Disrupted Sleep Can Stop Fat Burning31 August, 2011 at 10:16 | Posted in Body & Mind, Science | Leave a comment
Tags: Body & Mind, health, Science
I’m a huge advocate of sleep. There is much evidence that demonstrates the importance of sleep’s role in physical and psychological well-being.
In recent years, there has been growing interest in the scientific community regarding sleep and risk of obesity. The data here has shown a U-shaped association, with enhanced risk of obesity seen in individuals who either sleep for very short or very long periods.
Lengthy sleep might be a marker for ill health and enhanced risk of excess weight from conditions such as Type 2 diabetes and low thyroid function. Also, there’s a possibility that long sleepers have relatively sluggish metabolisms and are generally tired and inactive. They risk gaining weight as a result.
What about those short sleepers? These individuals may be tired and sluggish during the day because they’re not getting enough sleep. They may be less active over time as a result.
However, there is also evidence that hormonal changes may play a role. For example, curtailed sleep has been found to raise levels of the appetite stimulating hormone ghrelin and lower levels of the appetite suppressing hormone leptin.
Curtailing sleep has been found to make some people hungrier, prompting them to eat more. It’s also been found to cause insulin resistance, which predisposes to weight gain.
A study published online in the American Journal of Clinical Nutrition on July 27 examined the effects of “sleep fragmentation” on a variety of metabolic processes. A group of young, healthy men were tested in a respiration chamber for two days while they got about eight hours of sleep each night.
On another occasion, the men were awakened by an audible alarm every hour and required to get up to turn the alarm off. This not only interrupted their sleep, but also meant they got less sleep—about 6.5 hours a night compared to about 8.0 hours a night when there was no alarm.
The results of this study showed that the amount of energy these men metabolized when sleep was disturbed was actually a little higher than before. This seemed to be due to increased activity, which the authors attributed to getting up repeatedly during the night.
Scores of exhaustion roughly doubled under the disturbed sleep conditions, and symptoms of sleepiness increased considerably.
Perhaps the most interesting findings from this experiment related to the men’s metabolism, specifically the rate at which the men metabolized carbohydrate and fat.
In moving from uninterrupted to interrupted sleep, carbohydrate metabolism went up from an average 324 to 346 grams per day (statistically significant).
At the same time, fat metabolism dropped from 61 to 29 grams per day. In other words, the rate at which these men burned fat dropped by half over just two nights of interrupted sleep.