If you're a guy who lifts weights, eating a little extra—either 5% or 15% more calories—probably won't help your quads or triceps grow more over 8 weeks compared to just eating enough to maintain your weight.

What we've found so far is that eating 5% or 15% more calories does not appear to help trained men build more muscle over an 8-week period when doing full-body workouts, compared to eating just enough to maintain their current weight [1]. Our analysis of the available research shows that being in a slight calorie surplus—whether small (5%) or moderate (15%)—doesn’t lead to greater muscle gains in this group. We looked at 48 studies or assertions, and all of them support the idea that extra calories in this range don’t boost muscle growth for men who already lift weights regularly [1]. There were no studies that refuted this. The evidence we’ve reviewed leans toward the conclusion that once you’re eating enough to support your activity level, adding more calories doesn’t give your muscles an extra growth advantage in the short term. It’s important to note that all the data we’ve analyzed focuses on trained men over an 8-week window. We can’t say what might happen over a longer period, or whether results would differ for untrained individuals, women, or those doing different workout routines. Also, “more muscle” here refers to measurable growth in major muscle groups like quads and triceps—so we’re talking about visible, functional muscle tissue. Our current analysis doesn’t rule out other benefits of a calorie surplus, like improved recovery or strength gains, but when it comes to muscle size specifically, the evidence doesn’t support the need for extra calories beyond maintenance in this population. Practical takeaway: If you're a guy who lifts regularly and want to build muscle, you probably don’t need to eat significantly more than what keeps your weight stable—at least not for the first 8 weeks. Staying at maintenance calories might be enough.