Maintaining muscle mass during an energy deficit: the importance of protein

Whether for health, aesthetic, or performance reasons, many people undergo periods of calorie restriction (also called a “hypocaloric diet”) to lose weight. However, we must be aware that weight should not, by any means, be the focus of attention, since the goal should always be an improvement in body composition (that is, promoting fat loss without having negative effects on muscle mass).

If a period of caloric restriction is maintained for a very long time or if such caloric restriction is of great magnitude, we run the risk of losing muscle mass. Muscle mass is the balance between protein synthesis and protein degradation, and in situations of low energy consumption, the body will reduce protein synthesis and increase protein degradation as a way of obtaining energy. Something similar can occur, for example, in endurance athletes subjected to heavy training loads (e.g., ultra-endurance). Due to their high energy expenditure, if nutrient intake does not meet the requirements of these athletes, their body will increase protein degradation as a way of obtaining energy, thus resulting in a loss of muscle mass. But what can we do to prevent it?

Proteins to prevent muscle mass loss

Increasing evidence shows that during periods of calorie restriction it is possible to increase or at least maintain muscle mass. That said, to achieve this we should maintain stimuli that increase protein synthesis, such as strength training and, especially, protein intake. This is why during calorie restriction it is essential to maintain a high protein intake. Confirming these benefits, a study conducted in young people who trained intensely (6 days a week) analyzed the effects of a hypocaloric diet (40% calorie restriction) for 4 weeks.¹ During this study, some subjects consumed a high-protein diet (2.4 g/kg/day) while others consumed half the protein (1.2 g/kg/day). After 4 weeks, both groups had improved their performance and lost body fat, although the group with higher protein intake lost a greater amount of fat (-4.8 kg versus -3.5 kg).¹ In addition, only the group that had consumed more protein managed to increase their muscle mass (+1.2 kg versus 0.1 kg).

Similar results to those mentioned above in young people and athletes have also been observed in overweight individuals. For example, in people with obesity who followed a hypocaloric diet for 13 weeks, increasing protein intake (1.11 g/kg/day instead of 0.85 g/kg) through the consumption of a supplement managed to prevent the loss of muscle mass that did occur in the group consuming less protein (+0.4 and -0.5 kg change in muscle mass, respectively), without causing differences in fat loss (-3.2 and -2.5 kg on average).² In addition, we must not forget that proteins also have other additional benefits that can promote weight loss, such as their high satiety power and a greater thermogenic effect.³

Conclusions and recommendations

Although low-calorie diets will always produce weight loss, the important thing should be to improve body composition. During periods of severe calorie restriction, it is possible that part of the weight lost is due to a loss of muscle mass, which can have negative consequences for health and performance. Increasing protein intake is essential to prevent this loss of muscle mass, and it can even increase fat mass loss. Thus, if the general protein recommendations (0.8 g/kg) are already insufficient for practically the entire population, especially in athletes, in the case of people following a low-calorie diet it has been proposed that protein intake should be substantially increased to reach values close to 1.6-2.4 g/kg, being higherprotein consumption the greater the caloric restriction.⁴

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References

1. Longland TM, Oikawa SY, Mitchell CJ, DeVries MC, Phillips SM. Higher compared with lower dietary protein during an energy deficit combined with intense exercise promotes greater lean mass gain and fat mass loss: A randomized trial. Am J Clin Nutr. 2016;103(3):738–746.
2. Verreijen AM, Verlaan S, Engberink MF, Swinkels S, Vogel-Van Den Bosch J De, Weijs PJM. A high whey protein-, leucine-, and vitamin D-enriched supplement preserves muscle mass during intentional weight loss in obese older adults: A double-blind randomized controlled trial. Am J Clin Nutr. 2015;101(2):279–286.
3. Valenzuela PL, Castillo‐garcía A, Lucia A, Naclerio F. Effects of combining a ketogenic diet with resistance training on body composition, strength, and mechanical power in trained individuals: A narrative review. Nutrients. 2021;13(9).
4. Phillips SM. A Brief Review of Higher Dietary Protein Diets in Weight Loss: A Focus on Athletes. Sport Med. 2014;44(Suppl 2):149–153.