Proteins and Body Weight
Professor, Nutritional Sciences and Physiology; Director, Program in Food Safety, Nutrition and Regulatory Affairs, Department of Nutritional Sciences, Faculty of Medicine, University of Toronto
The role of protein in the regulation of long-term energy balance and maintenance of healthy body weight remains unclear. Nonetheless, high-protein diets remain popular due to perceived benefits such as increased satiety. Evidence is mounting that the source of protein is very important in this regard.
The role of dairy products
Dairy products and/or dairy components have been shown to suppress short-term food intake, increase subjective satiety and stimulate the mechanisms known to signal satiation and satiety.1 Calcium may also play a role in body weight regulation.2 However, several studies indicate that calcium supplements have a less significant effect than dairy calcium, suggesting that components in milk other than calcium may be at work.2 Dairy proteins are much higher than meat or plant proteins in the branched chain amino acids (BCAA), especially leucine, a proposed benefit to food intake regulation and the maintenance of lean body mass.3
Benefits of high-quality protein
Research indicates four lines of evidence supporting a role for proteins in the regulation of food intake and the maintenance of healthy body weight.3 Briefly:
- Protein suppresses food intake more than fat or carbohydrate
- Protein promotes satiety and delays the return of hunger compared with fat and carbohydrate
- Energy-restricted diets high in protein support the maintenance of lean body mass, thereby promoting weight loss primarily as adipose tissue
- Protein digestion leads to the stimulation of many physiological and metabolic responses known to be involved in food intake regulation.
A variety of studies demonstrate that protein source is a factor.3,4 For example, rat studies show that food intake suppression in the next hour of feeding is greater following gavage with whey compared with egg-albumin and soy protein.5 The two principal proteins in milk, casein and whey, each contribute to satiety.4 Casein, being more slowly digested contributes to longer-term satiety while whey contributes to shorter-term satiety.4 In addition, peptides and other bioactive components found in milk products appear to confer a number of benefits including modulation of blood pressure, inflammatory processes and control of blood glucose levels.4 Unfortunately, the majority of Canadians fail to meet their daily requirement of milk products.6
- A growing body of evidence supports a role for dairy products in the regulation of body weight.
- Calcium supplements do not appear to confer the same benefit as dairy calcium, suggesting that other components in milk may be a factor.
- Proteins in milk, including casein and whey, improve satiety, regulate food intake and promote the maintenance of lean muscle mass.
- Peptides and other bioactive components in milk products appear to have additional benefits including modulation of blood pressure, inflammation and blood glucose levels.
- Aziz A and Anderson GH. The effect of dairy components on food intake and satiety: mechanisms of actions and implications for the development of functional foods. In Saarela M (ed): “Functional Dairy Products.” Cambridge, UK: Woodhead Publishing Ltd, vol. 2, 2007.
- Major GC et al. Recent developments in calcium-related obesity research. Obesity Reviews 2008;9:428-445.
- Anderson GH and Moore SE. Dietary proteins in the regulation of food intake and body weight in humans. J Nutr 2004;134:974S-979S.
- Luhovy BL et al. Whey proteins in the regulation of food intake and satiety. J Am Coll Nutr 2007;26(6):704S-712S.
- Morgan G. The role of cholecystokininA-receptors in protein hydrolysate-induced suppression of food intake in rats. In: Department of Nutritional Sciences, Toronto, Ontario: University of Toronto; 1998:143.
- Statistics Canada. Nutrition: findings from the Canadian Community Health Survey 2004. Overview of Canadians' eating habits. Ottawa, Canada: Health Statistics Division, 2006:47.