Health Claims

If you're an untrained adult with extra weight, doing strength training for 12 weeks while eating less and getting enough protein (at least 1.4g per kg of body weight) can improve your muscle quality. This improvement shows up as cleaner-looking muscles on an ultrasound, and it doesn’t matter whether you cut calories every day or just on two days a week.

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.

For people with extra weight who are lifting weights and eating less, doing 5:2 intermittent fasting works just as well as cutting calories every day when it comes to getting stronger and building muscle endurance over 3 months.

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.

Even if you exercise, your body won't burn more fat over the day if you eat back the calories you burned — it's more about whether you're in a calorie surplus, deficit, or balance than the workout itself.

Even if you're a fit person who burns fat well, riding a bike for an hour at a moderate pace won't help you burn more fat over the next 24 hours if you're eating just enough to match what you burn.

After eating, when adults go for a moderate workout, their bodies burn more carbs over the next 24 hours but don’t burn any more fat — meaning meals push the body to use carbs for energy instead of fat, even with exercise.

If you exercise for an hour at a moderate pace but eat back all the calories you burned, you might still store more fat over the day — even if you're fit or at a healthy weight.

If you exercise for an hour at a moderate pace but eat back all the calories you burned, you won’t burn more fat over the next 24 hours — whether you're lean, overweight, or a trained athlete.

If you're already lifting weights, gaining more overall body weight might help your biceps grow a little more — especially if you're training hard and eating enough, but the link isn't super strong.

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.

If guys who lift weights eat even a little more than they burn, they might still gain some body fat — and eating a lot more makes that even more likely.

If guys who already lift weights gain weight quickly over 8 weeks, they’re more likely to gain fat than muscle — and this study shows that how much weight they gain is closely tied to how much fat they add.

If you're a guy who lifts weights regularly, eating 15% more calories than you burn might help you get stronger on the bench press compared to eating just a little extra or staying even, but it won’t give you an extra boost on squats or leg muscle growth.

If you're someone who lifts weights and trying to lose fat, eating more protein might help you keep or build muscle better — especially if you already have a leaner body to begin with.

When people who lift weights cut calories, men might keep more muscle than women if they eat more protein.

If you're someone who lifts weights and isn't overweight, eating more protein while cutting calories helps you keep more muscle — especially if you base your protein needs on how much muscle you have, not your total weight.

Having someone guide and check in on your exercise and eating habits helps you stick with it, try harder, and track your food more accurately.

You can't say protein alone changes your body shape if other things like workout coaching and overall diet are different between people in the study.

The more calories you burn compared to what you eat, the more fat you'll lose — it's like a math equation for your body.

Even super-fit athletes can gain muscle and lose fat at the same time—if they do the right things with their diet and training.

If you're someone who lifts weights regularly, whether you're eating more or fewer calories than your body needs is one of the biggest factors in how fast you gain muscle or lose fat.

If you have more body fat, you can safely eat fewer calories to lose fat without losing muscle, but if you're already lean, you need to be more careful with how much you cut your calories.

If you're an experienced lifter, keeping your calories steady won't change your body much. To lose fat or gain muscle, you need to eat less or more than your body needs, on purpose.