What does protein do to the body
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The Role of Protein in the Body
Protein and Body Composition
Muscle Accretion and Fat Loss
Protein plays a crucial role in enhancing body composition, particularly in individuals who engage in regular exercise. Increased dietary protein intake, above the recommended dietary allowance (RDA) of 0.8 g/kg/day, has been shown to promote muscle accretion and fat loss. This effect is particularly pronounced when combined with exercise, as protein helps in muscle repair and growth while also aiding in fat reduction 29.
Lean Mass Retention
During weight loss, higher protein intake is beneficial for retaining lean body mass. Studies have demonstrated that older adults and athletes who consume higher protein diets (≥25% of energy intake or approximately 2.3 g/kg/day) retain more lean mass and lose more fat mass compared to those on lower protein diets 810. This is crucial for maintaining muscle strength and overall metabolic health during periods of caloric restriction.
Protein and Metabolic Health
Insulin Sensitivity
Moderate to high protein intake has been associated with improvements in insulin sensitivity. Overweight and obese individuals who consume diets with 25-40% of energy from protein, combined with exercise, show significant improvements in insulin sensitivity and reductions in body fat percentage . This suggests that protein can play a role in managing and potentially preventing insulin resistance and type 2 diabetes.
Satiety and Thermogenesis
Protein is more satiating than carbohydrates and fats, which helps in regulating food intake and body weight. The increased satiety from protein is partly due to diet-induced thermogenesis, where the body expends more energy to digest and metabolize protein compared to other macronutrients 45. This thermogenic effect contributes to a higher energy expenditure, aiding in weight management and reducing the likelihood of weight regain after weight loss.
Protein and Cardiovascular Health
Lipid Profile
High-protein diets can positively influence lipid profiles. For instance, individuals on high-protein diets often experience reductions in total cholesterol and triglycerides, which are beneficial for cardiovascular health. Additionally, moderate protein intake has been shown to elicit similar benefits in body composition and metabolic profiles as high-protein diets, without the potential adverse effects associated with very high protein consumption .
Practical Implications
Dietary Recommendations
Given the benefits of protein on body composition, metabolic health, and satiety, increasing the percentage of energy intake from protein while reducing overall energy intake can be a practical strategy for weight management. This approach is particularly effective under ad-libitum energy intake conditions, where individuals can eat freely but are more likely to consume fewer calories due to the satiating effect of protein 46.
Special Populations
Certain populations, such as individuals with prediabetes or those without obesity risk alleles, may benefit more from high-protein diets. These groups have shown greater improvements in body weight management and metabolic health when consuming diets rich in protein .
Conclusion
Protein is a vital macronutrient that significantly impacts body composition, metabolic health, and satiety. Higher protein intake, especially when combined with exercise, promotes muscle growth, fat loss, and improved insulin sensitivity. It also enhances satiety and thermogenesis, aiding in effective weight management. Therefore, incorporating adequate protein into the diet is essential for overall health and well-being.
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