Protein values ​​of up to 4.0 g/kg body weight are common in weight training and bodybuilding. Such massive amounts have never been based on research, nor are they recommended in reputable sources.

Depending on the source and various studies, protein intake amounts of 1.4-3.3 g/kg body weight are given for people of normal weight who want to build muscle mass. Sports science institutions usually recommend a protein intake of 1.3-1.8 g/kg body weight for adults who train intensively [1] . With intakes of more than 2.6 g/kg body weight, no additional muscle growth was detected, but fat gain could be reduced with a high-calorie diet (mass phase/bulking) [2][3] .

If, for certain reasons, the total energy intake is reduced (calorie deficit), a proportionally increased protein intake of 1.8-2.7 g/kg body weight is recommended (see also "Definition & Diet" or "Weight reduction").

[1] Hot Topic Protein in Sport Version 3.1 , ed. by Swiss Sports Nutrition Society

[2] Leaf A, Antonio J. The Effects of Overfeeding on Body Composition: The Role of Macronutrient Composition - A Narrative Review . Int J Exerc Sci . (2017)

[3] Antonio J, et al. A high protein diet (3.4 g/kg/d) combined with a heavy resistance training program improves body composition in healthy trained men and women--a follow-up investigation . J Int Soc Sports Nutr . (2015)

Proteins are also used by the body as a source of energy when the overall energy balance is negative. Therefore, a proportional increase in protein intake is particularly important in this situation. If the energy intake is low, slightly higher amounts of 1.8-2.7 g protein per kg body weight are recommended. Dietary proteins affect satiety and body composition. Ingesting protein fills you up more than equal amounts of energy from carbohydrates or fat and requires more energy to digest, which means fewer net calories. In addition, the fat-free body mass (muscle mass) is better preserved with a simultaneous decrease in body fat. [1] [2]

[1] Proteins in the human diet (2011) , ed. by Federal Nutrition Commission, May 2011

[2] Hot Topic Protein in Sport Version 3.1 , ed. by Swiss Sports Nutrition Society

Increasing the protein intake in weight-reduction diets is important because the body uses proteins as a source of energy when the overall energy intake is insufficient (calorie deficit). People with a vegetarian or vegan diet must take special care to ensure that their requirement for essential amino acids, which cannot be produced by the body itself, is met. Ingesting protein fills you up more than equal amounts of energy from carbohydrates or fat and requires more energy to digest, which means fewer net calories. In addition, the fat-free body mass (muscle mass) is better preserved with a simultaneous decrease in body fat. [1]

A protein quantity of 1.8-2.7 g/kg body weight is recommended for people who are physically active in order to lose weight (calorie deficit) [2] .

For overweight or obese people who do not exercise, 1.2-1.5 g/kg body weight per day is recommended as protein intake if there is no impairment of kidney function [1] .

[1] Proteins in the human diet (2011) , ed. by Federal Nutrition Commission, May 2011

[2] Hot Topic Protein in Sport Version 3.1 , ed. by Swiss Sports Nutrition Society

Protein not only supports muscle building, but also maintenance and regeneration of the muscles after exertion, which is often neglected by endurance athletes in particular. The protein requirement is strongly dependent on the daily amount of sport and the intensity. On the other hand, a breakdown by sport makes little sense. Whether muscle building or endurance is trained is only of limited importance. Rather, it is about supporting specific training phases and goals. Accordingly, there is now a uniform, sport-independent recommendation for protein intake. For adults, this is 1.3-1.8 g/kg body weight per day [1] .

[1] Hot Topic Protein in Sport Version 3.1 , ed. by Swiss Sports Nutrition Society

Adequate protein intake and energy intake is of great importance in older people, as this population group has an increased risk of diseases and malnutrition. If illness, injury or being bedridden are added to this, sufficient protein intake becomes all the more important. With a view to bone health in old age, in particular the avoidance of bone fractures, a protein intake of 1.2 g/kg body weight per day is recommended for older people - with an adequate energy intake (!) - to prevent the breakdown of body protein and muscles. In the case of serious, muscle-wasting illnesses with a balanced energy balance, even 1.2-1.5 g/kg body weight and day are recommended. Sporting activity increases the protein requirement accordingly to 1.3-1.8 g/kg body weight. If the energy intake is low due to illness or other reasons (e.g. loss of appetite), a proportionally increased protein intake is also all the more important. [1]

For older people and those suffering from wasting illnesses, it is particularly important that slightly larger portions of protein are consumed per intake, namely 25-30 g [2].

[1] Proteins in the human diet (2011) , ed. by Federal Nutrition Commission, May 2011

[2] https://www.ncbi.nlm.nih.gov/pubmed/19057193