Back at the beginning of the year, a great many of us resolved that we would lose some weight in 2010. Some of us vowed we would get up early, sacrificing an hour or two of sleep to squeeze in an hour or so of exercise before the rest of our busy schedule hijacked our day. What we didn’t realize was that we may have sabotaged our efforts to lose what we wanted to get rid of –fat– by giving up something our body wanted –sleep.
The results of a new study, published in the Annals of Internal Medicine last week, suggest that getting enough sleep helps us lose fat (1). The study followed 10 overweight individuals over two two-week periods. They were placed on a controlled diet and then spent two weeks with 8.5 hours per night in bed and two weeks with 5.5 hours per night in bed.
The subjects lost an average 6.6 pounds during each two week period. But here is the interesting part; when they got enough sleep, 3.1 pounds of that weight loss was fat, and when they didn’t get enough sleep, they lost only 1.3 pounds of fat. The only difference between the two study periods was a bit more than two hours of sleep, and when they slept more they lost more fat!
What is the explanation for these perhaps unintuitive results? Well it seems that when we don’t get enough sleep, the levels of a hormone called ghrelin increase. And at higher levels, ghrelin reduces energy output and triggers hunger, stimulating food intake. It also promotes fat retention and increases hepatic glucose production. And sure enough, the authors found that when the participants sleep was restricted, they experienced an increase in hunger and their oxidation of fat was reduced.
So what is the message to those of us still hanging tight to that beginning-of-the-year resolution to lose weight? Eat right, exercise and get some sleep.
- Nedeltcheva, A.D. et al. (2010) Insufficient sleep undermines dietary efforts to reduce adiposity. Ann. Intern. Med. 153, 435–441.