Whey Protein in a Calorie Deficit: Keep Your Muscle While You Lose Fat

If you want to lose weight, you eat fewer calories than you burn. The catch is that in a calorie deficit your body loses more than fat, it also risks breaking down muscle. This is exactly where protein matters. In this article we look at what a deficit does to your muscle, why a higher protein intake protects it, whether you can even build muscle while losing fat and where a whey shake is useful.

What a calorie deficit does to your muscle

When you take in less energy than you need, your body looks for the missing energy elsewhere. Ideally it pulls it from your fat reserves. But without the right signals it also breaks down muscle mass, because muscle costs energy and a body in shortage wants to save. The result is less weight on the scale, but part of that weight is lost muscle rather than fat.

Two things decide whether your body keeps or loses muscle: a training signal and enough protein. Resistance training tells your body it needs the muscle. Protein supplies the building blocks to keep it. Miss either one and you lose more muscle in a deficit than you need to.

Why more protein in a deficit protects your muscle

In a deficit your protein need rises rather than falls. The reason is that protein is not only used for building, it is also drawn on more heavily as an energy source when food is short. To still have enough left over for keeping muscle, you need more of it. Mettler and colleagues showed in trained athletes that a higher protein intake during a diet clearly reduced the loss of fat free mass.

A systematic review by Helms and colleagues reached a similar conclusion: lean, trained people in a deficit benefit from a protein intake at the upper end of the usual recommendations in order to keep muscle. More protein also has the side benefit of keeping you full, which makes a diet easier to stick to.

Can you even build muscle in a deficit

For a long time the rule was that you either lose weight or build muscle, but not both at once. More recent research shows a more nuanced picture. Longland and colleagues had young men train for four weeks in a clear deficit, one group on a lot of protein, one on little. Both lost fat, but only the high protein group also gained fat free mass. Importantly, the training was hard and combined strength and intervals.

Pasiakos and colleagues likewise found that a higher protein intake after weight loss better maintained muscle protein synthesis. This simultaneous gain works best in beginners, returning trainees or people with more fat to lose. Someone who is already very lean and trained will tend to keep muscle in a deficit rather than clearly build it. But keeping muscle while the fat comes off is exactly the goal.

How much protein in a deficit

For keeping muscle during a diet a range of roughly 1.6 to 2.2 grams of protein per kilo of body weight per day is often mentioned, and the leaner and more trained you are, the closer to the top end. Just as important is the spread: give every meal a decent portion of protein instead of eating it all at dinner, so you switch on muscle maintenance several times a day.

If you want to know how much protein suits your weight and goal, our protein calculator gives you a concrete target to build your day around.

Where whey is useful in a deficit

On a diet you have fewer calories to spend, so every one counts. Whey delivers a lot of protein for few calories and barely any fat or sugar, which makes it especially practical in a deficit. It helps you reach your protein target without blowing your calorie budget.

A whey shake is mainly useful on days when you would otherwise fall short on protein, or around your training. It stays an addition to real meals built on meat, fish, eggs, dairy or legumes. Combine enough protein with resistance training, and you spend your tight calorie budget on keeping your muscle.

Conclusion

A calorie deficit makes you lose weight, but without countermeasures it also costs muscle. With enough protein and resistance training you keep your muscle, and under favourable conditions you even gain a little while the fat comes off. Aim for a higher protein intake, spread it across the day and use whey as a low calorie way to reach your goal. That way you lose fat instead of muscle.

Sources

• Longland TM, et al. Higher compared with lower dietary protein during an energy deficit combined with intense exercise promotes greater lean mass gain and fat mass loss: a randomized trial. Am J Clin Nutr. 2016. PubMed 26817506
• Helms ER, et al. A systematic review of dietary protein during caloric restriction in resistance trained lean athletes: a case for higher intakes. Int J Sport Nutr Exerc Metab. 2014. PubMed 24092765
• Pasiakos SM, et al. Effects of high-protein diets on fat-free mass and muscle protein synthesis following weight loss: a randomized controlled trial. FASEB J. 2013. PubMed 23739654
• Mettler S, et al. Increased protein intake reduces lean body mass loss during weight loss in athletes. Med Sci Sports Exerc. 2010. PubMed 19927027