Can you build muscle while cutting calories?

Short answer

Yes, if you cut only a little. In a 30-person study, the group that ate 250 kcal less a day while training for 10 weeks lost fat and gained 1 kg of lean mass. But at a cut of about 500 kcal a day, muscle gain stopped.

Can you build muscle while cutting calories?
'Eat less → not enough building material → no muscle gain' — does this formula hold?
A common belief says you must eat a lot to build muscle, and while losing weight the best you can do is keep what you have. We checked whether muscle can grow while eating less, and how big a cut stops it.
On average, gains were smaller
The eat-less side gained less muscle
An analysis that pooled randomized trials of strength training while eating less for more than 3 weeks found that the eat-less groups gained less lean mass (muscle and everything except fat) than groups eating enough. Strength gains, though, were similar on both sides.
The tipping point was about 500 kcal a day
At that cut, lean mass gain stopped
In the same analysis, linking the size of the cut to lean mass change showed that eating about 500 kcal less a day stopped lean mass from growing. For someone eating 2,000 kcal a day, that means dropping to 1,500 kcal.
But a small cut still allowed gains
250 kcal less a day for 10 weeks: up 1 kg
30 people trained 4 times a week for 10 weeks. The group eating 250 kcal less a day lost 2.94 kg of fat while gaining 1.04 kg of lean mass. The group eating at maintenance gained 0.97 kg, and both groups ate a lot of protein.
Speed of weight loss mattered too
Only those who lost slowly gained 2.1% lean mass
24 people who lifted 4 times a week lost the same amount of body weight (about 5.6%). The group losing 0.7% a week slowly gained 2.1% lean mass, while the group aiming for a fast 1.4% a week did not gain any.
Gains happened even with a big cut
40% less for 4 weeks, but only with high protein
40 people ate about 40% less than they needed for 4 weeks while doing strength training and high-intensity intervals 6 days a week. The high-protein group gained 1.2 kg of lean mass, while the lower-protein group barely changed at 0.1 kg.
Adding exercise alone cut losses in half
34 trials, 1,455 people: 45.7% of muscle loss prevented
A 2026 analysis that pooled 34 trials (1,455 people) who added exercise while eating less found that the exercise groups kept 0.87 kg more lean mass. That prevented 45.7% of what they would have lost by dieting alone.
Bottom line: cut a little, lose slowly, and muscle still grew
The formula breaks at 'eat less → no muscle gain'
Cutting about 250 kcal a day and losing 0.7% of body weight a week (about 0.5 kg for a 70 kg (154 lb) person) let strength training add lean mass. Cutting more than 500 kcal a day or losing fast stopped gains on average; the big-cut gain came in a 4-week study with high protein and training 6 days a week.