Traditional weight loss programs often focus on cutting body fat and hitting lower numbers on the scale but do not focus on gaining muscles. Body recomposition is an approach toward weight loss, where the significance of both losing fat and gaining muscles at the same time is highlighted.¹ Thus, building muscle and losing fat concomitantly has been referred to as body recomposition by practitioners.² 

These positive body composition changes have a multitude of health benefits and have also been shown to improve athletic performance. ² 

High body fat has been linked to several health issues; further high body fat increases the risk of chronic conditions, such as diabetes, cancer and heart disease. On the other hand, having a healthy ratio of muscle mass to body fat can improve health while decreasing the risk of the above diseases. When done correctly, body recomposition changes the makeup of the body so that you have less fat and more muscle. Apart from cutting down body fat, using body recomposition techniques may help one increase strength and boost the number of calories a person burns throughout the day. ¹ 

The ratio of muscle to fat is the best indicator of overall health and fitness. Further, increasing muscle mass boosts the resting metabolic rate (RMR), meaning that one burns more calories while at rest.¹

There are 2 significant factors that influence body recomposition: Progressive resistance training coupled with evidence-based nutritional strategies.²

Adjusting nutritional intake is common in individuals who want to maximize the gains derived from resistance training. Further, research demonstrates that the combination of both resistance training and aerobic exercise can aid in optimum body recomposition. When dietary factors such as energy and macronutrient balance are combined with resistance training, body recomposition is greatly enhanced. Evidence shows that resistance training combined with high dietary protein intake aids in higher body recomposition.²  

A common practice is that caloric deficits are recommended/prescribed for individuals seeking to lose fat mass and caloric surpluses for those aiming to maximize muscle mass accrual. However, evidence challenges this approach and suggests there may be alternative strategies to improve body composition. For example, data demonstrates significant gain of free fat mass and reduction in fat mass when in a state of caloric surplus. Further studies on hypocaloric states have demonstrated significant body recomposition. 

The mechanisms involved in the body recomposition phenomena are not well understood. For example, the precise energy cost of skeletal muscle growth is not fully known. In addition, there is no clear understanding on how the magnitude of energy supply, specifically endogenous sources (i.e., internal fat stores/body fat levels) and exogenous fuel (i.e., diet), pertain to this process.² 

Research shows that different nutritional strategies such as high-protein diets, hypocaloric diets, etc. can elicit body recomposition.² 

Thus, body composition changes is more complex than energy balance alone. While deeper insights are required, additional factors such as sleep (i.e., quality and quantity), stress hormones (e.g., cortisol), androgenic hormones (e.g., testosterone), and metabolic rate can influence changes in body composition.²