Arya M. Sharma, MD

One of the most common notions of why obesity is so rampant today is because most of us carry in us the genetic ability to avidly take up calories when they are around and use them sparingly when they are not.

This notion has been called the “thrify genotype” and has been credited with allowing our ancestors to make it through the millenia of feasts and famines, while being blamed for the obesity epidemic today.

But does the genetic ability to become fat really bestow a survival advantage?

This question was addressed by David Pierce and colleagues from the University of Alberta in a paper just published in the International Journal of Obesity.

In this study, young genetically obese and lean-prone rats were exposed to a rigorous regimen of sparce food and ample exercise (wheel running).

Although the obese and lean-prone rats started out at the the same initial body weight, the obese-prone rats survived twice as long, and ran three times as far, as their lean-prone counterparts.

In addition, the obese-prone animals were able to maintain blood glucose and fat mass, whereas lean-prone rats quickly depleted these energy reserves. Judging by the corticosterone concentrations, the obese-prone rats appeared far less stressed by the survival challenge than their lean-prone counterparts.

This study clearly demonstrates that (at least in rats), carrying the genes for obesity confers a huge survival advantage during severe food restriction and strenuous exercise. In fact, even unders these “thrifty” conditions, the obesity prone animals were able to conserve their fat mass by being far more efficient (energetically) than their lean counterparts (same amount of work for fewer calories).

Thus, these findings not only support the hypothesis that an obese-prone genotype provides a substantial fitness advantage when the going gets tough but also shows why the same amount of dieting and exercising simply does not lead to the same amount of weight loss for everyone.

I guess it’s clear who the survivors of the next famine will be…

AMS
Edmonton, Alberta

With all the talk of “thrifty genes” and how our “hunter-gatherer genome” is overwhelmed by the “obesogenic” environment, it may be time to revisit my favorite theories about the “Natural Laws of Weight Gain“.

This is something I came up with almost 10 years ago and have used in a lot of talks over the years. I’ve always wanted to put these ideas into a book but somehow never got around to it.

Simply stated, my Six Natural Laws of Weight Gain are as follows:

1. Always eat when food is around
2. Always go for the gravy
3. Always eat as fast as possible
4. Always eat as much as possible
5. Don’t move if you don’t have to
6. When fuel runs short, turn down the furnace

If anyone is thinking, “hey, that’s me”, you’re probably not alone (in fact it’s me too!).

If you take a minute to think about it, you’ll probably recognize just how deeply these Natural Laws are engrained in our biology and culture and may realize how we’ve actually designed much of our environment to accommodate these laws.

Suddenly terms like “mindless eating”, “fast”food restaurants, “all-you-can-eat” buffets, “poutine”, “super-size it” and “couch potato” take on a whole new meaning.

While through the millennia of evolution these Natural Laws guaranteed the survival of our species, in our current obesogenic environment, they also pretty much guarantee weight gain.

As I have often pointed out in my talks: “In today’s obesogenic environment, people have to develop “abnormal” behaviors to avoid gaining weight”.

Doing things that came “naturally” to most of us is a surefire recipe for weight gain - in today’s enviroment, fighting obesity literally means going against our “nature”! No wonder it is so hard to do.

OK, I realize that by now some of you are screaming that this must be wrong, that I am grossly oversimplifying the complex psychosociobiology of obesity, and that I am just providing obese people with an easy “excuse” to blame it all on nature.

Of course I realize that in reality things are way more complex and that there are many paths that lead to obesity ranging from childhood molestation to antipsychotics or from genetic defects to endocrine abnormalities (the list of possible causes if far longer than you may think!).

Nevertheless, I do believe that perhaps with the exception of such “special causes” the Natural Laws do provide a reasonable and useful framework for thinking about the root causes of the current obesity epidemic.

So in the next couple of weeks, I will be occasionally revisiting this theme and hope to explore some of these laws and how they apply to our current dilemma.

Perhaps the title of my book should be: “The Six Natural Laws of Weight Gain and How to Break Them“!

I wish someday to actually find time to write it - I could probably have a lot of fun with this.

AMS