Holland Clinic

Protein:

Protein is the macronutrient whose calories are most lost during digestion and
metabolism. One might conclude on this basis that an obvious approach to
weight control is therefore to increase dietary protein intake and to a limited
degree this is likely true, but too much dietary protein is unhealthy and can
cause kidney damage.

How much protein is too much?

The answer depends upon a person's health. Some bodybuilders claim to
consume three hundred grams of protein daily without problems, but generally,
protein intake in excess of 150 grams per day is likely too much and for people
suffering from kidney disease, far less than this warranted. The actual amounts
needed by women and men average about 46 and 56 grams respectively.

What all this means is that one can utilize the high thermic effect of protein to
help weight loss, but only to a limited degree.

Alcohol:

Alcohol has a relatively high thermic effect, but this is largely counteracted by
stimulation of appetite so that it makes no sense to use alcohol as part of a
weight-control plan. Furthermore, as is widely known, alcohol is dangerous to
human health when consumed in excess.

Carbohydrate:

Compared to protein, carbohydrate has a low thermic effect, but, it is still
between about two and five times better than fat. This, combined with
carbohydrate's relatively low caloric density of 4 kcal/gram, means that in fact,
carbohydrate should be the main calorie source in a weight loss diet.

Why?

Because carbohydrate has none of the kidney damaging potential of protein,
because it is highly palatable and, as mentioned is not calorie dense. This
subject is discussed in far greater detail elswhere herein.

Fat:

Very little dietary fat is lost as heat during digestion and metabolism. This, along
with fat's very high calorie density makes it the macronutrient to be most
carefully limited by people attempting weight loss.

Conclusion:

Not all calories are equal. Some are more efficiently "absorbed" than others, and
this fact can be used to a limited extent to assist people in designing a diet for
weight control, but the potential toxicity of the most thermic macronutrient,
protein, limits the extent to which manipulation of caloric effiency is practical.