The mechanics of gaining and losing fat, part 1

When I wrote my original post about weight loss I didn’t want to go into too much of the specifics of why eating a low-carbohydrate high-fat diet works. I did mention blood sugars, their effect on insulin, and gave reasons why it’s vitally important to control the insulin levels. However, I purposefully didn’t go into the very specifics of how fat accumulation works. It’s time to change that.

Can wearing sweaters make you fat? Yes, if you follow the logic of the caloric balance hypothesis.

This article wouldn’t be possible without the brilliant Good Calories, Bad Calories by Gary Taubes, who spent five years studying medical literature and research related to metabolism, nutrition, and obesity starting from mid 1800s. He then summarized his findings into one book that covers the journey of how this field of science has evolved, and how we ended up from very controversial hypotheses to government-enforced nutritional guidelines.

In this first part I’ll focus more on the conventional wisdom and its shortcomings in explaining why people become overweight. I hope you enjoy the ride!


The role of thermodynamics

We have become obsessed with calories. Eat less, exercise more and the weight is supposed to melt away. This makes logical sense, doesn’t it? How could you even possibly become overweight if you eat less than your body consumes? The basal metabolic rate (meaning how much your body consumes energy at rest) for most men is around 1900 kcal/day range, whereas for women it’s maybe 200 kcal/day less. So munching more than 2000 kcal/day while doing little to no exercise would mean you become fatter, whereas on the other end of the spectrum if you exercise well and keep the caloric intake below, say 1600 kcal/day, you should be losing weight.

The formula for this caloric balance hypothesis is as follows:


Change in weight = Calories IN – Calories OUT


If Calories IN is more than Calories OUT, then an increase in weight ensues. Whereas if Calories OUT outweigh Calories IN, then one should be losing weight. The fundamental principle behind this thinking is the First Law of Thermodynamics.

The first law states that energy cannot be created or destroyed. It can only be transformed from one form to another. From the perspective of weight gain this means that the excess calories you ingest will be either stored as fat, or dissipated as heat through thermogenesis. It doesn’t matter if those calories come from fat, protein, or carbohydrates, you cannot avoid the laws of thermodynamics.

A fundamental flaw in this thinking, however, is that the first law is valid only in closed systems, and we happen to live on planet Earth, not in an isolated box. A human organism is:

  1. Not in thermal equilibrium with its environment (our body temperature is not the same as the temperature around us).
  2. Capable of significant mass flows (e.g. respiration).
  3. Capable of sequestering entropy (e.g. protein synthesis).


In other words, the first law does not tell whether or not excess calories will be stored as fat. If it held true, wearing sweaters would make us fat as it would reduce our bodies’ need to produce heat, and thus reduce the total energy expenditure. The above thinking would also imply that we consume calories for the sole purpose of generating heat, rather than e.g. breathing, using our muscles, digestion etc. In reality heat is a waste product of our normal metabolic functions.

Another fundamental problem in this caloric balance theory is that it assumes that Calories IN and Calories OUT are independent variables. This means that if your basal metabolism is 1800 kcals/day and you eat 1600 kcals/day you’d be losing weight since your Calories OUT part is higher than the Calories IN part. However, in reality when you reduce the Calories IN, the Calories OUT decreases as well. Eat less and your body will also consume less energy.

Perhaps the significance of this becomes more evident when presented the other way around; if your Calories IN part is more than your basal metabolism, your body will also compensate on that and increase its energy expenditure. Another result of this compensation mechanism is that if you increase Calories OUT by for example exercising, you will become more hungry and need to eat more to satisfy your appetite.

So if you eat too much and your body will increase energy expenditure to compensate for it, then why do people become overweight? I’m afraid you need to wait until my next post to find the answer.


How it all went wrong

Those of us born after the 60’s probably are not aware of the starting point of the low-fat craze. So would it surprise you to know that the low-fat thinking didn’t become mainstream until 1970’s? Before the Second World War it was public knowledge that carbohydrates, and especially sugars, are fattening.

In the 1970’s the US government started publicly announcing that low-fat high-carbohydrate diet is good for you, and that you should be especially worried about saturated fat intake. However, there has never been conclusive evidence that would support the dogma of low-fat diets being healthy. Since the 1970’s hundreds of millions of dollars have been spent on studies trying to prove this hypothesis, but to no avail.

In science hypotheses are tested by performing experiments. The results of an experiment are then evaluated in light of the hypothesis under scrutiny, either confirming the hypothesis or disproving it entirely or partially. Even if the results of an experiment contradict a hypothesis, it does not necessarily mean that the hypothesis should be discarded as wrong. Our ability to perform experiments is limited by conditions such as technology, time, and resources which all affect the reliability of the results.

However, when a hypothesis is being tested over and over again by numerous researchers, and in numerous experiments, while the research results consistently give inconclusive evidence in light of the hypothesis, it should be time to re-evaluate the hypothesis itself. In the field of nutrition, health, and obesity research this has not been the case.

One of the underlying problems is that governments have become so invested in the low-fat belief that it is very difficult to get funding for research that would, in essence, aim to disprove or at least challenge the current national dietary recommendations.


Problems with the caloric balance hypothesis

In addition to research having failed to prove the caloric balance hypothesis, the hypothesis itself has other major shortcomings. It does not provide any explanation to the following facts.If the caloric balance hypothesis was true, then:

  • Why is obesity more common amongst the poor people? After all, they work more physically demanding jobs than the more affluent and consequently their energy expenditure is also higher.
  • How is it possible that a person engaged in heavy physical labor and eating significantly less than 2000 kcals/day may grow obese?
  • How come in fattening experiments where two people eat e.g. 1000 kcals/day more than they need to maintain their weight, for weeks on end, one barely adds a pound of fat while the other puts on nearly ten (note: this alone indicates that there is something else involved than simply caloric balance)?
  • Why do the fat stay fat and the lean stay lean, when obesity research shows that both groups of people are eating on average the same amount of food?


In the second part of the series I will focus on explaining more in detail what happens inside our bodies, how our cells use energy, how fat stores are mobilized, and why the key to unlock this mystery lies in a hormone called insulin.

The urge to simplify a complex scientific situation so that physicians can apply it and their patients and the public embrace it has taken precedence over the scientific obligation of presenting the evidence with relentless honesty. The result is an enormous enterprise dedicated in theory to determining the relationship between diet, obesity, and disease, while dedicated in practice to convincing everyone involved, and the lay public, most of all, that the answers are already known and always have been – an enterprise, in other words, that purports to be a science and yet functions like a religion.

– Gary Taubes, Good Calories, Bad Calories

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