SCIENTIFIC THINKING ABOUT WEIGHT CONTROL

Posted: May 8th, 2009 | Author: admin | Filed under: Weight Loss | No Comments »

Fat balance: The physiological model

The next development examined the separate nutrient balance equations, i.e. fat, alcohol, carbohydrate and protein equations. In human physiology it became clear that fat imbalance was the main cause of energy imbalance. Hence the formula to describe this became the following:

Rate of change of fat stores = rate of fat intake — rate of fat oxidation.

This developed from important physiological studies in the 1980s which found that in humans, fat stores come largely from dietary fat, and that under most conditions, fat balance equals energy balance. It is only under unusual conditions that humans convert significant amounts of non-fat calories into fat for storage. This model then suggests fat imbalance as the primary cause of an imbalance between energy intake and utilisation. Hence, the approach is a major step forward because it moves away from regarding obesity as a pathological state in a ‘normal’ environment. Because the problem of obesity is so widespread in modem societies, it suggests that the opposite is almost certainly true, i.e. that the spectrum of body sizes from lean to obese represents the normal variations of physiology and, within a ‘pathological’ environment (which favours obesity), many more are at the obese end of the spectrum. However, there are still problems with this approach. The fat balance equation above describes the changes in fat stores that occur within a given individual over time. It is less clear how differences in body fat between individuals arise. Why is it that some people remain relatively lean when they seem to have the same sort of lifestyle as others who are overfat? It also fails to explain the differences in obesity prevalence between populations. To explain this requires an expanded approach.

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