ZT
Energetics of Weight Loss
Weight loss occurs when the body's composition is being changed in a different way than in weight gain. Due to lack of food, bodily components are oxidized for energy and the body shrinks. During weight loss the caloric value of fat does not change when compared to carbohydrate. Under these physiological conditions, all food stuffs have their correct and computed energy content.
Weight loss has long been regarded as a simple reduction of the fat content of the body. It must be recognized, however, that changes in body composition taking place during periods of deficient caloric intake are more complex than simple loss of fat.
Usually we estimate weight loss by assuming that one pound of adipose tissue, which is about 85% fat, contains 3,500 calories. Thus, if we eat 7,000 calories less per week, we would lose two pounds. In reality, in the beginning of a weight loss period, we lose four pounds the first week. This is because carbohydrate, protein and water will be mobilized as well as fat. The caloric value of tissue lost during the first week is about 1,700 calories/lb of body tissue loss (7,000 calories divided by 4) instead of 3,500 calories per pound of fat tissue.
As weight reduction continues, however, the situation changes. Now, mostly fat will be burned and the predicted loss of weight will reflect the caloric value of a pound of adipose tissue. For each 3,500 calories less consumed, one pound of fat will be lost. Unfortunately, the body eventually adapts to this new situation and reduces its energy expenditure. Generally, during weight loss, metabolic rate goes down by about 25%, even though the person tries to maintain the same energy requiring activities.
Energetics of Weight Loss
Weight loss occurs when the body's composition is being changed in a different way than in weight gain. Due to lack of food, bodily components are oxidized for energy and the body shrinks. During weight loss the caloric value of fat does not change when compared to carbohydrate. Under these physiological conditions, all food stuffs have their correct and computed energy content.
Weight loss has long been regarded as a simple reduction of the fat content of the body. It must be recognized, however, that changes in body composition taking place during periods of deficient caloric intake are more complex than simple loss of fat.
Usually we estimate weight loss by assuming that one pound of adipose tissue, which is about 85% fat, contains 3,500 calories. Thus, if we eat 7,000 calories less per week, we would lose two pounds. In reality, in the beginning of a weight loss period, we lose four pounds the first week. This is because carbohydrate, protein and water will be mobilized as well as fat. The caloric value of tissue lost during the first week is about 1,700 calories/lb of body tissue loss (7,000 calories divided by 4) instead of 3,500 calories per pound of fat tissue.
As weight reduction continues, however, the situation changes. Now, mostly fat will be burned and the predicted loss of weight will reflect the caloric value of a pound of adipose tissue. For each 3,500 calories less consumed, one pound of fat will be lost. Unfortunately, the body eventually adapts to this new situation and reduces its energy expenditure. Generally, during weight loss, metabolic rate goes down by about 25%, even though the person tries to maintain the same energy requiring activities.
