Obesity From First Principles
Life can only be sustained so long as certain internal conditions are met and maintained over long periods. Life, in this context, means more than mere survival. It includes the vitality and agency of a healthy organism that allows it to deal successfully with its environment. Sickness is a failure to maintain homeostasis in some dimension important for life.
Body composition is one such dimension. Fat stores satisfy energetic demands between meals, particularly during times of scarcity where meals are small or infrequent. From an athletic perspective, however, fat tissue is pure deadweight which slows us down and increases wear and tear. Given this trade-off, some optimal level of fatness must exist for every organism and species.
We should therefore expect the successful organism to be self-regulating with regard to its body composition. It is too important for life to leave up to chance and circumstance. Any study of obesity must therefore try to explain the factors that cause the organism to reach a different level of fatness than what is optimal from a body composition-only perspective.
Broadly speaking, two classes of reasons are possible: Either the homeostatic control of body composition has become dysfunctional and the organism has lost the ability to self-regulate it, or optimal body composition is being sacrificed to achieve homeostasis in some other dimension deemed more important for health.
In recent years, it has been popular among the fat acceptance movement to blame obesity on genetics, an explanation that tends to belong to the first category. A common assumption is that the human body never had the ability to self-regulate body composition and achieved leanness historically only via the discipline imposed by an energetically scarce environment.
This view fails at the get go, since most of the world has abundant food, and yet obesity still hits only a minority of people—though a rapidly growing one. For most people, casual observation makes obvious that their bodyweight must be regulated. Otherwise, how can their energetic intake match their expenditure to a point where bodyweight fluctuates by a mere few kg each year? This cannot be due to external circumstances.
We therefore turn to the alternative explanation. That is: Since body composition is not the only bodily dimension that must maintain homeostasis for optimal health, obesity could be a side effect of a drive towards homeostasis in some other dimension more important for life under conditions that do not allow the organism to simultaneously achieve its body composition goals.
Since obesity is intimately linked with an excess intake of energy from food, and since feeding serves also the function of providing those nutrients required for health that do not relate to energy supply directly, a plausible hypothesis is that obesity results from a drive to achieve nutritional adequacy in a nutrient deficient environment.
That is, if the diet is deficient in essential nutrients (protein, vitamins, minerals, essential fatty acids) but rich in energy (carbohydrates and fat), the organism may not be able to satisfy its nutritional needs while maintaining energy balance and may therefore sacrifice the latter to achieve the former.
Since the detriments to health and life of excess body fat is likely to be smaller than that of nutrient deficiency, this seems a worthwhile trade-off. Excess body fat reduces mobility in the short run and contributes to chronic diseases in the long run, but nutrient deficiency threatens to undercut basic bodily functions on any time frame. Life is impossible without nutrition. It is merely more difficult with excess body fat.
So the cure for obesity should really be quite simple: Select foods with an adequate ratio of essential nutrients to energy. Importantly, this requires no self-limitation on the quantities eaten on the part of the person dealing with obesity, since our premise is that the body self-regulates as long as it is provided with the right conditions for doing so. That is, we should expect appetite to automatically regulate to a level that brings body composition into its optimal range.
For now, we have dealt with essential nutrients only in the abstract. But to operationalize this strategy, it is necessary to identify which essential nutrients are likely to drive hunger when inadequately provided, and which foods provide them in sufficient quantities. We will address this question in another post.