In the nutrition blogosphere, perhaps no phrase is more incendiary than “a calorie is a calorie.” It’s become a pithy way of encapsulating the popular notion that the problem of obesity is nothing more than the consumption of excess energy, or eating too much. When the phrase is used in the context of online micturition contests and forum trolling, it is often done in an effort to provoke those who advocate a low carb or ancestral style diet as a means of losing weight. More specifically, it is usually intended as a rebuttal to the “carbohydrate hypothesis”, a mechanistic explanation for obesity championed perhaps most vociferously by Gary Taubes, author of Good Calories, Bad Calories. The hypothesis, which Taubes lays out in the book, is that consumption of refined carbohydrates leads to hormonal dysregulation at the level of the adipose tissue, ultimately leading to excess fat accumulation (i.e. obesity).
As Taubes himself readily admits, this remains a hypothesis, and as such is still unproven, though he believes at this point it is well supported by the available evidence. He also argues that, if the carbohydrate hypothesis is correct, focusing on the number of calories eaten is less important than the “context” in which those calories are consumed (context here meaning the putative effects of differing macronutrient ratios on fat accumulation). This is sometimes misinterpreted as him believing that “calories don’t matter” or that he’s “denying thermodynamics.” But for those who advocate an ancestral style diet for preventing obesity, this focus on the carbohydrate hypothesis completely misses the point. And attacking it as a means of discrediting the ancestral view of obesity ends up creating a false debate, as it focuses on the problem at the wrong level of analysis (and, for many, is also a straw man, since plenty of folks in the ancestral health community are skeptical of the cho hypothesis).
Much of this rhetorical wheel spinning seems to stem from the fact that, in most ancestral style diets, calories are not counted, leading critics to assert that those advocating this way of eating believe that “calories don’t matter.” The same accusation has been launched ad nauseum at Taubes, typically arising out of a misunderstanding of his views on the misapplication of the laws of thermodynamics. For what it’s worth, Taubes doesn’t argue that calories don’t matter, but rather that the energy balance equation works in both directions — focusing on inputs only ignores half of it. Yet, whether or not Taubes explanation for obesity turns out to be right or not has no bearing on whether an ancestral style diet is the right approach towards maintaining a healthy amount of fat tissue.
In light of this confusion, I think it’s worthwhile to clarify the ancestral view towards body fat regulation and how calorie counting fits into that framework, at least as I see it.
1. Accumulation of excess body fat is fundamentally a problem of disordered homeostasis.
The zillions of biochemical reactions that support a working human being only unfold properly within a narrow range of internal conditions (body temperature, pH, mineral concentrations, etc.). While the external environment of a human may vary considerably, our internal environment cannot. Homeostasis is the process by which the body maintains this vital internal equilibrium.
The central coordinator of homeostasis is the hypothalamus, a tiny, almond-sized structure nestled deep in the brain. Through its position at the helm of the endocrine and autonomic nervous nervous systems and its widespread connections throughout the brain, it can manipulate virtually every aspect of our physiology and behavior on various timescales, all in the service of maintaining homeostasis.
Included within the body’s homeostatic responsibilities is the maintenance of a stable supply of energy, of which the regulation of the fat mass (a large repository of energy) plays an important role. The accumulation of detrimental excessive body fat can thus be viewed as a disorder of energy homeostasis (as could the accumulation of excess sodium or the inability to clear glucose effectively from the bloodstream).
2. Animals can maintain homeostasis most easily in environments in which their species has been adapting to the longest.
The mechanisms that support homeostasis have evolved in and have been shaped by particular environments, and as such are optimized to operate within an expected range of environmental conditions (i.e. ambient temperature, energy availability, day/night cycles, etc.). The greater the mismatch between present conditions and the conditions under which a species is adapted to, the greater the homeostatic challenge. An ostrich can maintain a stable body temperature in the African savannah because, as a species, ostriches have been living in this climate for a very long time. On the other hand, for an ostrich, maintaining temperature homeostasis in Antarctica would present a formidable homeostatic challenge, to say the least.
3. Maintaining homeostasis in evolutionarily discordant environments requires technological adaptations.
In evolutionarily discordant environments (i.e. those that differ considerably from the environment of one’s evolutionary ancestors), endogenous homeostatic mechanisms will likely be insufficient to maintain stable internal conditions. Maintaining homeostasis in these settings will require technological adaptations. Continuing with the example of body temperature regulation, the endogenous homeostatic mechanisms of a human alone are insufficient for survival in an Alaskan winter. Surviving these conditions requires technological adaptations such as fire, clothing, man-made shelter and insulation, indoor heating, etc.
Technological adaptation is what has allowed our species to inhabit and thrive in evolutionarily discordant environments. Unlike the rest of the animal kingdom who cannot live outside the bounds of their homeostatic capabilities, many of us live outside of our species’ “ecological niche” – thanks to technology.
4. When humans eat an evolutionarily concordant diet, technological adaptation is not required to maintain body fat homeostasis.
Just as with other domains of homeostasis, our endogenous mechanisms for body fat regulation are calibrated to the nutritional environments of our hominid ancestors. Thus, when eating an evolutionarily concordant diet (in the presence of intact mechanisms of energy homeostasis), body fat is easily maintained within a narrow range. In this case, the feelings of hunger and satiety (generated by the hypothalamus) are reliable indicators of the body’s energy needs. Likewise, the more evolutionarily novel a food is (read: twinkies, soda, bread, pasta,…), the greater the likelihood there’ll be a need for technological adaptation to maintain body fat homeostasis. In these instances, our endogenous mechanisms are insufficient, and as such feelings like hunger and satiety, no longer an accurate reflection of the body’s energy needs, are unreliable and misleading.
Calories of course matter, but, like animals in the wild, you need not have any specific knowledge of them to maintain body fat within a healthful range. If you are avoiding evolutionarily novel foods, endogenous, subconscious mechanisms for energy homeostasis are sufficient to prevent excessive accumulation of body fat. As has been said elsewhere, if you are eating an ancestral diet “calories count, but why count them?”
5. Calorie counting is a technological adaptation required to maintain body fat homeostasis in an evolutionarily discordant environment.
As stated, maintaining body fat homeostasis in the setting of an evolutionarily discordant diet requires technological adaptation. In the case of body fat regulation, the most commonly employed technological adaptation is to “count calories.” With this method, foods are burned in a bomb calorimeter to determine their energy content, which is then used as a crude surrogate for the energy they add to the organism when consumed. It is an imperfect solution, but at the present time the best available technology for those who wish to eat evolutionarily discordant foods and not accumulate excess body fat.
And that’s it.
Nowhere in this argument is it stated or implied that the energy content of food is irrelevant. That, of course, would be silly. Rather, the point is that energy intake need not be consciously regulated. As you can see, though, this argument is agnostic with respect to the specific mechanisms that disrupt body fat homeostasis. Whether it’s from subversion of food reward mechanisms by nutrient-poor-hyperpalatable foods, insulin-induced local dysregulation of adipose tissue, some combination of these or as yet undiscovered mechanisms is immaterial. Furthermore, the prescription for how to maintain body fat homeostasis does not rest on any understanding of the specific mechanisms that lead to obesity, only that an evolutionarily concordant diet is the most sensible path to achieving it. The mechanisms by which unhealthful amounts of body fat accumulate in evolutionarily discordant diets is still very much a matter of open debate and research, and, given the complexity of the subject, will likely remains so for quite some time.