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Posted by on May 30, 2014 in Nutrition, Food | 0 comments

Body Fat Setpoint Theory

Body Fat Setpoint Theory

One pound of human fat is about 3,500 calories. If you were to increase or cut 115 calories (1 lrg apple, 1 toast, 1.5 slice of cheese, etc.) from your daily diet you would respectively gain or lose a pound in a month (115 x 30= 3500). Right?…not quite. I’ve tried it and it doesn’t work, and most of you will agree with me.
How is it that most people’s body fat stays relatively stable over a long period of time? Doesn’t the body know how to use a calculator? We eat less, bust ass in the gym and the number on the scale remains the same. To soften the blow, you will be told that you’re gaining muscles, which is a lot more dense than fat. You reluctantly accept, even though it doesn’t seem like it.
Here is what’s going on:
The body is a sophisticated system operating on a delicate interplay of hormones and neurons, constantly striving for homeostasis. To maintain equilibrium, energy intake is stacked up against expenditure to ensure a healthy fat mass.

Food intake <—-> satiety/energy expenditure in the form of heat production/physical activity

In a properly functioning system, if you ate more than usual at a meal, you will eat less the next time and even burn off the extra as heat.
In a study published in American Society for Clinical Nutrition [1], researchers overfed lean and modestly overweight volunteers 50% more calories than they normally consumed, under controlled conditions with the macronutrient ratio of 12-42-46 % protein-fat-carbohydrate.

After 6 weeks, both lean and overweight subjects gained an average of 10 lb of fat mass and 6.6 lb of lean mass. Also, metabolism and body heat of the subjects increased, as if their bodies were trying to burn off excess calories and return to baseline.

Following this, subjects were allowed to eat however much they wanted for 6 weeks. Both lean and overweight volunteers lost 6.2 of the 10 lb they had gained in fat (61% of fat gained), and 1.5 of the 6.6 lb they had gained in lean muscle mass (23%). Here is a graph showing changes in fat mass for each individual:grafThe subjects were followed for only 6 weeks after overfeeding, so it is not known if they lost the remaining fat mass in the following weeks. But, it appears that they were reaching a plateau slightly above their original body weight. So we can say, nearly all subjects “guarded” their original body fat mass and maybe more.
What is interesting is that underfeeding studies have shown the same phenomenon: whether lean or overweight, people tend to return to their original fat mass after underfeeding is over. These studies support the hypothesis that the body has a fat mass “set point” that it likes to protect against changes in either direction, and that’s the mere definition of homeostasis.
Now the question is:
With such a system in place to keep body fat mass in a narrow range, why do we get fat at all?
It is postulated that obesity and major departure from body’s set point occurs when the system malfunctions. The network that used to defend a low fat mass is now defending a high fat mass, and we end up eating more. So band aiding the situation with “eat less and move more” advice, which may work temporarily, is not very realistic. An ideal solution digs deep and attempts to work with the underlying physiological state. This is why low-calorie diets, and most diets in general, typically fail in the long term, since most people find it miserable to fight hunger every day.
Now the question is:

  1. What caused the system to defend a higher fat mass?
  2. Is it possible to modify the setpoint?

[1] Metabolic response to experimental overfeeding in lean and overweight healthy volunteers.

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