Obesity has been increasing with an unprecedented rate in the United States and the rest of the world. There are approximately 65% overweight people in the U.S. and about 33% are clinically obese. This trend is also rising among children and teens. Due to the other health issues related with excess body weight, such as high cholesterol, high blood pressure, diabetes, and cardio-vascular diseases, obesity is perceived as an epidemic.
In the recent years, there has been a significant discussion about the effect of high proteins foods on weight loss. The first person to suggest this correlation was Dr. Atkins through his Atkins diet program. This started a series of marketing campaigns by the food industry promoting their high protein foods. These marketing nudges seem to have brought a misconception among the common public that any food high in proteins would help to lose weight. This article highlights the importance of protein nutrition for general health and well being along with its role in weight regulation.
A good protein intake is required for optimum heath as our muscles, which constitute about 40-50% of the human body mass, are mostly composed of proteins. Proteins are made of amino acids, which therefore are building blocks for the human body. The amino acids supplied from dietary protein are needed for synthesis of body proteins in muscle, organs, bone and skin, and for synthesis of enzymes, certain hormones, antibodies and a host of specialized products. Certain amino acids are essential for proper functioning of the body and the brain, such as tryptophan found in corn. In addition, proteins are essential as various specific proteins produced as a result of gene expression carry out all general functioning of the body. That is, the genetic pool of the human body that is composed of DNA and its associated genes gives rise to specific proteins that carry out their individual functions. Deficiencies of protein or one or more of the essential amino acids leads to reduced growth in children or loss of muscle mass in adults.
A diet high in proteins has been related to weight loss and weight maintenance in various recent studies. Protein keeps the body satisfied for a longer time, the feeling of satiety. There is convincing evidence that a higher protein intake increases thermogenesis (the process of burning fat to produce body heat) and satiety as compared to diets of lower protein content. The weight of evidence also suggests that high protein meals lead to a reduced subsequent energy intake. Some evidence also suggests that diets higher in proteins result in increased weight loss and fat loss as compared to diets lower in protein. (1).
Protein plays a key role in food intake regulation through satiety related to diet-induced thermogenesis. Protein also plays a key role in body weight regulation through its effect on thermogenesis and body composition. A high percentage of energy from dietary protein limits body weight (re)gain through its satiety and energy inefficiency related to the change in body composition. (2)
Fairly recently, Dr. Frank Hu at the Harvard School of Public Health, Boston, Massachusetts published a review on the effects of high protein diets on weight loss (1). Followings are the key points of this review:
o Although authors of some fad diets have advocated increasing dietary protein for weight loss, not until recently have studies begun to investigate the effects of high protein diets on weight loss.
o Convincing evidence exists that protein exerts an increased thermic effect when compared to fat and carbohydrate. Evidence is also convincing that higher protein diets increase satiety when compared to lower protein diets.
o Higher protein diets may facilitate weight loss when compared to a lower protein diet in the short term (within 6 months). But long-term data are limited.
o Exchange of protein for carbohydrates has been shown to improve blood lipids, and in epidemiologic studies, higher protein diets have been associated with lower blood pressure and reduced risk of coronary heart disease.
o Although the optimal amount and sources of protein cannot be determined at this time, the weight of evidence suggests that in dietary practice, it may be beneficial to partially replace refined carbohydrate with protein sources that are low in saturated fat.
In summary, a good protein nutrition is essential for body muscle mass and essential amino acids. In addition, high protein intake seems to have an effect on weight loss and weigh maintenance due to its effect on satiety and thermogenesis. However, a careful selection of the protein foods should be made, as the high-protein foods are also generally high in fat, for example red meat such as beef and pork. If the diet has to be modified by including high-protein foods, the selection criteria should include plant-protein food sources, such as soy, beans, pulses, as they are generally low in fat. The good sources of animal proteins are fish and chicken as they are in general low in saturated fat and high in unsaturated fats, such as omega-3 fatty acids.
1. Halton H. and Hu F. (2004) The Effects of High Protein Diets on Thermogenesis,
Satiety and Weight Loss: A Critical Review. Journal of the American College of Nutrition, Vol. 23(5):373-385.
2. Westerterp-Plantenga MS (2003) The significance of protein in food intake and body weight regulation. Curr Opin Clin Nutr Metab Care. Vol. 6(6):635-8.