Does extra protein help with losing weight without losing muscle?

Eating extra protein while losing weight helps preserve muscle mass, but the effect depends strongly on whether you also exercise alongside it. The combination of adequate protein and resistance training has been shown to be most effective: together they lead to preservation or even a slight increase in muscle mass, whereas protein or training alone has a clearly more limited effect.

For most healthy adults and athletes who want to lose weight without losing muscle, multiple studies point to an intake of 1.6 to 2.4 grams of protein per kilogram of body weight per day. Highly muscular, lean athletes who train intensively with weights may need to go even higher. The larger the calorie deficit and the more demanding the training, the more protein you need to protect your muscles.

In older adults (55-80 years), the picture is less encouraging: a higher protein intake without resistance training did not lead to significantly less muscle loss in an RCT of one hundred participants. Only the combination of higher protein plus resistance training produced a measurable difference (+0.6 kg of fat-free mass). For older people, exercise is therefore not an optional extra but a requirement in order to see the effect of additional protein.

Protein alone does not improve muscle strength, only muscle mass. Excessively high intakes can also have adverse metabolic effects, although the threshold for this was not precisely established in these studies. The protein source may also play a role: whey protein and plant-based proteins have been studied in people with obesity, but there are still very few long-term human studies available to make firm statements about which source works best.