Why Are We Overweight? Part 8
In earlier installments, I explained how modern man has undergone lifestyle changes that render our inherent system of body fat regulation ineffective for keeping our energy-balance ledger in check. Basically, a hormonal system exists that rewards behavior that would be required when a negative energy balance is in effect (i.e., when the calories we expend exceed those we consume) and this makes sense because that set of circumstances threatens our existence. The take-home message is that when we need energy, we derive reward from activity because we should have to hunt to get our food. Conversely, when a positive energy balance prevails, we are not inclined to be active, but this is okay because we also won’t derive reward from eating. This means that if this system was the only one guiding our behavior, we would simply lie around and satisfy the energetic cost of living when we were operating in the black until enough energy had been used to establish the negative balance once again.
In modern man, the growing overweight epidemic suggests that the homeostatic system described above is being supplanted. A likely explanation is that another reward circuit based upon energy intake for reasons other than necessity is playing a role in dictating our actions. For example, we are now inclined to eat according to our circadian clock and we also place a high priority on the palatability of the foods we ingest. Furthermore, establishing the appropriate energy balance is the last thing driving us when we eat for social purposes or to counter stress. Finally, we even drink energy now, which further confounds a system designed exclusively for zero-calorie liquid (i.e., water). The end result is that it’s easy to wind up ingesting more than you need and once you do, the vicious cycle perpetuated by reduced physical activity begins.
To exemplify the difference between how things should be and how things are, I have previously cited the behavior of animals in the wild. Generally speaking, within a given species, wild animals look pretty much the same; that is, they carry an amount of body fat that is typical for animals of their kind. Sure, elephants carry more fat than tigers, but that’s simply a matter of how their species has evolved. The key thing is that all elephants are virtually the same, which supports the notion that homeostatic control is driving their behavior. And this is not surprising when you consider what the act of eating does (and, perhaps more importantly, does not) entail for these animals.
Coupled with changes in how we procure food (the calories expended pushing your cart up and down the aisles at the supermarket pales in comparison to what the tiger uses when he chases down the deer), the dramatic alteration in what energy ingestion represents to modern man means that you cannot trust your instincts when figuring out how much to eat and how active to be. Instead, you have to use your brain. The first step is determining the amount of calories you need to maintain your current level of body fat. This is called your caloric maintenance level and is critical to know because once you figure out what you require to stay the same, you can adjust the value based upon how you want to change. And in addition to providing information regarding how much to eat, knowledge of this value also allows you to establish the proper nutrient balance for your diet.
Foods are comprised of protein, carbohydrates and fats, which are macronutrients that are needed for many different functions within the body. The reference daily intake (RDA) values for these macronutrients have been established and are expressed relative to the total amount of calories you consume. For example, it’s recommended that 10-35 percent of your total energy intake comes from protein sources, 45-65 percent from carbohydrates and 20-35 percent from fats. Generally speaking, one gram of protein and one gram of carbohydrate are each metabolized to provide four calories of energy, while fat is a more dense source that yields nine. Consequently, if you know your caloric maintenance level, you can perform simple arithmetic calculations to figure out how much protein, carbohydrate and fat you need.
It is not unusual to find formulas that are purported to provide estimates of caloric maintenance level. For example, if you Google “calculate calorie needs,” you’ll find no less than 83,700 hits! Typically, these calculators require that you enter your gender, age, weight and height, along with a vague estimate of how physically active you are. From this information, your caloric maintenance level is predicted. Unfortunately, it is rarely this simple. There is tremendous inter-individual variability with respect to how much energy we need simply to stay alive (i.e., our basal metabolic requirement) and on top of this, describing activity level with a blanket term to estimate the energy you’ll expend above basal is fraught with imprecision. The bottom line is that for broad-brush purposes, a prediction formula might suffice, but if you want to devote the appropriate amount of attention to determining this critical value that modern man must know, there’s a better way.
This article was originally published in New Living Magazine, which can be accessed on-line at www.newliving.com.
