When your goal is to lose body fat, you’d expect to make changes to diet and exercise. But you might not think of factoring in sleep.

It’s time to wake up – or rather, go to sleep – because a lack of sleep might be the reason you’re not losing weight or ridding body fat as easily.

Even a moderate amount of sleep loss during the week is enough to prevent body fat loss. Worse yet, “catch-up” sleep on the weekend isn’t likely to completely reverse the havoc that moderate sleep loss during the week can cause your body.

In a study from Arizona State University, scientists found that when overweight individuals skimped out on sleep for just one hour for up to five nights per week, they lost less body fat during a structured weight loss program lasting eight weeks (1).

Moreover, no amount of “catch-up” sleep on their other two days was enough to reverse the effects of sleep loss throughout the week (1).

Sleep Loss Can Drastically Affect Your Physiology

In the study, the subjects who were sleep deprived lost about the same amount of total weight as compared to the control group following the same weight loss regimen. But their loss of less body fat was combined with more loss of lean body mass.

The findings suggest that sleep loss of just 60 minutes five days a week caused a shift in how the body responds to calorie restriction, including changing the balance of appetite hormones (leptin and ghrelin) as well as insulin sensitivity. The extra sleep the subjects received over the weekend didn’t have any overall effect on these differences.

Scientists have long known sleep loss can dramatically affect a person’s physiology. For example, previous studies evaluating sleep restriction found that it can alter the balance of hormones that are involved in controlling appetite, calorie intake, and metabolism (2-4).

These effects of sleep loss might also explain why observational research has shown that there’s a strong link between insufficient sleep and being overweight (1-4). Additionally, short-term studies have demonstrated that getting more sleep was positively associated with achieving success while on a weight loss regimen (1-4).

This new ASU study reported for the first time that moderate sleep restriction was enough to make an impact on body composition. Cutting back on calories is still what matters most for losing weight, but sleep may affect the overall quality of the total weight loss.

Saying Good Night to Hunger

Because hunger itself is a factor in interfering with sleep during a weight loss program, the study raises questions about the need for managing appetite during a weight loss period. Sleep restriction can also exacerbate the relevance of hunger and cravings.

The sleep-deprived subjects might’ve been inclined to eat more food beyond what they received as prepared lunches and dinners. The study also didn’t account for meal timing, which may itself have effects on metabolism.

Among the several strategies for managing hunger during a weight loss program is to adopt meal-timing strategies, such as the pacing of protein intake over the course of the day. Smart snacking and consuming protein at bedtime could also be important for improving the quality of sleep.


  1. Wang X, Sparks JR, Bowyer KP, Youngstedt SD. Influence of sleep restriction on weight loss outcomes associated with caloric restriction. Sleep [Internet]. 2018;1–11. Available from: https://academic.oup.com/sleep/advance-article/doi/10.1093/sleep/zsy027/4846324
  2. St-Onge MP. Sleep-obesity relation: underlying mechanisms and consequences for treatment. Obes Rev. 2017;18 (Suppl 1):34–39.
  3. Hibi M, et al. Effect of shortened sleep on energy expend- iture, core body temperature, and appetite: a human ran- domised crossover trial. Sci Rep. 2017;7:39640.
  4. Wang X, et al. Short-term moderate sleep restriction decreases insulin sensitivity in young healthy adults. Sleep Health.