Some naysayers might point to genetics and claim that these people who become fat from “yoyo” dieting just had “bad genetics” and were going to become obese regardless. 

However, this doesn’t make sense from a teleological point of view. Obesity is a very new problem. It only started popping up in the 1960s, yet less than 60 years later, it’s a full-blown epidemic. 

Did our genetics suddenly change in the last few generations? Very unlikely, and data doesn’t support that. 

A study examining homozygous twins (literally the same DNA code) and their experiences with dieting throughout their lifetime revealed a shocking revelation: the twin that dieted more often tended to be fatter even though their genetics were identical.*1 

How is it possible that people who diet more often actually end up fatter? My opinion, based on data is that it’s not dieting itself that makes some people fatter, but how most people attempt to lose weight, which often is in a weight cycling aka “yo-yo” dieting manner. 

Dieting, you see, is treated by the body like controlled starvation, and it triggers some pretty serious self-defense systems in the body. These self-defense systems are activated as a three-pronged defense to: 

1. Defend – Prevent further weight loss (during the diet aka weight-loss plateaus) 

2. Restore – Increase the rate of weight regain once sufficient energy is consumed (post-diet) 

3. Prevent – Decrease the probability of losing weight in the future.*2 

Figure 2: The body’s 3 pronged self-defense system. 

Prong 1 is the “defend” prong where metabolism slows during caloric restriction to defend against starvation. 

Prong 2 is the restore prong where hunger exceeds the energy required to restore energy balance and systems that promote fat storage are enhanced while under caloric restriction. 

Prong 3 is the prevent prong where the body may increase the fat cell number if weight is regained too rapidly to defend against future energy deficits.

An obesity researcher named Paul MacLean has referred to this self-defense system in several of his research publications, stating that:

Weight loss awakens the body’s defense system in a manner that is persistent, saturated with redundancies, and well-focused on the objective of restoring the body’s depleted energy reserves… 

Any weight loss strategy that fails to acknowledge and plan for this emerging metabolic influence is likely to have little success in facilitating long-term weight reduction… 

To ensure success, the regain prevention strategies will likely need to be just as comprehensive, persistent, and redundant, as the biological adaptations they are attempting to counter. *3*4 

Why would our bodies evolve to make it difficult to lose weight and easy to regain it? 

Well, if you are deliberately placing your body in an energy deficit by attempting to diet frequently, what signal are you sending your body? 

You are telling your body that energy is sparse and that it needs to defend its energy stores from further depletion as stated in point one. 

Therefore, when the body comes across an adequate food supply, it will do its absolute best to capture as much of that energy as possible so that the potential for starvation is lower in the future, as stated in point two.

 Finally, your body would want to defend its restored energy reserves even more aggressively against depletion in the future since it has already experienced “famine,” as in point three.

You might be thinking, “This doesn’t make sense.” After all, energy is plentiful these days, and we don’t have to worry about starvation.

 I can walk right down to McDonald’s and shovel down a thousand calories for under $3, so why would my body ever think it was going to starve?

 Try to think about things from an evolutionary perspective. Plentiful food for most people even in western society has only been a reality for around 100 years. 

So while our circumstances have changed, our genetics haven’t. Our genetics are lagging behind by several thousand years. Our very DNA still remembers famine from thousands of years ago, and it’s still hardwired to protect us from starving to death. 

You’re here today reading the pages of this blog because our ancestors had the right DNA milieu to resist killers such as famine, disease, etc. 

In the case of resisting famine, that meant we required a mechanism that could protect us from starvation—our metabolism slowed down when the food supply was limited. It also meant having thrifty enough genes so that when food was sufficient, they could efficiently store large amounts of the energy consumed. 

We want to emphasize that when we refer to “energy,” we are referring to the calories contained in food. A calorie is quite literally a measurement of energy. When we refer to energy depletion or energy storage, that is essentially the same thing as body fat loss or storage, since adipose tissue (aka body fat mass) is by far the largest form of stored energy in the body. 

Therefore, when you diet and cause energy depletion, it makes sense that the body would activate a defense network with the purpose to make energy production and energy storage more efficient.

You may read the word “efficient” and think it’s a good thing. Most times when we hear or read that word, there’s a positive connotation attached to it. Not with regards to energy storage or production. Think of fuel efficiency. 

If your car is energy efficient, it can run a long way on a tank of fuel. If the goal is fat loss, however, you want to be as inefficient as possible. 

Think of your adipose/body fat stores (energy reserves) as a tank of fuel. You don’t want to be a bicycle that takes forever to burn through a tank of fuel, right? (well, you know what I meant is, that car which has milage like anything is what I referred to here)

 You want to be an enormous gas-guzzling SUV that burns through fuel quickly. Further, when it comes to preventing the recuperation of body fat, you don’t want your body to be efficient at energy storage. 

Using our car analogy again, you also wouldn’t want a car with a large fuel tank. If the fuel is our energy and the tank our potential fat stores, then you wouldn’t want it to fill up efficiently. 

You’d want a tank that leaked and wasted fuel so that it was more difficult to fill up, not an efficient tank that easily stored all the energy you pumped into it. 

In this way, one of the body’s major self-defense systems is to become more efficient with energy handling to prevent depletion of energy (adipose/body fat) stores and also refill them as efficiently and quickly as possible.

*1 (2011, August 9). Does dieting make you fat? A twin study. – NCBI – NIH. Retrieved September 4, 2018, from https://www.ncbi.nlm.nih.gov/pubmed/21829159

*2 (n.d.). Biology’s response to dieting: the impetus for weight regain. – NCBI – NIH. Retrieved September 4, 2018, from https://www.ncbi.nlm.nih.gov/pubmed/21677272

*3 (n.d.). Biology’s response to dieting: the impetus for weight regain. – NCBI – NIH. Retrieved September 12, 2018, from https://www.ncbi.nlm.nih.gov/pubmed/21677272

*4 (n.d.). The role for adipose tissue in weight regain after weight loss.. Retrieved September 12, 2018, from https://www.ncbi.nlm.nih.gov/pubmed/25614203

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