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Losing body fat while maintaining muscle mass: The role of training volume

by P. Debraux | 2 August 2022

fat loss, muscle, gain, diet, volume, training, fitness, sport, resistance

In many sports, including resistance training, calorie restriction phases of varying length are regularly used by practitioners to reduce their body mass. The main objective is to reduce body fat, but unfortunately a loss of lean body mass (including the mass of bones, muscles, organs, skin and body fluids) is often observed... During a caloric restriction, it is estimated that with a diet alone, about 24% of the loss would come from lean body mass, while a combination of "diet + exercise" would reduce this share to 11%. Moreover, this loss is associated with a decrease in the basic metabolism (the energy the body needs to function at rest). It is therefore essential to find the best strategies to preserve muscle mass as much as possible while succeeding in reducing fat mass.

The conservation of muscle mass is determined by the dynamic balance between muscle protein synthesis and proteolysis (fragmentation of proteins into amino acids). However, during a caloric restriction, in order to reduce energy expenditure, the body decreases the rate of muscle protein synthesis, which explains the decrease in muscle mass. To stimulate protein synthesis, there are two levers that can be used together: a protein-rich diet and weight training. Although strength training is governed by many variables, training volume is particularly important for gains in muscle mass. The greater the volume, the greater the hypertrophy. However, this relationship would likely follow an inverted U-shaped curve. Knowing that in periods of caloric restriction, training becomes increasingly difficult, what impact will a high training volume have on the conservation of muscle mass?

The Study

To try to answer this question, German and American researchers conducted a meta-analysis of 15 studies, including 129 participants (60 women and 69 men) with an average of 6.02 years of experience in strength training. The protocols had to last at least 4 weeks, a caloric restriction of at least 200 kcal/d was performed, data indicated changes in lean body mass, and a high protein diet was used (≥ 2 g/kg/d). Training volume was measured ideally via total tonnage (reps x sets x load), and if this information was not accessible, then in sets/muscle gr./week or sets/exercise). Volume was considered low at less than 5 sets per muscle group per week, medium between 5 and 9 sets and high at 10 or more sets.

Results & Analyzes

The training protocols lasted from 4 weeks to 8 months. An average caloric restriction of -347 kcal was observed in women and -398 kcal in men. The average protein intake was 3.35 g/kg of lean body mass for women and 3.06 g/kg of lean body mass for men. On average, women lost 4.8 kg of body mass and 7.9% of body fat. Men lost an average of 5.0 kg of body mass and 5.2% of fat mass. The change in lean body mass ranged from -6.6 kg to +1.3 kg.

Eleven of the 15 studies used a concurrent strength and cardiovascular training program. The number of strength training sessions ranged from 1 to 7 weekly sessions.

Only 1 study reported training volume in tonnage. The number of sets per muscle group per week was described by 3 studies. Seven studies reported the number of sets per exercise (1 to 10 sets per exercise). And 4 studies did not correctly determine training volume. Five studies increased volume during the training program, 3 decreased volume, and 1 study reported an increase in volume followed by a decrease in volume in preparation for a bodybuilding competition.

Two of the 7 studies including women and 5 of the 7 studies including men reported losses in lean mass, suggesting an influence of gender on changes in lean mass during a restriction phase. The studies reporting moderate to high volumes, with women, reported maintenance of muscle mass or even an increase in lean mass (+1.03 kg on average). Conversely, studies reporting a decrease in volume observed losses in lean mass (-1.04 kg on average).

In men, on average, the loss of lean mass was 2.81 kg, ranging from -0.5 to -6.6 kg, corresponding to 12 to 54% of the total body mass lost. For the two studies that reported no loss of lean body mass, the training volume was increased over time.

Only 4 studies reported training volume correctly. Therefore, it is difficult to draw a clear conclusion on the subject. However, 3 of these studies had a high training volume (10 to 30 sets per muscle group per week) and reported little or no loss of lean body mass (mainly in women). One study following a bodybuilder's preparation for competition even reported an increase in lean mass as training volume increased.

Based on the data from these studies, it appears that in the caloric restriction phase, it is preferable to increase training volume over time and that on average, women appear to maintain their lean mass better than men.

Concerning women

Of 7 studies including women, 1 study reported maintenance of lean body mass and 3 reported an increase in lean body mass. These studies reported a moderate to high training volume, which could increase during the training program. Conversely, the studies that reported a decrease in training volume observed a loss of lean body mass. On average, these women trained 4 to 6 times per week, 6 to 20 sets per muscle group, and ingested large amounts of protein, which may have helped to sustain the training pace and thus indirectly protect lean mass.

Concerning men

Seven studies included men and 1 study included both women and men. Of these 8 studies, only 2 reported little, no loss or even an increase in muscle mass (measured via muscle cross-sectional area). These studies involved an increase in volume during the training period.

In a case study of a bodybuilder's contest preparation, a marked loss of lean body mass coincided with a marked reduction in calories and a greater volume of cardiovascular training when the athlete reached less than 7% body fat. Once the caloric deficit becomes too great, even an anabolic stimulus such as high volume training seems insufficient to counteract the diet-induced anabolic resistance. Furthermore, if volume follows an inverted U-shaped relationship with hypertrophy, it could be either too little or too much, depending on individual ability.

Compared to women, increased training volume appears to only partially counteract the disruptions induced by caloric restriction without completely reversing them. Although men and women have similar activation of the mTOR signaling pathway, there are differences in body composition, muscle composition, hormones and mitochondrial activity. Women appear to retain lean body mass better during caloric restriction. Some researchers speculate that this may be due to a higher concentration of estrogen which has an anabolic effect on IGF-1.

Possible mechanisms

Caloric restriction induces hormonal changes that can negatively affect the protein balance and therefore contribute to the loss of lean body mass. This is because the body would allocate the available energy to more important physiological processes.

Studies suggest that testosterone plays a role in maintaining lean body mass, and that this relationship is dependent on energy levels. Indeed, some research has shown that a loss of lean body mass under caloric restriction corresponds to a drop in testosterone concentration, while maintaining testosterone levels is accompanied by a maintenance of lean body mass. The drop in testosterone associated with caloric restriction could negatively affect certain signaling pathways and could therefore have a negative effect on protein balance.

Changes in lean body mass are determined by the dynamic balance between muscle protein synthesis and degradation. This ratio is affected by many variables such as available energy and nutrients, growth-related hormones, sleep level and mechanical tension.

The mechanistic target of rapamycin (mTOR) modulates the magnitude and duration of muscle protein synthesis. During a phase of caloric restriction, mTOR activation is reduced, resulting in reduced protein synthesis and increased protein breakdown. Without a reverse stimulus (such as weight training, for example) this leads to a significant loss of lean mass.

Some studies have shown that higher training volumes increase intracellular anabolism when the calories consumed match the calories expended, but this would appear to be the case during caloric restriction phases as well.

Practical Applications

The results presented in this review suggest that reducing training volume during a period of caloric restriction would negatively impact lean mass retention. Although the scientific data are still insufficient, increasing volume seems to be a relevant solution. However, this would also depend on other factors such as the volume of training before the start of caloric restriction, the value of the caloric deficit, the level of fat mass, the use or not of concomitant cardiovascular training and the level of the exerciser (the more trained, the higher volume). In addition, based on the results mentioned in this literature review, women tend to maintain more lean body mass compared to men.

Caloric reduction is generally accompanied by a decrease in hormonal stimuli, which increases catabolism. Maintaining or even increasing training volume could be a successful anti-catabolic strategy thanks to the preservation of a positive protein balance and a hormonal environment conducive to the maintenance of muscle mass.


  1. Roth C, Schoenfeld BJ and Behringer M. Lean mass sparing in resistance-trained athletes during caloric restriction : the role of resistance training volume. Eur J Appl Physiol 122 : 1129-1151, 2022.

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