Saturday, January 29, 2011

The Nutrition Debate #6: “Energy In = Energy Out”: An Alternative Interpretation

The one universally held truth in our understanding of human metabolism is the Energy Equation: Energy In = Energy Out. It is accepted by most doctors, even some medical researchers, and universally by the popular press and the entire general public. Why? Because it is so easy to understand, and it’s just plain good “common sense.”

It also gains gravitas by its association with one of the basic laws of science, the First Law of Thermodynamics, paraphrased here just a bit: “the net (energy) supplied to the system equals the net work done by the system.” Who can argue with that? You’d have to be some kooky doctor or maverick scientist to even try, and you would be laughed at all the way to (and in) the grave (viz: Atkins).

Okay. I’m crazy enough to try. I get the courage because Gary Taubes, in his seminal opus “Good Calories – Bad Calories” introduced in the last installment, makes the argument convincingly for me. So, with apologies to him for any errors in my understanding, I will attempt to regurgitate his explanation here to help convey his Alternative Interpretation of this immutable law of thermodynamics, as applied to the Energy In = Energy Out formulation for weight control.

The problem with the conventional interpretation of the Energy In = Energy Out formula is that it measures “energy in” and “energy out” in the wrong place, i. e., exclusively outside the body, as something done to the body. Thus, the common-sense, universally accepted understanding is as follows: Energy In (food ingested) = Energy Out (basal metabolism plus the added energy expenditure of activities, including exercise). Therefore, to lose weight (“improve” the energy balance) you must restrict calories (i.e., reduce “energy in”) and exercise more (increase energy expended, i.e., “energy out”). Sound familiar? Of course! It’s the ubiquitous “diet and exercise” prescription. This interpretation of how the Energy Equation works, that is, where to measure “energy in” and “energy out,” is fundamentally wrong. Here’s why.

According to Taubes, the operative place to observe and measure homeostasis (how the body itself modifies energy intake and expenditure to maintain a balanced state), is in the blood stream. There, “Energy In” is the sum of the products of digestion and absorption (of nutrients from foods eaten), plus “quick” energy from food previously eaten, digested and stored (primarily as glycogen in the liver and muscles), and lipolysis, the breakdown and then oxidation (burning) of the body’s own fat cells. Thus, the source of our energy in the blood stream (the “energy in” or left side of the equation) is basically three-fold: 1) the small intestine (where digested food is absorbed into the blood stream), 2) stored carbohydrate energy (glycogen) available to the blood stream from the liver and muscles, and 3) our adipose tissue (fat cells, or triglyceride molecules), which, if allowed to break down, can move into the blood stream and contribute to “energy in.” Particularly take note of this last additional source on the “energy in” side of the equation, and the very important conditional aspect of it.

Thus, the body balances the equation itself, through complex signals from various hormones, putting on the right side of the equation however much energy it needs for our basal metabolism plus what our activity level requires. It uses the first two sources on the left side of the equation (food eaten and carbs stored), and then, providing it is “free” to take it, energy from the third source: it uses our fat cells for energy. This last energy source, however, is conditional and absolutely critical. This source of “energy in” is the critical difference that 1) avoids the starvation diet aspect of conventional restricted calorie but balanced diet programs, 2) prevents that always hungry feeling, including cravings and the need for between meal snacks, 3) gives the body all the energy it needs, avoiding that drained, and weak feeling that people get from balanced, starvation diets. It is also an easy way to lose weight (body fat) and keep it off, if you stay with it, for life.

When understood from this perspective, and with some additional insights from our knowledge of the macronutrient components of the foods we eat, and the key role of the hormone insulin, we can gain an understanding of how to use all three sources on the “Energy In” side of the equation to meet our body’s total requirements for “Energy Out.” In the next installment we’ll discuss what “free to use it” means, and how the mechanism works.

© Dan Brown 1/9/11

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