Weight Loss, Diet and Fitness Program

One of the first things they teach in basic nutrition class is that calorie balance– calories in versus calories out– determines if you gain or lose weight. You will gain body fat if you consume more calories in the diet that you expend through metabolism and exercise and lose fat if caloric expenditure exceeds caloric intake.

Several well-controlled studies showed that people lose more weight on an Atkins-type low-carb diet than low-fat or mixed diets. Could it be that all calories are not the same?
Nutrition researchers from the University of Wisconsin, Madison, pointed out that proteins have less available energy (energy after digestion) than do fats or carbohydrates. Burning protein in a bomb calorimeter (measures the energy contained in foods) renders 5.65 calories while available calories after absorption is only 4.0 calories. Values for fats are 9.4 and 8.9 calories and carbohydrates are 4.1 and 4.0, respectively. You lose nearly 30 percent of the energy from protein, but only seven percent from fat and two percent from carbs.

This only accounts for about half the weight loss differences between subjects on high- and low-carb diets. Every gram of glycogen (stored carbohydrate) is stored with three grams of water.
Low-carb diets deplete the muscles and liver of glycogen, which releases water and causes weight loss/fat loss. Low-carb diets are effective in the short-term; scientist do not completely understand why.