How To Achieve Concurrent Fat Loss and Muscle Gain: A Scientific Perspective



The notion of simultaneous fat loss and muscle gain has traditionally been met with skepticism, often considered attainable only by distinct demographic sub-groups such as novices to resistance training, obese individuals, or those using performance-enhancing drugs. However, a more nuanced understanding of physiology and metabolism reveals that this phenomenon, known as body recomposition, is possible for a broader range of individuals. Despite some arguments premised on the laws of thermodynamics, recent findings suggest that fat loss and muscle gain can indeed coexist.

The Thermodynamics Argument: A Reassessment

The argument against concurrent fat loss and muscle gain generally revolves around three points:

  1. Muscle building requires energy storage, whereas fat loss necessitates energy expenditure.
  2. An energy surplus leads to energy storage, whereas an energy deficit results in energy loss.
  3. Thus, one must be in an energy surplus to gain muscle and in a deficit to lose fat.

While the first two assertions are grounded in the energy conservation law, the third represents a misconception. Muscle and fat are distinct functional compartments within the human organism. The body can independently allocate caloric intake towards muscle and fat mass through calorie partitioning. It is conceivable to build muscle while in a caloric deficit, as the body may derive the necessary energy from stored fat reserves.

Empirical Evidence: The Isola et al. 2023 Study

In a recent study by Isola et al. (2023), researchers examined how dieting impacts body composition, resting energy expenditure (REE), and hormone levels in physique athletes. Among the salient findings were:

  • Both male and female athletes lost fat mass during the dieting phase.
  • Interestingly, some individuals demonstrated gains in muscle cross-sectional area and lean body mass.

This empirical research underscores the feasibility of achieving concurrent muscle gain and fat loss, albeit with some stipulations regarding the population studied and the methodologies employed.

A Framework for Concurrent Fat Loss and Muscle Gain

Achieving body recomposition requires a meticulous approach, encompassing energy balance, macronutrient ratios, and exercise regimens.

Energy Balance

  • A mild or moderate caloric deficit of between -500 and -300 kcal is recommended.

Macronutrient Distribution

  • Protein intake should be between 2.6-3.5 g per kg of Fat-Free Mass (FFM).
  • Fats should comprise 0.5-1.0 g per kg of body weight.
  • The remaining caloric intake should be sourced from carbohydrates, preferably consumed around workout times.

Resistance and Cardiovascular Training

  • Resistance training should be undertaken at least three times per week, with a focus on tracking progression.
  • Adequate aerobic fitness is crucial for tolerating intense workouts and facilitating fat metabolism.

Other Factors

  • Optimize time around resistance training to maximize anabolic effects.
  • Prioritize quality sleep and overall recovery strategies.

Limitations and Recommendations

Achieving body recomposition is not advisable for individuals leading hectic lives, requiring meticulous planning and execution. Future research could also explore individual differences in the ability to achieve body recomposition, taking into account genetic factors and long-term sustainability.


In light of the scientific evidence, it is prudent to reassess traditional viewpoints that decry the possibility of concurrent muscle gain and fat loss. While challenges exist, a scientifically informed approach can guide individuals in achieving this ambitious but attainable goal.