According to Dr Matthew Walker when your sleep becomes short, you will gain weight.
The first concerns are 2 hormones that control appetite: Leptin and Ghrelin.
Leptin signals sense of feeling full, when leptin levels are high, appetite will be be blunted and we don't feel like eating.
Ghrelin in contrast, triggers a strong sensation of hunger. When Ghrelin levels increase so does hunger.
An imbalance of either one of these hormones can trigger increased eating and thus body weight.
Perturb both in the wrong direction, and weight gain is more than probable.
Over the past 30 years Dr. Eve Van Cauter at the university of Chicago has been conducting research that link sleep and appetite.
Participants that took part in the studies got given a room with a bed, clean sheets, TV and internet access but not tea or coffee as caffeine was not allowed.
In one arm of the experiment, subjects were given an 8 and half hour sleep opportunity each night for 5 nights. recorded with electrodes placed on their head.
In the other arm of the study, the subjects were only allowed 4 to 5 hours sleep for 5 nights, measured the same way.
In both studies they received the same amount and type of food, and their physical activity was kept constant.
Each day the sense of hunger and food intake were monitored, as were circulating levels of leptin and ghrelin.
Van Cauter discovered that individuals were far more ravenous when only sleep 4 to 5 hours per night. This despite being given the same amount of food and being similarly active.
Individuals sleeping 8 or more hours were in control of their hunger.
The strong rise of hunger pangs and increased reported appetite occurred rapidly, by just the second day of short sleeping.
Inadequate sleep decreased leptin and increased ghrelin.
By muting the chemical message that says "STOP EATING" (leptin) yet increasing the hormonal voice that shouts "PLEASE KEEP EATING" (ghrelin), appetite remains unsatisfied when sleep is anything less that plentiful, ever after a good meal.
Another study was conducted on the back of the above but this time participants were given FREE access to food.
The researchers found that the sleep deprived participants ate 300 calories more each day, or well over the 1000 calories before the end of the experiment, compared to those who had a full 8 hours sleep.
Similar changes occur if you give people 5 to 6 hours of sleep per night over a 10 day period. Scale that up to a working year, and assuming one month of holidays in which sleep becomes abundant, and you will still have consumed more than 70,000 extra calories.
That could easily equate to 10 to 15 pounds of weight gain per year, each and every year.
Some argue that we eat more when we are sleep deprived because we burn more calories when we stay awake. Sadly this is not true. In the studies there was no difference in caloric expenditure between the 2 groups.
Inadequate sleep is the perfect recipe for weight gain, greater calorie intake and lower calorie expenditure.
Epidemiological studies have established that people who sleep less are more likely to be overweight or obese.
I know what you are going to ask: Helder what if someone is in a calorie deficit, what happens then?
I will answer this question on the next blog :-)