Besides food intake, exercise and genetic background, it seems that sleep is involved in weight control. While other drivers are taken seriously, lack of sleep is often overlooked. There are two main hormones involved in regulating the appetite and food intake, whose levels vary dramatically during sleep – leptin and ghrelin.
What Do These Hormones Do?
Leptin is a hormone with protein structure, involved in both regulating the metabolism and appetite, as well as burning calories. The hormone is produced by the fat tissue and interacts with a number of receptors, especially in the ventromedial hypothalamic nucleus, known as “the appetite center.” Here it signals the sufficient food intake, and satiety. During sleep, hormone levels rise, sending signals that there is enough energy and there is no need to produce more. When you don’t sleep enough, the leptin may decrease its amount so much that it signals the brain to interpret this as an inadequate dietary intake. The signals sent are those of hunger, though there isn’t actually the need of an increased calorie intake. Thus, the calories are stored in the fat tissue, so they can subsequently be used as an energy source.
Ghrelin is a hormone produced by the stomach cells and the pancreatic cells, which stimulates appetite. This hormone is produced by the hypothalamic arcuate nucleus as well, where it also stimulates the growth of hormone secretion. At this level, the cholinergic-dopamine reward system activates, a circuitry that reinforces the need for rewards such as food, but also substances that can lead to addiction. A study showed that short periods of sleep are associated with high levels of this hormone and obesity. The researchers found an inversely proportional relationship between hours of sleep and the serum hormone concentrations.
These two hormones secretion occurs in two different times of day, especially during the night, and the relationship between sleep deprivation and obesity can be explained by a change in the level of these hormones, induced by insufficient sleep.
Jacques Montplaisir, professor in the department of psychiatry and director of the Center for Sleep Problems at Hospital Sacre-Coeur, said that 26% of children who sleep less than 10 hours per night between the ages of 2 years and half and 6 years are overweight. A team of researchers studied 1138 children and found that: 26% are overweighted, 18.5% had a body mass index between 25 and 30 and 7.4% were obese with a BMI over 30.
Another study analyzed the data of 17,000 participants in 1982, and the results were:
- Those who slept about 5 hours a night were 73% more likely to become obese than those who slept 7-9 hours per night,
- Those who slept 6 hours per night were 27% more likely to become obese than those who slept 7-9 hours per night,
- Those who slept only 2-4 hours per night were 67% more likely to become obese.
In reality, scientists say that further research in this area is needed, but for now the prospect of new therapies in case of obesity is taking shape; there therapies are based mainly on diet changes and sleep adjustments. For now, besides diets, surgical interventions also have a large success among the people who are obese.
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