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Old 05-30-2009, 05:24 AM   #4
Darryl Shaw
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Join Date: Apr 2008
Posts: 708
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Quote:
Originally Posted by Jason Barrow View Post
Totally agree Mike, thanks for your input.

I suppose I'm curious as to what to make of weight loss achieved on a calorie controlled diet like Weightwatchers, when so much information points to it not being a simple calories in-calories out equation?

Or to come at it from an exercise angle, what about weight loss achieved when no change is made to diet but a person goes crazy with the gym sessions? I've got a guy who's convinced the key to his 14lb+ drop in weight was down to his 2hr routine 4x a week! Seems pretty easy to say "well of course, you dramatically increased your calorie expenditure, created a deficit and bingo- weight loss!"

(on a side note, when you guys first starting first starting questioning what you might call the mainstream conceptions of health/fitness.......anybody else feel like their head was going to explode?! )
Sorry but as this extract from Exercise Physiology: Energy, Nutrition and Human Performance by McArdle, Katch & Katch (p.855 - 856) points out it really is as simple as energy-in vs energy-out.

Quote:
The first law of thermodynamics (often called the law of conservation of energy) posists that energy can be transferred from one system to another in many forms but cannot be created or destroyed. In human terms this means that the energy balance dictates that body mass remains constant when caloric intake equals caloric expenditure. Figure 30.15 shows that any chronic imbalance on the energy output or input side of the equation changes body weight.

There are three ways to unbalance the energy equation in order to produce weight loss:

1: Reduce energy intake below daily energy requirements.

2: Maintain caloric intake and increase energy expenditure through additional physical activity above daily energy requirements.

3: Decrease daily caloric intake and increase daily energy expenditure.

When considering the sensitivity if the energy balance equation, if caloric intake exceeds output by only 100 kcal per day the surplus calories consumed in a year equal 36,500 kcal (365 days x 100 kcal), because 0.45kg (1 lb) of body fat contains 3500 kcal (each 1 lb [454g] of adipose tissue contains about 86% fat or 390g x 9 kcal/g = 3514 kcal per lb) this caloric excess causes a yearly gain of 4.7kg (10.3 lb) of body fat. In contrast, if daily food intake decreases by 100 kcal and energy expenditure increases by 100 kcal then the yearly deficit equals the energy in 9.5kg (21 lb) of body fat.

The previous arithmeticic represents an overly simplistic accounting for fat accumulation because the diets composition affects the bodies efficiency in converting and storing excess calories as fat. Only about 3% of ingested lipids are lost when the body converts the calories to stored fat. In contrast 25% of carbohydrate calories "burn" during the conversion. Simply stated, the body synthesizes fat far more efficiently from dietary lipid than from an equivalent excess of carbohydrate. Whether shifting dietary composition toward higher carbohydrate content actually produces less body fat gain with a caloric excess remains unresolved.
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