Evidence is mounting that lack of sleep can lead to metabolic disorders, heart disease, or even cancer. Though the exact underlying mechanism is unclear, there seems to be a connection between sleep, circadian rhythm, and the body's metabolic systems.
Physical, mental and behavioural changes that follow a 24-hour cycle are referred to as circadian rhythms. These rhythms, found in mammals including human beings, are generated in a part of the brain called anterior hypothalamus. They orchestrate sleep and wakefulness, feeding and energy expenditure, and glucose metabolism.
AdvertisementStudies show that changes in our eating and sleeping patterns can shift circadian rhythms. A week of poor sleep can disrupt our body's intricate physiological timings. One analysis showed that insufficient sleep alters the expression of about 711 genes in our body.
Melatonin, a hormone that regulates sleep and wake cycles, is believed to be an important factor that links circadian timing and insulin production, lack of which leads to diabetes. Interestingly, the production of melatonin is suppressed by light; it peaks around 3 to 5 hours after sleep onset. The introduction of artificial light and activity into night-time hours can thus alter melatonin synthesis. A 2013 study within the Nurses' Health Study cohort showed that, women with a low production of melatonin are at high risks of developing type-2 diabetes. Night-shift workers with irregular and extended working hours also face similar risks. Whether melatonin supplementation has a role in treatment of diabetes is still being studied.
Abnormal eating behaviors, particularly night-time eating, have also shown to contribute to sleep loss leading to weight gain and obesity. Insufficient sleep increases energy expenditure and this is compensated by increased food intake. People with sleep-loss often resort to after-dinner snacks that are high in calories (about 42 percent calories more than what they obtain from the smaller breakfasts that they have). Night-time eating may alter our circadian rhythm by delaying the onset of melatonin secretion at night. Insufficient sleep is also known to disrupt the signalling of satiety and hunger hormones leading to overeating.
Obesity, a pandemic, is more rampant in modern times. Life in the modern era of competition lays unfathomable stress on people, the working class to be more specific. 'A disrupted sleep schedule, a physiological drive for more food intake, the availability of high-calorie foods, and exhaustion leading to less physical activity overall' may all contribute to weight gain, suggests a recent article in Lancet, a leading medical journal.
Reference: Interlinks between sleep and metabolism; Jill Jouret April 2013.