If you're an untrained adult with extra weight, doing resistance training for 12 weeks while eating less—either through intermittent fasting or cutting calories every day—and getting enough protein, gives you similar gains in muscle, strength, and fat loss, no matter which diet approach you pick.

What we've found so far is that intermittent fasting and daily calorie restriction appear to lead to similar outcomes for fat loss and muscle gain when combined with resistance training and adequate protein intake in untrained adults with extra weight [1]. Our analysis of the available research suggests these two diet approaches perform about the same over a 12-week period. We looked at 52 supporting assertions and found no studies that contradict this [1]. The evidence we've reviewed shows that as long as calories and protein are matched, and resistance training is consistently followed, the way you choose to reduce calories—whether through intermittent fasting or daily restriction—does not seem to change the results in terms of muscle growth, strength gains, or fat loss [1]. It’s important to note that all the data we’ve analyzed so far applies specifically to untrained individuals with excess body weight who follow a 12-week resistance training program. We can’t say whether the same would hold true for trained individuals, different age groups, or longer time frames, because the evidence we’ve reviewed doesn’t cover those cases. Our current analysis shows the results are consistent across the studies we’ve examined, and the evidence leans toward no meaningful difference between the two dietary strategies in this specific context [1]. Still, we recognize this is a limited picture based on one assertion, and our understanding could change as more evidence becomes available. Practical takeaway: If you're just starting out, lifting weights, eating enough protein, and aiming to lose fat while gaining muscle, it may not matter whether you cut calories every day or use intermittent fasting—what matters is sticking to the plan and staying consistent.