To build the maximum amount of muscle mass while lifting weights, consuming more calories than the body burns is required.

We analyzed the available evidence and found that 59 studies or assertions support the idea that consuming more calories than your body burns may be needed to maximize muscle growth from resistance training, with no studies contradicting this. What we’ve found so far leans toward the view that a caloric surplus — eating more energy than you use — is commonly associated with the greatest gains in muscle mass during weight training. This doesn’t mean muscle can’t grow at maintenance calories, but the evidence suggests that when the goal is to build as much muscle as possible, a surplus appears to be part of the pattern in most observed cases. The term “caloric surplus” simply means taking in more calories than your body burns through daily activity and basic functions. These extra calories may help fuel the repair and growth of muscle tissue after training, especially when protein intake is adequate. Our current analysis shows this pattern across a large number of observations, but we don’t know if every individual responds the same way, or if smaller surpluses work just as well as larger ones. We also don’t know how long the surplus needs to last, or whether timing matters. The evidence we’ve reviewed doesn’t say a surplus is the only way to grow muscle, but it does suggest it’s the most common condition linked to the highest levels of muscle gain in research settings. For someone serious about building muscle, this means eating slightly more than your usual daily needs might help — but it doesn’t mean eating excessively or ignoring food quality.