Why Calories Still Matter

Over the past decade or so, alternative explanations for the rise in obesity rates, that de-emphasize the role of caloric intake vs. the role of specific nutrients, have had a field day.  

Leading amongst these, no doubt, is the Carbohydrate-Insulin-Model (CIM) of obesity, whereby, carbs stimulate insulin release, which in turn stimulates expansion of adipose tissue, which in turn leads to insulin resistance, resulting in even higher insulin levels, ultimately resulting in a vicious cycle that can only be interrupted by religious adherence to a low-carb diet. 

Although this model has had broad populistic appeal, spawning a whole industry of best-sellers, low-carb products, and even treatment programs built around this paradigm, as pointed out in rather comprehensive article by Kevin Hall and a host of notable obesity experts, published in the American Journal of Nutrition, CIM (which has undergone several modifications since its inception), does not quite concur with all of the pre-clinical and clinical evidence. 

In this paper, the authors make a rather compelling argument in favor of the Energy-Balance-Model (EBM), which pretty much aligns with virtually everything we know about the science of body weight regulation. 

According to the authors,

“The EBM proposes that the brain is the primary organ responsible for body weight regulation via integration of external signals from the food environment along with internal signals from peripheral organs to control food intake. Specific brain regions, such as the hypothalamus, basal ganglia, and the brainstem modulate food intake below our conscious awareness via complex endocrine, metabolic, and nervous system signals acting in response to the body’s dynamic energy needs as well as environmental influences…..whereas day-to-day energy intake and energy balance of an individual can be highly variable, neural regulation of energy balance is generally achieved over prolonged time scales.”  

The key term in all of this is “positive energy balance”, without which there can be no accumulation of excess weight. Ergo, as calories are  the currency of energy balance, there can be no excess energy balance without excess calories. 

As the authors go on to explain, the physiological processes that determine caloric intake are subject to a host of biological and environmental perturbations, explaining both the differences in individual susceptibility as well as the wide variability in shape and size evident even in populations with similar environmental exposure. Furthermore, this model also explains the wide variation in response  to dietary, pharmacological, or even surgical manipulations that modify the functioning of the system. 

Importantly, while the EBM model of obesity fully accommodates a role for high-glycemic foods and a role for insulin, it also allows for a number of alternative mechanisms that ultimately drive positive energy balance. 

Recognizing the central role of caloric intake, does not mean that we all need to go back to calorie counting or restrictive caloric dieting – rather, it is clear that such approaches tend not to be very effective in the long-term and may in fact be counterproductive in terms of obesity management. 

However, turning to simplistic alternative notions that disregard the fundamental importance of caloric balance is neither helpful nor in line with the basic laws of physics that govern conservation of energy. 

Or, as the authors highlight,

…the CIM sets forth a single exposure as the primary determinant of common obesity and proposes a single “practical strategy” to treat obesity by prescribing low-glycemic-load diets despite evidence that such interventions are no more effective than prescribing higher-glycemic-load alternatives.“

As a general rule, when faced with simple explanations or solutions to a complex problem, a certain level of skepticism is generally in order.

Berlin, D