You want to bitch and whine about how you’re genetically programmed to be fat? Then go do it somewhere else. People who adopt the victim mentality royally piss me off, so if you’re one those, then fuck off. This is not a book that preaches fat acceptance. I won’t cater to your “poor me” attitude. I won’t tell you what you want to hear. I will tell you the truth, and even if evolution played a joke on you, I will still offer hope. Obesity is a major problem and a leading cause of death, so you shouldn’t just accept it. You should do something about it.

Many fat acceptance authors preach what amounts to “You can’t win, so don’t try.” Don’t pay attention to such crap, because you can win. You may never have a hope at getting six-pack abs. You may never look like a fitness model. However, you CAN achieve your maximum genetic potential. Like the old U.S. Army slogan said: “Be all that you can be.” Don’t be a victim and don’t make excuses. Just do what you can with what you have. Your body is the only one you’ve got. Even if you own a mint-condition 1966 Corvette Stingray, your body is still your most prized possession, so stop treating it so poorly.

If you found the above statements offensive, then you’re welcome.

Maybe it’s your genetics and maybe it’s not. Maybe it’s pie. Maybe it’s pizza. Maybe it’s beer. Maybe it’s the fact that you scarf all three while your ass is glued to the couch. You’ll never find out what you’re capable of if you’re not willing to work hard and be adaptable. Maybe you suck at fat loss but build muscle easily, so you would want to increase your aerobic activity and focus more on creating consistent caloric deficits (much more on that later). That’s just one example. Pay attention to what works for you and what doesn’t. Like I wrote earlier, be an active participant in the creation of your program.

If you are interested in broadening your mind a little, then lets get down to the nasty business of explaining the genetics of obesity and response to physical activity from a non-geneticist.

This could be painful.

Researchers are well aware that both genetics and familial environment play important roles in who we are and who we become which is why there have been numerous studies that control for the nurture factor by utilizing twin and adoption studies to single out genetic causes for specific outcomes.

There is debate on this subject because some studies have shown that a portion of the population is essentially untrainable. Before you say, “Well, then screw it!” and throw this book on the fire, allow me to explain further about this research and what it means.

Dr. Claude Bouchard is one the most respected and well-known researchers in the field of the genetics of obesity and physical fitness. Bouchard was leader of the HERITAGE Family Study which, during its first phase, took 481 healthy but sedentary Caucasian subjects from 98 separate families and tested their aerobic capacity, put them on a lab-supervised training regimen for the next 20 weeks, and then re-tested them.³

There is no question that some people will respond better to training than others. You may discover that working hard gets great results. You may start running and find that you suck at first, but after a few weeks you can go further and faster than when you started. Conversely, you could be a low responder and have to work at it for a long time before you see improvements in your aerobic ability.

There is a definite connection between genetics and living longer, but not in the way you may think. There do not appear to be any specific genes that are directly associated with longevity, rather the opposite is true. Some unfortunate people have deleterious heritable traits that lead to premature death from any number of diseases or detrimental effects such as high cholesterol or a tendency towards obesity or cancer.⁶ This provides confirmation to what I wrote in Chapter 3 – that people who die at an earlier age usually do so because of disease (or an accident), but those who live significantly longer than the average life expectancy remain disease free until they near the end of their lives.

Although the vast majority of cancers are lifestyle related, there may be some diseases that you are at a much higher risk for because they’re hard-coded into your DNA. You might be a ticking time bomb, but if there is any hope to delay things going boom it is living a healthy lifestyle. As I’ve already shown, even if you have preprogrammed susceptibility to something like heart disease you can extend your life by keeping your weight at a healthy level, controlling cholesterol (with pharmaceutical help, if necessary), exercising regularly and intensely, avoiding smoking, limiting alcohol intake and consuming a healthy diet. You may be programmed to die early, but you can fight a valiant delaying action and stretch out the time you have left, probably by a long time.

A 1988 article published in the American Journal of Clinical Nutrition found that heredity had negligible effect on overall caloric intake. This means the total amount of Calories you take in aren’t genetically predetermined. However, the study did find that there is a 20% degree of heredity when it comes to percentage of carbohydrates and fat in a person’s diet, and an 11% genetic effect on protein intake.⁹ In other words, from a genetic perspective you have complete control over how much food you eat, and a large degree of control over what kind of food you eat. 

Cholesterol and Genetics

In tackling the data for this subject the best assessment I can come up with regarding genetics and cholesterol is that the link is significant. According to Claude Bouchard, “it has long been recognized that there are considerable differences among individuals in response of serum cholesterol to dietary cholesterol.”¹⁰ Some people can eat piles of butter fried shrimp battered in egg yolks and served with a side of bacon and have minimal impact on their serum cholesterol levels. Some others catch a whiff of sizzling bacon and their level spikes. I’m closer to the latter. Right now I keep my cholesterol levels in a safe range by getting a crapload of aerobic exercise and watching my diet. That may not always be the case. I get it checked annually to keep on top of it because high cholesterol can lead to heart disease, and it can be treated with drugs.

Question: What is a somatotype?

Answer: Who gives a shit?

Seriously, these are vague labels that don’t mean bugger all in real life. I’ve been working out for fifteen years and couldn’t say for sure what mine is. I don’t burn fat easily; I have to monitor Calories and do lots of aerobic exercise to stay slim. I don’t build muscle effortlessly either. I’ve worked my ass off to get the moderate amount of muscle I have. I’m not genetically programmed to be a bodybuilder (like I care).

Anyway, I’ll relay the theory, but in my opinion somatotype is something that you shouldn’t worry about because your body type is what it is.

1. Ectomorph: “characterized by linearity and fragility, along with poor muscle development and a predominance of surface area over body mass.”¹¹ Linearity and fragility? I guess that’s the scientific term for “pencil neck.”
2. Mesomorph: Allegedly these folks are the genetic lottery winners. I’ll admit that I look like one if you go by the definition, but I don’t think I am a natural meso because my body resists fat burning like a mofo and I don’t build muscle without serious effort. I look like this because of hard work and that’s it. Mesos are “characterized by the predominance of muscle, bone, and connective tissues, so that muscles are prominent with sharp definition.”¹² Uh, that description may fit me now, but it sure didn’t when I was a fat ass at 25-years old.
3. Endomorph: Also known as “Sucks to be you.” The text book description is: “characterized by the predominance of the digestive organs [WTF?] and by roundness and softness of contours throughout the body.”¹³

Knowing your somatotype isn’t necessary in the grander scheme of getting in shape. It’s just a scientific label so I advise you to care less. It’s like body fat percentage; a member of my advisory committee asked me if I wanted to get a hyper-accurate body fat measurement using the university’s underwater weighing tank, but I declined because it’s not a number I care about. Cholesterol levels are numbers I care about. BMI is a number I care about. How many abdominal muscles I can see when I look in the mirror is a number I really care about.

Think about it. A couple of years from now when you’re strolling down the beach and some babe checks out your six pack she’s not thinking, Wow. Check out that mesomorph. I bet his body fat is below seven percent.

When it comes to the question of whether or not BMI is a heritable trait, we are one-hundred percent certain that we’re just not sure. Estimates range from as high as 90% heritability to almost zero.¹⁴ Yeah, whatever.

The problem is that most studies have a hard time separating the effect of genes and environment. Nevertheless, some determined researchers have utilized twin and adoption studies to try and get to the bottom of it. Comparing MZ twins (monozygotic, which means identical) raised apart with MZ twins reared together allows for some measure of control over confounding influences of a shared family home.

• Correlation for MZ twins is 74%
• Correlation for DZ twins is 32%
• Correlation for non-twin siblings is 25%
• Correlation for parent to offspring is 19%
• Correlation for adoptive relatives is 6%¹⁷

The interesting note here is that DZ twins have a 7% higher correlation than do non-twin siblings. DZ twins have no more shared genes than do siblings born years apart, yet the influence of a shared womb and being the same age growing up together has influence on BMI.

If you have a fat identical twin I could see how this information might be depressing. Otherwise, the news is pretty good because the parent to offspring correlation is only 19%. You a not a clone of any one parent, but a mixture of the two, and genes have a way of mixing in unexpected ways, sometimes to your benefit. Every male I know of in both of my parents families is balder than Captain Picard, yet I still have my hair.

Obesity is a complex trait. According to Dr. Stephen Roth:

“The bottom line is that both genetic and environmental factors (and their interactions) are likely to explain obesity in any one person… the human genome is not adapted to a sedentary environment, having evolved over centuries of hunter-gatherer living, so that low levels of physical activity are harmful…”¹⁸

And Dr. Bouchard had this to say (in PhD speak) about whether or not obesity is inherited:

As I mentioned at the beginning of this chapter, the epidemic of obesity in the developed world has nothing to do with genetics. Only a small portion of the populace is genetically challenged when it comes to maintaining a healthy body weight, and these genes haven’t changed in millennia. If I wanted to be nasty I could say it’s your fault that you’re fat, but that isn’t entirely true. Genetics may play a role, but what is more likely is the role played by our changing society. We have machines to do the vast majority of our labor and easy access to an overabundance of highly palatable food. No wonder so many people are overweight when we don’t have to do anything physical and there’s lots of yummy chow to be had.

Prior to the 20^th century people didn’t have a choice but to be thin because of the amount of daily labor required just to survive, and the fact that food was in shorter supply. There was a direct relationship between the amount of food people consumed and the amount of work they had to do to obtain that food. Not only that, but the food they did have didn’t taste as good and took a lot more preparation than going through the McDonald’s drive-through or hitting the convenience store for a bag of potato chips and a pint of ice cream. Our ancestors didn’t have to think about watching their weight because circumstances watched it for them.

A prime example of how circumstances affect BMI is that of the Pima Indians. A group of Pima Indians in Arizona were compared with Pima in an impoverished and remote area of Mexico. The two groups have a shared genetic background (a background that in theory is programmed to gain weight easily), but their circumstances are not at all alike. The Arizona Pima have a lifestyle that requires far less manual labor and provides access to ample high-Calorie foods. As a result, the Arizona tribe has one of the highest rates of obesity and type 2 diabetes in the world. By contrast, the Mexican Pima tribe had an average BMI of 25.9 for women (just barely “overweight,” and far from “obese”) and 23.6 for men (well within the “normal” range). The Mexican Pima live a spartan existence with high levels of physical activity and modest caloric intakes. As a result, they are proof that even though programmed to be overweight (a “thrifty gene” survival response developed over thousands of years of living through lean times),²⁰ these Pima remain at healthy BMI levels because of their lifestyle. Granted, that lifestyle is one of poverty and wasn’t made by choice, but from a genetic perspective it provides proof that no one is destined to be fat, some people just have to work harder at controlling their weight. For an unlucky portion, they have to work exceptionally hard.

Genetics can play an influential role in a person’s level of physical activity. The important thing to note here is that physical activity, technically speaking, is not the same thing as exercise. Nevertheless, if you have the genes they can be of tremendous benefit.

My daughter is a twitchy little thing. At seven-years old she has impressive muscularity and visible abdominals. I’m not sure where these genes came from, but it might just be one of those odd mixings that is akin to me still having hair. I can tell just by living with her that she is genetically programmed to be active because she prefers to be mobile as much as possible (No, she doesn’t have ADHD – she can concentrate just fine when she wants to and does well in school). Anyway, there are many people who are “fidgeters” and this is largely an inherited trait. They have a difficult time sitting still and as a result can burn hundreds of more Calories per day over a non-fidgeter (studies have measured this difference in a respiratory chamber).²² Any time my daughter comes to sit on my lap to watch TV within about three minutes it turns into a wrestling match. 

I’m not a fidgeter; I can happily glue my ass to the couch and watch a Lord of the Rings marathon getting up only to grab another beer, dial for pizza, or get rid of some processed beer. I rarely have a burning desire to jump up and go to the gym or go for a run – I have to consciously decide to do it. High-energy fidgeters are more likely to be active because they don’t like sitting still.²³

Now either you are a fidgeter (or hyper, on-the-go, vigorous etc.) or you aren’t. I’m guessing you fall into the “aren’t” category, which makes motivation to exercise and careful planning of activity that much more important.

Like obesity, muscularity, trainability and performance can be inherited traits. Heredity plays a significant role in the amount of fat-free mass (FFM) you have. High percentage of FFM is a good thing because it means that you have a lower percentage body fat. Being that muscle tissue makes up the majority of FFM, then a genetic connection is easily made. In fact, studies have shown a higher genetic correlation to FFM than to fat mass and percentage body fat.²⁴

Your body has a definite set point of how much muscle you can potentially build, both cleanly and using anabolic steroids (which I strongly discourage). There is an upper performance limit for just about anything you try to do with your body. Gold medal Olympians train rigorously, but also have superior genetic abilities that help make them better than everyone else at their sport. They are genetically programmed to be high responders to training and to excel in a specific area or areas of sport. The marathoners can’t lift heavy weights and the powerlifters can’t run all that far. Although their training plays a role, genetics are the key factor in these types of differences. According to Vassilis Klissouras, “Training can not modify a phenotype [a trait that is expressed as a result of both genetic and non-genetic factors] beyond a limit set by the genotype and will never erase individual differences due to innate ability.”²⁵

If I had to guess, I’d say I’m pretty middle of the road between an endurance athlete and a power athlete. I’ve trained myself to be pretty good at both (not in real competition, but compared to the typical middle-aged guy). I can run a half marathon in about an hour a fifty minutes, which isn’t bad, and my highest one-rep max on bench press is 315 pounds. I’ve never yet run a marathon, and I don’t plan to in the near future because it goes against my visual goals of having high muscle mass. If I decided that marathons were my thing then to get good at it I’d need to drop a bunch of muscle because the extra weight would slow me down. If I trained hard for a couple of years I think I could get my time to about three hours and thirty minutes, and for my age group this still isn’t fast enough to qualify for the Boston Marathon.

The type of athlete you can become is determined partially by your muscle fiber distribution. There are two types of muscle fibers: Type I and Type II (Type II is divided into two subtypes, but the difference isn’t significant enough to warrant exploration in a “getting in shape” book).

These are also known as slow-twitch fibers (ST), a name I will use from now on. These are small in size and programmed for endurance. They are the aerobic muscle fibers that, in a manner of speaking, don’t reach exhaustion – at least not for a long time. These are the ones you use when you walk, run, swim, bike etc.²⁷

The fact that they are small is significant. Endurance athletes who don’t strength train are slim and wirey. They have muscular definition, but their muscles lack much bulk. They also have less short-burst power.

These ones are the fast-twitch fibers (FT), are larger in size and quickly exhausted of their energy because they are used for short-burst power. While you can run for a while (well, maybe not yet, but we’ll get you there), the FT fibers have little stamina. These are the ones you are using while weightlifting, and the dynamics of FT fibers is the reason why you can only lift heavy weights just a few times.²⁸

But they’re big, and when you work them, they grow bigger. Hoo-raa.

There is a moderate heritability factor to muscle fiber distribution, and I could relay a bunch of percentages pulled from a text book, but I’m not sure there is much point in doing that anymore. After all, I didn’t know any of this stuff when I got in shape, and I’m not so sure you need to either. The fact is that when it comes to muscle fibers, what you’ve got is what you’ve got and who cares how that came to be?

However, your own past can give you a clue as to your future. Were you a good athlete in your high school days, but then let yourself go after graduation? Were you more of a sprinter or a distance runner? What kind of sports were you good at as a teenager? Were you good at short-burst power sports, or endurance sports, or perhaps both? Or were you like me and sucked at everything?

Back when you could see your muscles, how did they compare to other guys your age? If you looked pretty good at 18 then you can reclaim that physique and build on it. If you struggled with your weight even as a child then your challenges with fat loss will be greater. If you were thin as a rail then you likely will burn fat easier than you will build muscle.

It sounds lame and cliché to say so, but you’ll never know what you’re capable of until you try.

Okay, that was indeed painful. If you thought it was hard to read, imagine what it was like for a non-geneticist to write. I had to slog through some of the most academic-oriented geek speak and then translate it into normal English. Did you note in the section on trainability that I mentioned Vassilis Klissouras refuted claims about a segment of the population being untrainable, but I didn’t provide details regarding his arguments as to why? Well, here are his exact words:

I digress. The point is that genetics can play an influential role in body type, trainability, predisposition towards exercise and eating habits, as well as overall obesity risk.

Notice that I wrote “can play an influential role.” This is far from being an absolute.

Because you are now aware of how genetics can affect your efforts to get in shape, you can use that information to your benefit. The primary takeaway from this chapter is: be adaptable. Pay close attention to what works and what doesn’t and work on improving in areas that you are weak while taking advantage of areas in which you are strong.

It can be hard to determine exactly what genes you have. Even men who are programmed to lose fat and build muscle easily can look like blobs if they are donut-loving couch potatoes. Maybe your genes will be your friend and maybe they won’t be. Like most things in life, the variety of expression of the human genome distributes people along the bell curve. All men are NOT created equal. Maybe you are programmed for power over endurance or maybe the other way around. Maybe you have potential to be good at both. Maybe you suck at both. Not everyone gets to be an astronaut when they grow up, or an Olympic athlete.

As I wrote at the beginning, it is all about achieving your maximum genetic potential, no matter what that potential may be, and you won’t find out what it is while watching TV. Remember that heritability is not a prison sentence unless you decide to make it one.


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1. Katherine Flegel et al., “Prevalence and Trends in Obesity among U.S Adults, 1999-2000,” Journal of the American Medical Association, 288 (14), October 9, 2002, p. 1724.
2. Claude Bouchard, (Ed.), “Introduction,” Physical Activity and Obesity, (Champaign, IL: Human Kinetics, 2000), p. 13; Stephen Roth, Genetics Primer for Exercise Science and Health, (Champaign, IL: Human Kinetics, 2007), p. 57.
3. Claude Bouchard et al., “Familial aggregation of VO₂ max response to exercise training: results from the HERITAGE Family Study,” Journal of Applied Physiology, 87, 1999, p. 1003.
4. Ibid., pp. 105-107.
5. Vassilis Klissouras, “The Nature and Nurture of Human Performance,” European Journal of Sport Science, 1 (2), June 1, 2001, p. 1.
6. Claude Bouchard et al., Genetics of Fitness and Physical Performance, (Champaign, IL: Human Kinetics, 1997), pp. 110-111.
7. Preetha Anand et al., “Cancer is a Preventable Disease that Requires Major Lifestyle Changes,” Pharmaceutical Research, 25 (9), September, 2008, p. 2097.
8. Albertine Schuit, et al., “Physical Activity and Cognitive Decline, the Role of the Apoliproprotein e4 Allele,” Medicine & Science in Sports & Exercise, 33 (5),  May 2001, p. 775.
9. Louis Pérusse et al., “Familial Resemblance in Energy Intake: Contribution of Genetic and Environmental Factors,” American Journal of Clinical Nutrition, 47 (4), April 1, 1988, p. 633.
10. Bouchard et al., Genetics of Fitness, p. 141.
11. Ibid., pp. 153-154.
12. Ibid., p. 153.
13. Ibid., p. 153.
14. Ibid., p. 182.
15. Ibid., p. 183.
16. Ann Hasselbalch et al., “Common Genetic Components of Obesity Traits and Serum Leptin,” Obesity, October 16, 2008, p. 1.
17. Hermine Maes, et al., “Genetic and Environmental Factors in Human Body Weight and Relative Adiposity,” Behavior Genetics, 27 (4), July, 1997, p. 325.
18. Roth, Genetics Primer, p. 57.
19. Bouchard et al., Genetics of Fitness, p. 206.
20. Caroline Fox et al., “Is a low leptin concentration, a low resting metabolic rate, or both the expression of the ‘thrifty genotype’? Results from Mexican Pima Indians,” American Journal of Clinical Nutrition, 68, 1998, p. 1053; Bouchard (Ed.), Physical Activity and Obesity, p. 13.
21. Bouchard et al., Genetics of Fitness, p. 190.
22. Ibid., p. 124.
23. Ibid., pp. 124-125.
24. Ibid., pp. 226-227.
25. Klissouras, “The Nature and Nuture,” p. 1.
26. Craig Sharp, “The Human Genome and Sport, Including Epigenetics and Athleticogenomics: A Brief Look at a Rapidly Changing Field,” Journal of Sports Sciences, 26 (11), September, 2008, pp. 1129-1130.
27. Bouchard et al., Genetics of Fitness, p. 224-227.
28. Ibid.
29. Klissouras, “The Nature and Nuture,” p. 7.