Building muscle traditionally requires an energy surplus, meaning consuming more calories than the body burns daily. However, recent evidence confirms that muscle mass can be built while eating at maintenance calories, a process known as body recomposition. Maintenance calories refer to your Total Daily Energy Expenditure (TDEE), the number of calories required to keep your body weight stable. Body recomposition is the simultaneous gain of muscle tissue and loss of body fat, resulting in a net change in body composition with little or no change in scale weight. This method offers a sustainable alternative for those who wish to avoid excess fat gain associated with the classic “bulking and cutting” cycle.
The Mechanism of Energy Partitioning
The ability to gain muscle without a caloric surplus hinges on a metabolic process called nutrient partitioning. Nutrient partitioning describes how the body decides where to allocate incoming calories—to be used immediately for energy, stored as fat, or directed toward tissue repair and synthesis, such as muscle growth. When calories are consumed at maintenance, the body needs an additional energy source to fuel the energetically expensive process of muscle protein synthesis. This is where stored body fat becomes a functional energy reserve.
The body accesses chemical energy stored within adipose tissue, creating an internal calorie deficit without changing total food intake. This mobilized fat energy supplies the “surplus” required for muscle growth, while ingested calories, especially protein, provide the necessary building blocks.
Resistance training significantly improves nutrient partitioning, making muscle cells more sensitive to nutrients than fat cells. The mechanical stress from lifting weights creates a demand signal, encouraging the body to shuttle nutrients preferentially toward damaged muscle fibers for repair and growth.
Factors Determining Success
The feasibility and speed of building muscle at maintenance are highly dependent on an individual’s starting point and training history. Individuals who are new to resistance training, often referred to as “newbies,” are the most primed for successful body recomposition. Their muscles are highly sensitive to the new training stimulus, leading to a robust and prolonged spike in muscle protein synthesis that facilitates rapid gains, a phenomenon known as “newbie gains.”
An individual’s current body fat percentage is also a major factor. Higher body fat levels provide a larger, more accessible energy reserve, allowing individuals to sustain body recomposition with greater ease and for a longer duration.
In contrast, an advanced lifter with a low body fat percentage will find the process significantly slower and more difficult. Their bodies have a reduced pool of available fat energy to mobilize, and their muscles are less sensitive to the training stimulus compared to a beginner. For very lean, highly trained individuals, a slight caloric surplus may become necessary to maximize the rate of muscle gain.
Optimizing Protein and Training Stimulus
Achieving body recomposition at maintenance calories requires deliberate optimization of both diet and training.
Dietary Optimization
The most important dietary input is a high intake of protein, which supplies the amino acids necessary to build new muscle tissue. A protein intake of approximately 0.8 to 1.0 grams per pound of body weight (or 1.6 to 2.2 grams per kilogram) is commonly recommended for maximizing muscle growth in combination with resistance training. Distributing this protein intake relatively evenly across three to five meals per day can help sustain the muscle-building process throughout the day. While protein is paramount, carbohydrates and fats still serve important functions, with carbohydrates helping to replenish muscle glycogen stores to fuel intense workouts and aid recovery.
Progressive Overload
The training component must provide a strong signal for muscle adaptation, which is accomplished through progressive overload. Progressive overload means consistently increasing the demand placed on the muscles over time, such as by lifting heavier weights, performing more repetitions, or increasing the total volume of work.