, the type of dietary protein available to the muscle, or the presence of hormones such as insulin-like growth factor-1 (IGF-1) or testosterone. IGF-1 is primarily produced by the liver. IGF-1, as its name suggests, is very similar to insulin and its release from the liver is induced by milk as well as other dairy products in the diet. This reaction to dairy may be related to our need, since humans are mammals, for milk during the first few years of life. Why humans continue to drink the milk of other (!) mammals into adulthood is likely related to culture rather than a biological need. No other mammal drinks the milk of another mammal only humans do this (and the occasional Jedi MasterlivinginexileontheaquaticplanetofAhch-To).
Getting back to IGF-1. IGF-1 can cross the blood–brain barrier and might act as a mediator of the exercise-induced changes in the brain (I will return to this important ability later) IGF-1 controls the release of another important hormone called growth hormone Together, testosterone and growth hormone control muscle development and growth, particularly during childhood It was once thought that muscle growth after weightlifting exercise was due to the combined actions of growth hormone and testosterone; however, recent studies have raised significant doubts about their combined impact onmusclegrowthafterliftingweights
A brief PSA
Please allow me to state the obvious at this point, given our general ignorance about the actions, and interactions,ofyourbody’shormones:Itisneverwisetotakesupplementsofthesehormones.Inducing an imbalance either too much or too little of them can produce devastating long-term harm to your body. This advice also applies to any attempts to compensate for age-related losses of specific hormones. Don’t do it! The balance of hormones and their interactions with each other are simply too complex to risk the consequences of consuming megadoses of any particular hormone supplement. Purveyors of supplements on the internet have no interest in your good health; they are far more interestedinincreasingthesizeoftheirpursethanthesizeofyourmuscles.
The importance of ATP
Yourbodyconsistsofaround600musclesthatmaycontributeabout40% ofyourtotalbodyweight As our understanding of muscle physiology advances it is becoming clear that muscles behave as though they are a complex endocrine system, much like your thyroid gland or pancreas Muscles send out chemical signals so that the brain and body are aware of what they are doing and their current metabolic needs However, unlike all of your other endocrine organs, your muscles can contract and dramatically change shape Surprisingly, although the contraction process of muscles has been studied for many years, the molecular details of the contraction process are still not fully understood What is wellknownisthatmusclesrequiretheenergystoredinmoleculesofATPforcontraction
ATP plays a critical role in every part of your body and is necessary for you to exercise It is an ancient molecule that existed naturally on the planet long before any life appeared The first primitive cells simply exploited whatever suitable molecules were lying around and incorporated them into their ownchemistry TheconstantdemandforsomanymoleculesofATP,andyourbody’sproductionofthem, primarilyviathemetabolicactivityinsideyourmitochondria,hasconsequencesonyourbrainfunction, yourgeneralhealth,andhowwellyouage Especiallyifyouareamale(moreonthislater)
Mitochondria make ATP
Mitochondria are small, membrane-bound organelles that, as I described earlier, were once free-living simple cells that now reside inside virtually every cell of your body. The mitochondria are essential for the production of ATP that your cells use for many critical chemical processes, including muscle contraction; however, the constant moment-by-moment demand for ATP has consequences on the qualityoflifeandultimatedeathofhumans.
Beginning about 3 billion years ago, the forces of evolution linked three vital processes together movement, energy production, and death and the nature of life on this planet changed forever. The biochemicalpowerplantthatachievesthislinkageisthemitochondria.Yourmusclescontainthousands of mitochondria. In fact, muscles contain more mitochondria per weight than any of your other tissues. Mitochondria have their own DNA and multiply independently of the cell in which they reside. They behave as though they still believe that they are the free-living, independent organisms that they once were so very long ago. Over time, our cells modified how the mitochondria function so that their primary function now is the generation of large quantities of energy in the form of ATP. They are the powercellsofyourcells.
Mitochondria use the carbohydrates, fats, and proteins from your diet to generate ATP. Glucose is a carbohydrate and is the simplest form of sugar. The adult brain has a very high energy demand requiring the continuous delivery of glucose from blood. The brain accounts for approximately 2% of the body weight but consumes approximately 20% of glucose-derived energy, making it your body’s foremost consumer of glucose. The largest proportion of energy in the brain is utilized for neuronal computationandinformationprocessing thatis,thinking.
Obviously,yourbrainrequiresalotofsugar;withoutaconstantuninterruptedsupplyyouwillquickly lose the ability to think and slip into a coma. You obtain most of this sugar from your diet. Sadly, somewhere in our evolutionary history, we lost the ability to convert fat into sugar; unlike a few lucky creatures,humanscannotperformthismetabolictrick.Humanscanmakeglucosefrommuscleprotein, but we need to break down the muscles, and this process requires lots of ATP. From your brain’s perspective,dietarysugarisindispensable.Itwilldowhateverisnecessarytoconvinceyoutoeatsugar as often as possible. I like to remind my students that sometimes your brain will demand that you consume certain foods and drugs that are not always good for the rest of your body. Sugar is an excellent example of this irony. The brain loves sugar and will reward you with feelings of euphoria for eatinglotsandlotsofsugar.Unfortunately,eatinglotsofsugareverydaywillultimatelyleadtoobesity and diabetes and predispose you to developing cancer. Needless to say, your brain also really loves fat and salt As everyone is well aware, the brain always wins this contest for control of what gets eaten Why? Because fat, salt, and sugar occurred very rarely in the environment during the evolution of brains Bodies require fat, salt, and sugar; thus, our brains evolved neurological mechanisms that rewarduswheneverweconsumethem Thus,today,weareallstuckwithafat-,salt-,andsugar-loving brain Unfortunately, the blind processes of evolution cannot work backward to correct what has becomeamajorriskfactorforlong-termhealth
So, in summary, you eat and breathe and your mitochondria provide energy for your muscles by metabolizing the carbohydrates, fats, and proteins that you consume The chemical machinery inside the mitochondria then gobbles as much energy from the process as possible for the production of ATP The fact that your mitochondria accomplish this task so inefficiently means that much of the energy in your food is lost as heat The heat generated by the thousands of mitochondria within muscles mostly explainswhyheavilymuscledmalebodybuilders,withtheirtissuesrichintestosterone,liketowearso littleclothingoncoldwinterdayswhentherestofusareshivering Ithasabsolutelynothingtodowith theiregos!
EXERCISE REQUIRES EATING AND BREATHING
Your mitochondria are miniature carbon-burning factories The fats, carbohydrates, and proteins that you eat every day are mostly made of carbon atoms linked together by what chemists call bonds Your mitochondria contain enzymes that break apart these carbon bonds; in the process, the energy is released and used to produce the ATP you need to survive and your muscles require in order to contract Oncetheenergyiscaptured,yourmitochondriahaveawastedisposalproblem:Whatarethey goingtodowithalloftheleftovercarbonatoms?Billionsofyearsago,theyfoundtheanswer!Combine theleftovercarbonatomswiththereadilyavailablegas oxygen andexpeltheproductasagascalled carbon dioxide Oxygenin,carbondioxideout,istheessenceofbreathing Voila!Problemsolved Notquite Unfortunately,thiseasysolutionfordiscardingcarbonintroducedanother,farmoreserious problem Oxygen is toxic; it must be handled very cautiously In general, the hemoglobin in your blood doesadecentjobofregulatingtheoxygenlevelsneartheindividualcellsofyourbodysothatyourcells havetheoxygentheyneedforremovalofthecarbondebris,butnotsomuchthattheyriskbeingkilled outright In response to all of this oxygen permeating your tissues, your body evolved numerous “antioxidant” systems that allow you defend yourself against the oxygen That is why they are called antioxidants; they prevent injury from oxygen Having lots of antioxidant systems allows us to live a long healthy life How long? It is currently thought that these antioxidant systems allow our species to have a maximum life span of about 117 years Obviously, most of us do not live that long Why? Part of the answer is that we eat all of the time, and move around all of the time, and therefore must keep breathing to remove the carbon debris; this makes us vulnerable to the consequences of oxygen permeating our body If you could only stop eating and breathing well, you would die There is no way out of this conundrum Remember what I said earlier: Because of your single-celled ancestor’s devilishdealwiththemitochondriabillionsofyearsago,youwilldie
Reactive oxygen species
Whileyouareeatingandbreathinginordertosurvivelongenoughtoreproducethenextgenerationof eaters and breathers (my future students), tissue-damaging molecules called reactive oxygen species (ROS) are constantly being produced by the mitochondria that live inside virtually every cell of your body. The story is not all bad; ROS are not always harmful. Oxygen has been around a very long time; during that time your body, as well as your pet’s body (my students always ask me if these rules also apply to their cats, dogs, birds, etc.), evolved some effective chemical tools to defend you from ROS unless, of course, you eat too much and move too much and therefore produce too many ROS. Unfortunately, too many ROS can overwhelm your natural antioxidant systems, slowly destroying your neurons as well as every other cell in your body. That is why you are always being encouraged to eat foods that offer additional antioxidant benefits, such as colorful fruits and vegetables. If you would like to see a visual representation of the actions of ROS please watch my TED talk here: https://www.youtube.com/watch?v=4SvkaK2Al0o&feature=plcp.
Think about the unbelievable irony of this process. The mitochondrial power plants that reside in quite large numbers in every cell of your body, particularly your muscles, are actively injuring those same cells that they reside within by the very process that keeps them alive A mitochondrion is the original Trojan horse and the ROS are Odysseus and his men hiding inside just waiting to emerge and do lots of damage to Troy (your body) It turns out that each species’ maximum lifespan may be determined by how many ROS are produced by the hundreds of mitochondria that live in each of their cells Thus, even at the level of individual cells, Cicero was correct: We are our own worst enemy Overall,foralltissuesinyourhumanbody,foralltissuesofallanimalsonthisplanet(exceptforarare genusof Monocercomonoides thatdonotcontainmitochondria),mitochondriaareaprincipalsourceof harmful ROS that underlies aging There is simply no way around this; we live on a planet bathed in oxygen
If you think this is bad news, the situation is much worse for males The biochemical processes that occur within the mitochondria are responsible for aging for both males and females; however, the mitochondria in females produce significantly less ROS than those from males The damage to mitochondrial DNA due to the elevated levels of ROS is four times higher in males than in females Thus,themitochondriainmalesagetheirhostsfasterthanthosewithinfemales Itshouldeminentlybe clear by now that we require lots of healthy mitochondria in order to stay alive! Women are protected from many of the negative actions of ROS by their higher levels of estrogen as compared to males (at leastuntilmenopause,whenmentendtohavehigherlevelsofestrogenthanwomen)
It’s all about the ovaries and their continued good health Ovariectomy abolishes the gender differences between males and females and estrogen replacement rescues, under most circumstances, from the ovariectomy effect The acceleration of age-associated processes and the increased
vulnerabilityoffemalestoalargevarietyofdegenerativediseasesthataccompanytheonsetofovarian failure at menopause are due to falling estrogen levels and increased vulnerability to elevated levels of ROS and pro-inflammatory proteins in the body and brain Menopause allows the indispensable act of respiration to reproduce the same pro-inflammatory, and quite harmful, environment in the brain of older women that is present in older males Due to these menopause-associated changes in body chemistry, women enter a phase of their life when they are at increased risk for disorders associated with extensive brain inflammation, such as depression, bipolar illness, and schizophrenia, as well as becomingmorevulnerabletodevelopingage-relateddisorderssuchasAlzheimer’sdisease,Parkinson’s disease,andamyotrophiclateralsclerosis
This symbiotic relationship with mitochondria that offers so many advantages also came with a huge price tag the ultimate death of any cell that possesses mitochondria That last statement requires some explanation The single most important factor that increases your chances of dying is causally relatedtohowmanydaysyouhavebeenalive Iknowthatstatementsoundstotallyobvious,butitdoes raise an important question: What is it that you do every day of your life that increases your chance of dying?Theansweristhatyoueatandbreathe everyday Eatingprovidesyourbodyandbrainwiththe energy stored within the carbon bonds that are contained within the fats, carbohydrates, and proteins that make up your diet Breathing brings oxygen to your mitochondria to carry away the carbon debris that forms when these bonds are broken apart This single critical activity, called oxidative metabolism or respiration, that is essential for your daily survival, is the most important factor that very slowly, minute by minute and day by day, ages you until you die That’s why consuming fewer calories every day is the only effective way to slow the aging process Eating antioxidant-rich fruits and vegetables is alsohelpful
The double-edged sword
The preceding paragraphs about the vital role played by mitochondria explain why any consideration about the benefits of exercise on your brain and body must consider the role of oxygen: your critical need for it while exercising balanced against its toxic effects in your body that cause you to age just a little bit every day. When you exercise moderately every day, your muscles, and the millions of mitochondria that dwell within them, will adapt to the increased intake of oxygen. Because of mitochondrialadaptation,exercisingpresentsitselfasadouble-edgedsword.Moderateexerciseadapts muscles to the consequences of the increased metabolism required to support it. The body has evolved the ability to adapt to increasing physical activity by increasing muscle size and strength while simultaneously improving our ability to obtain and deliver more oxygen to our tissues. In contrast, too much exercise, particularly for a long period of time, pushes metabolic demands to the point that your cells’ innate protective systems are overwhelmed and the increasing levels of ROS lead to accelerated tissue injury and aging. For the brain, as compared to the other tissues of your body, the abrupt increase in ROS levels associated with extreme levels of exercising is much more harmful. The brain is exceptionally vulnerable to increased ROS formation due to its own very high metabolic rate. Our fast, smartbrainscamewiththeirownevolutionarypricetag.
KGDHC
Fortunately, daily moderate exercise reverses the negative consequences of oxygen by reducing the production of one particularly nasty ROS, hydrogen peroxide. This is how. Mitochondria possess protective enzymes. One of these has the alphabetically challenged name KGDHC. KGDHC is readily induced by exercise and inhibited by hydrogen peroxide. When it is not functioning adequately, ROS production and hydrogen peroxide levels increase. This complex relationship between exercising, the production and utilization of energy, the mitochondrial requirement for a constant supply of oxygen, and the subsequentexercise-induced changesin muscle chemistryhasonlyrecentlybeen investigated. Thus,thestoryisstillevolvingasmoreknowledgeisgainedabouttheseprocesses.
Scientistshavediscoveredthatthegenesthatcontrolenergymetabolisminmuscleshavebeenhighly conserved across millions of years of evolution. Essentially, the better you negotiate your energy–oxygen interchange with your indwelling mitochondria while they provide you with the ATP that is required for movement, the healthier you are both physically and mentally. There are significant negative consequences in meeting the demands of continually exercising muscles. Fortunately, the activities of many different oxidative damage-repairing enzymes, such as KGDHC, are increased with exercisetraining.Butnotalways italldependsonthenatureoftheexercising.
The consequences of making ROS
Isexercisinggoodorbadforyou?Tofindananswer,weneedtoreturntotheprincipleofmoderation,a conceptthatIhavebeenemphasizingsincealmostthefirstpage.Thisconcepthasbeenaroundatleast since the time of the ancient Greeks, who wrote the inscription Meden Agan (μηδὲν ἄγαν) over the Temple of Apollo at Delphi. It warned “Nothing in excess.” Given that their culture emphasized sport, I would like to think that this warning also applied to their athletes. Then, as now, it is necessary to find therightbalance.Weshouldalldiscoverourpersonalbalancebetweengettingjustenoughexerciseto producebenefitwhileavoidingtheharmfulconsequencesofeatingandbreathingthatarenecessaryin
Here’s some surprising, and at first glance rather contradictory, good news: Regular moderate exerciseincreasestheproductionofROS Fortunately,thisleadstosomecriticaladaptiveandbeneficial responsesbyyourmuscles Thisadaptiveresponsehappensbecausemoderatelevelsofexerciseinduce thebirthofnewmitochondria Havingmoremitochondrialeadstogreaterlevelsofprotectiveenzymes such as KGDHC In contrast, extreme levels of exercise are not associated with the birth of new mitochondria or the presence of additional protective enzymes, thus exposing the brain and body to prolonged and toxic levels of ROS You might expect that having more mitochondria would lead to the production of greater levels of toxic ROS In fact, having additional mitochondria to assist with muscle contractionsduringregularexercisingmeansthateachindividualmitochondrionisallowedtoworkata lower respiration rate Essentially, there are more of them to share the workload Thus, each of them generates much lower levels of toxic ROS molecules Overall, thanks to all of your newborn mitochondria, as long as you maintain a steady regimen of moderate exercising, you do not produce as much ROS and the natural aging process is not accelerated significantly Notice what this conclusion does not predict: Exercising is not going to slow down normal aging Modest exercise, such as a daily strollinthepark,willsimplyallowyoutoagemoreslowlythanextremeexercising,suchasrunning10 mileseveryday Unlessyouhappentobeamale,because
IT’S NOT GOOD TO BE A MALE
Many of my male students participate in some form of daily exercise routine Every year I warn them about the consequences of too much exercising, but they are young and feel immortal and usually choose to ignore my advice Being a male, or more accurately having lots of testosterone circulating through the body, whether you have lots of big muscles or not, complicates the impact of exercise and energyproductiononmitochondrialfunctionandyourbody’shealth Testosteroneincreasestheenergy expenditure from muscle mitochondria, leading to an increase in the number of mitochondria within each muscle and an increase in the production of ATP Much of the energy used for the increased productionofATPisdrawnfromthebody’sstoredfat
So far, this all sounds OK But the hormone-driven mechanisms that control the metabolism of fat for energy have significant consequences for males Testosterone alters how males metabolize food and increases the amountof heattheir muscles produce during normalrespiration Testosterone,due to its effects on a specialized protein called uncoupling protein or thermogenin, makes the normal food-toenergyconversionprocessinmitochondriabecomeinefficient thatis,cellswastemoreenergyasheat, making men feel warm Lacking both testosterone and significant muscle mass (typically), women tend to produce less body heat from their food; consequently, it is usually much harder for women to lose weight than it is for men The male body, particularly all of those muscles, is capable of wasting a considerable number of consumed calories as body heat This explains why the principal method of dietingformanyofmymalestudentsistoeatanythingtheywantandthenexerciseoffthecalories Or, they could do nothing at all: Males, to the chagrin of many females, can lose weight by simply sitting still In contrast, women, who lack the mitochondrial uncoupling actions of testosterone, are forced to loseweighttheold-fashionedway,bynotconsumingasmanycalories
Formales,wastingcaloriesinordertoproduceheathassomenegativelong-termconsequences First of all, males need to consume more calories per day than do females; consequently, males generate more harmful reactive oxygen-free radicals ROS These ROS are quite harmful to the body and negativelyaffectmen’shealthandreducetheirlongevitycomparedtowomen It’s not just human males who have reduced lifespans due to eating and breathing Human males do notnecessarilyleadmorerecklesslivesthandofemales,atleastnotafterage30 Malesof all species, including spiders, flies, and the birds and the bees, never live as long as females of all species This is trueevenforspecieswithaveryshortlifespan,suchasafly Malefliesofonespecieshaveanaverage maximum lifespan of five days; the females of the same species have an average maximum lifespan of sevendays Incontrast,womenwastelessenergyasheat,needtoconsumefewercalorieseverydayin ordertosurvive,andproducefewerROS,allofwhichbenefitstheiroverallbrainhealthandlongevity If ROS are so harmful, why does your body produce them? Because you have no choice If you have stoppedmakingROS,youareprobablydead
