Sleep restriction hinders weight loss even when calories are reduced.
Sleep deprivation is terrible for your physical and mental health. Poor sleep habits lead to higher stress levels and higher levels of cortisol. Cortisol is a stress hormone that also leads to higher fat stores and hunger. Multiple studies have shown that stress and poor sleep leads to higher body fat and stress, but few have looked at sleep deprivation in the absence of increased caloric intake.
In 2018, researchers looked at this very question. In the study, researchers examined the effects of moderate sleep restriction on body weight, body composition, and metabolism while maintaining caloric restriction. The study enrolled 36 overweight or obese adults who were randomized to an 8-week caloric restriction regimen alone or combined with sleep restriction. All participants were instructed to restrict daily calorie intake to 95 per cent of their measured resting metabolic rate. Participants in the restricted sleep group were also instructed to reduce time in bed on five nights.
The researchers found that the sleep-restricted group tried to increase sleep the other two days fo the week to catch up but still experienced a weekly deficit of sleep. Both groups lost weight, lean mass, and fat mass, however, the proportion of total mass lost as fat was significantly lower in the restricted sleep group.
The bottom line: One hour of sleep restriction for five nights a week led to less proportion of fat mass loss despite undergoing hypocaloric weight loss. Catch up sleep did not appear to affect this metabolic change. A more extensive study is needed, but this study points to a recommendation to get more sleep if you are trying to lose weight.