For decades, the fitness community has operated under a strict and seemingly inescapable binary. If you wanted to build muscle, you had to embark on a “bulk,” accepting the inevitable accumulation of body fat in pursuit of maximum hypertrophy. If you wanted to get lean, you had to enter a “cut,” bracing yourself for the frustrating stagnation or even regression of your strength and muscle mass. The concept of body recomposition—simultaneously gaining muscle while shedding fat—has long been treated as a fitness unicorn. Conventional wisdom among experienced lifters dictates that “recomping” is something reserved exclusively for complete beginners or individuals utilizing performance-enhancing substances. Once an athlete has spent a few years under the barbell, the argument goes, that metabolic window slams shut, forcing them to forever alternate between distinct phases of gaining and losing weight.
However, a closer look at scientific literature reveals that human physiology is far more nuanced than gym lore suggests. As researchers dig deeper into the energetics of resistance training and metabolism, the rigid lines separating bulking from cutting are beginning to blur, offering a more flexible perspective for intermediate and advanced lifters alike.
To understand why body recomposition has been so heavily scrutinized, it helps to examine the prevailing body of research comparing caloric surpluses to maintenance energy levels. Several scientific studies over the years have sought to determine how manipulating caloric intake impacts individuals undergoing structured resistance training. Generally speaking, these studies have found that operating within a caloric surplus produces similar or slightly greater gains in measured muscle size compared to eating at maintenance.
The physiological rationale for this is intuitive. Providing the body with an excess of energy can facilitate recovery between grueling training sessions, speed up the replenishment of muscle glycogen stores, and allow athletes to train harder or maintain a higher overall training volume. All of these factors theoretically support the process of muscle hypertrophy.
Yet, when researchers parse the data closely, the actual performance gap between a mild caloric surplus and strict maintenance is considerably smaller than many fitness enthusiasts assume. Much of the scientific literature relies on indirect measurements of hypertrophy, such as changes in fat-free or lean body mass. These metrics can easily be influenced by factors other than pure muscle growth, such as increased water retention or glycogen storage brought on simply by consuming more food.
Furthermore, clinical trials demonstrate that significant muscle gain can still occur even when energy intake is tightly controlled at maintenance levels. In a comprehensive meta-regression analyzing 52 separate training studies, researcher Murphy and his colleagues observed that while a caloric deficit clearly impairs the body’s ability to build new muscle tissue, the vast majority of participants who trained while eating at maintenance successfully increased their lean body mass.
This trend becomes even more apparent when looking at the broader landscape of exercise science. Across hundreds of resistance-training studies conducted over the decades, participants are rarely placed on meticulously calculated diets. Instead, they are simply instructed to maintain their usual dietary habits while following a progressive lifting program. In these studies, bodyweight typically remains remarkably stable from baseline to post-testing. Yet, those exact same trials almost universally report that participants simultaneously increase their muscle size and reduce their total fat mass.
While a well-managed caloric surplus might optimize outcomes in specific scenarios, the empirical evidence demonstrates that body recomposition is a regular, repeatable biological phenomenon that frequently occurs under maintenance conditions.
A major driver behind the insistence on bulking is the widespread misconception regarding the energetic cost of building skeletal muscle. Many athletes assume that the biological process of synthesizing new muscle tissue consumes a massive amount of energy, and that a substantial caloric surplus is therefore an absolute prerequisite to fuel growth.
However, bioenergetic research tells a very different story. A comprehensive review by Slater and colleagues calculated the metabolic cost of building human skeletal muscle mass to be approximately 12.7 to 19.5 kilojoules per gram of muscle tissue. Translated into more familiar nutritional terms, that equates to roughly 3 to 4.6 kilocalories per gram of actual muscle mass synthesized.
To paint a realistic picture, one must also account for the energy density of skeletal muscle tissue itself. Most scientific estimates place this energy density at around 16.7 kilojoules per gram of protein. When these figures are applied to a realistic scenario—such as an average intermediate lifter who manages to gain two to four pounds of pure muscle tissue over the course an entire year—the true energetic cost of depositing that tissue becomes strikingly modest.
Calculations indicate that building that amount of muscle requires a total energy investment of roughly 3,450 to 9,800 kilocalories spread out across an entire year. When broken down to a daily scale, the muscle-building process demands an extra 9 to 27 kilocalories per day.
This revelation is significant for three distinct reasons. First, 27 kilocalories is an extraordinarily small number—roughly equivalent to a single bite of food. Second, attempting to intentionally consume a daily caloric surplus of that precise magnitude is practically impossible in the real world. Commercial food labels naturally vary by several percent even under strictly controlled manufacturing conditions, and human error in estimating energy intake from mixed meals introduces far larger margins of error. Third, that tiny energetic requirement can almost certainly be met endogenously by the human body simply mobilizing a minuscule amount of stored energy from existing glycogen reserves or adipose tissue.
In short, the fundamental act of synthesizing new muscle tissue does not require a measurable, conscious caloric surplus on a day-to-day basis.
Rather than viewing cutting, recomping, and bulking as rigid, mutually exclusive modes of training and dieting, sports scientists suggest it is far more accurate to view them as points along a continuous spectrum of energy balance.
Where an individual falls on that spectrum dictates their physiological adaptations. Being in a caloric deficit maximizes fat loss, but it tends to limit or occasionally reverse the body’s capacity for hypertrophy. Eating at maintenance allows for moderate fat loss and moderate muscle gain to occur simultaneously. Meanwhile, shooting for a deliberate caloric surplus maximizes the rate of hypertrophy, but always comes at the unavoidable cost of some accompanying fat gain.
Where an individual should position themselves on this continuum depends heavily on their current training quality, recovery capacity, and baseline body composition. A person carrying higher levels of body fat naturally possesses a larger reservoir of stored energy to draw from, making body recomposition a smooth and straightforward process. Conversely, someone who is already exceptionally lean may struggle to signal significant muscle growth without introducing a true caloric surplus.
Despite the encouraging data, sports scientists emphasize that certain caveats and limitations must be considered. Training status remains a variable of interest, though its exact role in recomposition is still debated. Most studies investigating energy balance and hypertrophy involve relatively untrained or intermediate lifters. As an athlete advances deeper into their training career, the total rate of natural muscle gain slows down dramatically. This deceleration makes body recomposition a slower process for advanced lifters, but it does not render it impossible. In practical terms, both traditional bulking and body recomping yield diminishing returns over time; the primary difference lies in the pacing of the results rather than their fundamental feasibility.
There are also natural biological boundaries governing when recomposition works best. At extremely low body fat levels, maintaining a flat energy balance can signal to the body that growth should be suppressed in favor of survival mechanisms. On the other hand, an individual carrying slightly more body fat has plenty of internal energy reserves to subsidize the protein synthesis process. If an athlete is well below their natural physiological settling point, achieving a recomp will prove considerably more difficult. If they are hovering near or slightly above that settling point, however, recomposition is surprisingly achievable.
Ultimately, the research indicates that body recomposition is far from a myth. It is a documented, predictable outcome observed consistently both in controlled laboratory settings and real-world gym environments. While the magnitude of these physical changes may be modest, particularly for seasoned athletes, the process happens regardless.
For lifters charting their next phase of training, a dedicated bulking phase still holds practical value for those who are relatively lean and comfortable accepting some fat gain in exchange for the fastest possible muscle acquisition. However, for individuals who are already close to their long-term target weight or who simply prefer a steadier, leaner approach to fitness, remaining close to energy maintenance while prioritizing progressive overload in the gym may offer the ideal balance between strength, muscle development, and overall aesthetics.
