High-Protein Diet May Increase Thermogenesis

The Durk Pearson & Sandy Shaw®
Life Extension NewsTM
Volume 7 No. 1 • February 2004

High-Protein Diet May Increase Thermogenesis Compared to High-Carbohydrate Diet

Although there have been several studies suggesting greater weight loss from a high-protein, low-fat diet compared to a high-carbohydrate, low-fat diet, the mechanisms remain undetermined. One small recent study1 (10 healthy, normal-weight, nonsmoking women aged 19–22 years) suggests that postprandial (after-meal) thermogenesis is increased, averaging about 2-fold higher at 2.5 hours postmeal, after the high-protein, low fat-meal as compared to the high-carbohydrate, low-fat meal.

In a randomized trial cited in the paper, 65 healthy, overweight, and obese subjects consumed ad libitum (as much as they wanted) a high-protein test diet containing 24% of energy from protein and 29% of energy from fat. The high-carbohydrate diet contained 59% energy from carbohydrate and 29% energy from fat. After 3 months, the subjects consuming the high-protein diet lost more weight (7.5 kg) compared to subjects consuming the high-carbohydrate diet (5.0 kg). After 6 months, the weight loss was 8.7 kg vs. 5.0 kg, respectively; 35% of the high-protein-diet subjects lost greater than 10 kg of weight, whereas only 9% of the high-carbohydrate-consuming subjects did so.

The authors note that the thermic response to protein ingestion is 50% to 100% higher than that for carbohydrate, which is generally attributed to the additional energy costs of metabolizing proteins in, for example, breaking peptide bonds and gluconeogenesis. Moreover, others had reported that following protein consumption, postprandial REE (resting energy expenditure) rises rapidly and is sustained for as long as 4 to 5 hours. Carbohydrate consumption, by contrast, induces REE more modestly, and REE falls rapidly 1 to 2 hours after the meal. The purpose of their study was to determine, with commonly eaten foods and meal plans, the metabolic cost of a high-protein, low-fat diet versus the “currently recommended” high-carbohydrate, low-fat diet. The authors conclude that “Increased diet-induced thermogenesis, in association with the preservation of REE [resting energy expenditure], may contribute to the reported weight-loss success of diets high in protein with moderate levels of carbohydrate and lends credence to the observation that weight loss on high-protein diets is predominantly body fat, not body water.”

One interesting point made by some researchers cited in the paper is that thermogenesis is increased more by more palatable food. They use, as an example, that a palatable meal of Parmesan fondue, spaghetti and meatballs, and a chocolate clair increased diet-induced thermogenesis 50% more than if the same meal ingredients were blended, desiccated, and consumed as a tasteless biscuit! This would suggest that, all other things being equal, if you want to increase thermogenesis, it may not help to eat tasteless food. (But you will have to avoid overeating delicious foods, too! Note that the example is loaded with carbohydrate . . .)

This is interesting information on the thermogenic effects of a high-protein versus high-carbohydrate diet. Still, it is a very small study (10 subjects), and the subjects were very young (19–22 years). We hope there will be more and larger studies of this kind that include middle-aged subjects.

  1. Johnston et al. Postprandial thermogenesis is increased 100% on a high-protein, low-fat diet versus a high-carbohydrate, low-fat diet in healthy, young women. J Am Coll Nutr 21(1):55-61 (2002).

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