Minimum Volume During Fat Loss Phases
How much do we need to train during fat loss phases?
Low body fat levels are advantageous for athletes that need to improve power to body mass rations, their health, or make weight for competition. Fat loss phases will be necessary: eating less energy, measured in calories, than needed to force the body to burn body fat for energy. The human body is in a constant state of protein synthesis (production) and protein breakdown (Table 1). Calorie restriction is one of many factors that increases protein breakdown (Table 2), and if this exceeds protein synthesis, this can result in muscle loss, leading to reductions in strength, power and performance.
Table 1: Relationship between protein synthesis and breakdown on muscle hypertrophy and atrophy
Table 2: Factors influencing protein synthesis and breakdown
Resistance training is one of the key methods of preventing muscle loss by increasing protein synthesis and reducing protein breakdown. In fat loss phases recovery is impaired and muscle growth difficult/impossible for advanced lifters, so it is useful to know the maintenance volume or minimum dose to maintain muscle during fat loss phases.
Muscle retention, or even gains, is more likely with moderate calorie deficits (below 500kcal), high protein diets (1.7-2.2g per kg bodyweight) (Bandegan et al., 2017), adequate sleep (Song et al., 2023), carbohydrates (Noakes et al., 2006) and without excessive endurance training (Wilson et al., 2012) or over-extended fat loss phases (Cava et al., 2017). I will assume that these variables are controlled, otherwise training will be less effective and greater volumes will be required for muscle maintenance (Israetel & Hoffman, 2019).
The stimulus for muscle growth or maintenance is similar with heavy or light weights (between 30% and 85% 1RM). All high threshold motor units, and therefore muscle fibres that they activate, will be active for the final few repetitions, as long as the target muscles are the limiting factor and we push all sets close to failure (Schoenfeld et al., 2017). The magnitude of the stimulus is dictated by time under tension which can be measured by the number of stimulating reps and can be further estimated from the number of sets performed close to failure (Schoenfeld et al. 2017). Baz-Valle et al., (2021) confirmed that the total number of sets is a valid measure of the hypertrophy stimulus.
There is a wide range of individual responses to training while in a calorie deficit, with some being high responders, gaining/maintaining muscle easily, and low responders (Riberio et al., 2019). A meta analysis by Murphy & Koehler (2021) found that some people were better at maintaining muscle in a calorie deficit, some were even able to gain muscle. This may be due to environmental (sleep), individual factors (genetics, training experience), or perhaps some are following the plan better than others! Females seem to maintain their muscle mass better than males, potentially because males generally have more muscle mass to lose (Roth et al. 2021). Assuming nutrition and recovery is equal, low responders will likely need more stimulus than high responders to maintain muscle during fat loss phases. Therefore the amount of sets should be tailored to the individual, by evaluating their previous response to different training volumes.
We know that training volume follows a dose-response relationship with hypertrophy (muscle building). This means that the more sets an individual performs, the greater the stimulus, the more likely they are to retain muscle. Research has found that individuals with training experience can get stronger with just 2/3 sets per week, or 3-6 sets for powerlifters (Androulakis-Korakakis et al., 2020; Androulakis-Korakakis et al., 2021). However it is possible to gain strength without gaining muscle, or even while losing muscle, so it is likely that the minimum dose to maintain muscle is greater than 2 sets per week.
The minimum dose to stimulate hypertrophy is around 4 sets per week, according to meta-analyses by Robinson et al. (2024), Schoenfeld et al. (2017) and Pelland et al. (2024), with each additional set improving hypertrophy by about 0.24 and 0.36%. At higher volumes additional sets provide diminishing returns, although very high volumes of up to 52 sets have been found to lead to greater muscle gain (Enes et al., 2024).
We need to stimulate enough protein synthesis to exceed protein breakdown for hypertrophy to occur (recall Table 1). To maintain muscle, we only need to stimulate enough protein synthesis to balance protein breakdown. Therefore less volume is needed to maintain muscle than to build it. However a calorie deficit reduces protein synthesis and increases protein breakdown (Table 2), so in fat loss phases we likely need more volume to maintain muscle.
Moving on to studies that have directly measured muscle retention during calorie restriction, two studies have reported that 12 weekly sets was enough to gain muscle in a calorie deficit (Donnely et al. 1993; Garthe et al., 2011). This indicates that less than 12 sets per week are required to maintain muscle. Roth et al. (2022) found no difference in muscle retention between 6 and 12 sets per week, indicating that the minimum effective dose may be 6 set or less per week. Finally Carlsen et al. (2022) found 5 weekly sets, with additional forced reps assisted by the coach, was enough to maintain muscle during fat loss phases.
Based on the evidence, I estimate that we need to perform approximately 4 to 6 sets per muscle group to maintain muscle during fat loss phases, when the target muscles are taken close to failure. However, this can be scaled up or down, depending on the training history of the individual. Lifters are advised to experiment and find their minimum effective volume landmarks, the amount of volume required during hypertrophy phases, which can be used to estimate maintenance volume during fat loss phases, It is advisable to perform more than the minimum dose to reduce the chances of undershooting and losing muscle. The safest method to avoid muscle loss during fat loss phases is not to drop volume and continue to perform similar amount of sets as hypertrophy phases.
A final note is that is may be advisable to increase the amount of weekly sets over the course of the fat loss phase. This is because muscle breakdown increases over the duration of fat loss phases, requiring greater training stimulus to balance out protein synthesis. This is supported by studies that show better muscle retention when volume is increased, and more muscle loss when volume is constant (Roth et al. 2022).
I hope you have found this article interesting and can use the information to help you maintain, or even gain muscle during your next fat loss phase.
Patrick
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