For people with extra weight who don't exercise much, eating fewer calories every day — while lifting weights and eating lots of protein — might build more leg muscle than doing the 5:2 diet, even if both help keep the same amount of overall muscle.

What we've found so far is that the evidence leans toward continuous calorie restriction combined with resistance training and high protein intake building more leg muscle than the 5:2 intermittent fasting approach in overweight or obese adults who are not regular exercisers [1]. This is based on the single assertion we’ve reviewed so far, which draws from 52 supporting pieces of evidence and none that refute it [1]. Our analysis of the available research suggests that when people with excess weight follow a plan that includes steady calorie reduction, weight lifting, and high protein intake, they may gain more muscle in their legs compared to those on a 5:2 fasting pattern — even if both groups maintain similar levels of total body muscle [1]. The 5:2 approach involves eating normally for five days and restricting calories significantly for two non-consecutive days, while continuous restriction spreads the calorie reduction evenly across the week. We don’t yet know how much of a difference this is, or how it might change over time. Also, the evidence we’ve reviewed so far focuses only on people who aren’t used to exercising, so we can’t say whether these findings apply to more active individuals. Right now, our current analysis shows a clear lean in one direction, but we’re still building our understanding. More data could change or refine what we see. Practical takeaway: If your goal is to build leg muscle while losing weight, eating fewer calories every day — along with lifting weights and eating plenty of protein — might give you an edge over the 5:2 method, based on what we’ve seen so far.