Proteins and weigh control
Protein is one of the major nutrients in our food and they are the building blocks of every cell of our body. Some of their functions are widely known: they contribute to the growth and maintenance of muscle mass, they are needed for building and repairing body tissues, and they function as enzymes and hormones and contribute to the normal function of the immune system (Duyff R. 2012). But proteins have another key role in nutrition; they could be helpful for the maintenance of body weight.
Observational studies have shown that higher-protein diets are associated with lower BMI (Body Mass Index) and waist circumference (Pasiakos, 2015). What is more, scientific evidence shows that low calorie high protein diets are more effective than low calorie standard protein diets when it comes to weigh loss and fat mass reduction as well as maintenance of fat free mass (Falcone et al., 2015; Leidy et al., 2015; Pasiakos, 2015; Pasiakos et al., 2015a; Pesta and Samuel, 2014; Wycherley, 2012; Flechtner-Mors, Boehm, Wittmann, Thoma, & Ditschuneit, 2010; Layman et al., 2009; Lee et al., 2009).
Moreover, studies have shown that after initial weight loss, high protein diets could be more likely to help keeping the weight from coming back, therefore improving weigh maintenance (Aller et al., 2014; Leidy et al., 2015).
Some of the possible mechanisms for explaining these effects are increased satiety and diet induced thermogenesis, and the maintenance of muscle mass that comes with high protein diets.
Several studies have shown that protein help us feeling fuller and satisfied for a longer period of time than carbohydrates and fats (St. Jeor et al., 2001, Paddon-Jones et al, 2008; Leidy et al., 2015; Dhillon, 2016) mainly due to the influence of protein consumption on appetite and satiety regulating hormones (Blom et al., 2006; Bowen, Noakes, & Clifton, 2006; Bowen, Noakes, Trenerry, & Clifton, 2006; Weigle, 2005; Belza et al,. 2013,Yang D et al. 2014).
But the effect of proteins on satiety not only can be seen by the higher and long lasting feeling of fullness that follows the consumption of high protein foods, but also by the higher induction of satiety in high protein diets (Westerterp-Plantenga, et al. 2009; Yang D et al. 2014), which would end up in reduced caloric intake. As some studies have shown, high protein diets could lead to a calorie intake reduction of up to 440 Kcal per day (Weigle, 2005).
Additionally, high protein diets have shown to have a greater effect in reducing the desire to eat late at night and the preoccupation with thoughts of food than standard protein diets, which could be of aid for reducing evening overeating and late-night snacking (Leidy, 2011).
Increased Diet Induced Thermogenesis
Diet Induced Thermogenesis, also known as Thermic Effect of Food, is the amount of energy needed to digest, absorb, and metabolize nutrients and stands for around 10% of the total daily energy expenditure. Is influenced by the energy density and macronutrient composition of a meal. Protein generates a greater termic effect of food than carbohydrates or fats, in fact, the termic effect of proteins is up to ten times higher than in fats, and three times higher than in carbohydrates (Leidy, 2015). This means that the body burns more calories when processing proteins than processing fats or carbohydrates.
The influence of muscle mass
Muscle burns three times more calories per day than body fat, in fact each kilogram of muscle burns about 14Kcal per day, while fat only 4.5 Kcal per day (Butte, 2014), therefore, maintaining (or increasing) muscle mass, is key to promote energy expenditure throughout the day. But, when one undergoes a weight loss diet, one of the main challenges is to induce a loss of fat mass while maintaining lean muscle mass. Several studies have shown that, while inducing more weigh and fat mass loss, high protein diets are also helpful for maintain muscle mass (Wycherley et al., 2012).
In addition to exercising, one of the major stimuli for muscle building is the appropriate protein intake. But when it comes to muscle building, not only the total amount of protein consumption matters; the quality, timing and distribution of protein during the span of the day matter as well. For better muscle stimuli, 20 to 30 g of high quality protein should be consumed per meal. (Esmarck et al., 2001; Mosoni and Mirand, 2003; Hoffman, 2007; Candow and Chilibeck, 2008; Paddon-Jones and Rasmussen, 2009; Layman, 2009; Symons et al., 2009; English and Paddon-Jones, 2010; Stark et al., 2012; Adechian et al., 2012; Moore et al., 2012; Bauer et al., 2013; Deutz and Wolfe, 2013; Bouillanne et al., 2013; Ivy and Schoenfeld, 2014; Helms et al., 2014; Mamerow et al., 2014; Margolis and Rivas, 2015; Perez-Schindler et al., 2015). Besides, results from numerous studies indicate that an even distribution of total daily protein intake (e.g., 30 g/meal) is more beneficial than skewed amounts of protein intake (e.g., 10 g for breakfast, 20 g for lunch, and 60 g for dinner) throughout the day in promoting muscle building (Moore et al., 2012; Mamerow et al., 2014).
Nevertheless, in spite of what science has shown, the usual protein intake distribution of adults is typically skewed, with a low intake at breakfast, which does not reach the threshold of 20–30 g, and unnecessarily exceeding it at dinner (Paddon-Jones et al. 2015).
Sources and examples
Benefits of protein on appetite and weigh control have been shown to be similar no matter if the protein comes from animal or vegetal source (Neacsu, 2014). Therefore, the recommended food sources of protein are lean meats, protein, fish, low-fat dairy, eggs, soy and other legumes, and protein supplements.
 BMI is a measure that uses your height and weight to assess if your weight is within healthy parameters