Even when cutting calories helps people lose weight, they may have a harder time getting rid of excess body fat if they don’t get enough sleep, a small experiment suggests, according to Deccan Chronicle.

Over eight weeks, researchers asked 15 overweight and obese adults to focus only on cutting calories and another 21 participants to both cut calories and get less sleep. Dieters in the sleep-restriction group lost about an hour of rest on each weeknight and then got an extra hour of shuteye on Saturdays and Sundays.

By the end of the experiment, people in both groups had lost about 7 pounds (3.2 kilograms). But in the sleep-restriction group, people lost less fat tissue and more lean muscle.