Increase Percentage of Protein Intake to Improve Body Composition
As the summer season approaches, many people will become more interested in losing weight and improving their body composition. Increasing protein consumption, compared to other macronutrients, while decreasing total caloric intake, may be a viable strategy to help people decrease their body weight and improve their body composition. Paddon-Jones, Westman, Mattes, Astrup, and Westerterp-Plantenga (2008), highlight three main reasons moderately increasing protein intake may facilitate such changes; protein improves satiety, protein increases thermogenesis, protein helps maintain and create fat-free mass.
First protein is different than both fats and carbohydrates. Proteins are composed of amino acids that perform a wide range of functions in the body, such as maintaining structure of skeletal muscle, acting as hormonal messengers, helping catalyze reactions, working as antibodies,, helping regulate DNA, and many others (Becker & Smith, 2006). Basically, proteins form the building material for important substances. Unlike the other macronutrients, the body does not store protein and protein’s main function is not to provide energy. Due to its limited storage capability and poor ability to be utilized as an energy source, protein should not form the majority of a person’s caloric intake.
Satiety is the feeling of fullness one feels after eating. Protein rich foods increase satiety more than carbohydrate rich foods or high fat foods. High protein meals increase satiety through decreasing gherlin concentrations, a hormone produced in the stomach which helps regulate hunger, and stimulates the hormone CCK, which signals fullness (Paddock-Jones et al., 2008). This improved satiety should decrease a person’s excess food consumption. In a study of three breakfast compositions (high protein, high carbohydrates, and high fat) among 30 adult men, Fallaize, Wilson, Gray, Morgan, and Griffin (2012) found that the group who had the high protein meal for breakfast consumed less calories during breakfast and dinner, when compared to the other groups. High protein meals may lessen caloric intake by increasing satiety.
Protein is also more thermogenic than the other macronutrients. Foods high in protein have higher levels of energy expenditure in digestion, absorption, transport, and metabolism. Protein increases diet induced thermogenesis by 15-30% over baseline resting metabolic rate compared to carbohydrates (5-10%) and fats (~3%) (Pesta & Samuel, 2014). Meals high in protein basically need more energy to digest compared to meals with different macronutrient composition.
Increased protein intake helps preserve lean body mass during weight loss when combined with exercise. The maintenance of muscle mass in a hypocaloric state is attributed to increased amino acid levels, particularly leucine, which stimulates the initiation of translation and increases protein synthesis, preventing the net loss of muscle protein (Mettler, Mitchell, & Tipton, 2010). Mettler and colleagues examined whether subjects eating a diet high in protein (35% of energy) would maintain muscle mass compared to a low protein diet (15%) over 2 weeks. Although the group eating the low protein diet lost slightly more weight, they lost a significantly greater amount of lean muscle mass than the high protein group (1.5 kg compared to 0.2 kg on average). Protein helps preserve lean mass during weight loss.
Based on the evidence, protein should be increased slightly. The average person consumes around 15-16% of their energy supply from protein. It should be increased to around 20-25% at the expense of either fats or carbohydrates, depending on training status. If an athlete cuts back on their carbohydrate to increase their protein intake, increased contribution of amino acids to energy expenditure with an equal decrease in lipogenesis due to decreased supply of dietary glucose, which likely negatively impacts exercise performance and training intensity (Pesta & Samuel, 2014). An athlete should cut their fat intake, when increasing their protein if looking to lose weight. Conversely, an obese nonathlete would be advised to cut carbohydrates as dietary carbohydrates might impair fat oxidation and a reduction in carbohydrates would reduce adipose tissue development. While diet planning should be done with a registered dietician, but if one follows the recommendations of Pesta and Samuel of 20% protein, 50% carbohydrate, and 30% fat, a person should successfully be able to lose weight without sacrificing appetite or lean muscle mass.
Becker, G. W., & Smith, K. (2006). Basic metabolism III: Protein. Surgery (Oxford), 24(4), 115-120.
Fallaize, R., Wilson, L., Gray, J., Morgan, L. M., & Griffin, B. A. (2012). Variation in the effects of three different breakfast meals on subjective satiety and subsequent intake of energy at lunch and evening meal. European Journal of Nutrition, 52(4), 1353-1359.
Mettler, S., Mitchell, N., & Tipton, K. D. (2010). Increased protein intake reduces lean body mass loss during weight loss in athletes. Medicine & Science in Sports & Exercise, 42(2), 326-337.
Paddon-Jones, D., Westman, E., Mattes, R. D., Astrup, A., & Westerterp-Plantenga, M. (2008). Protein, weight management, and satiety. American Journal of Clinical Nutrition, 87(5), 1558-1561.
Pesta, D. H., & Samuel, V. T. (2014). A high-protein diet for reducing body fat: Mechanisms and possible caveats. Nutrition & Metabolism, 11(1), 53-71.