The recommended sleep time for people 18-60 years old is about 7-9 hours, an average of 7.5 hours per night. Getting enough sleep helps the body stay physically and mentally healthy.
When staying up late or not getting enough sleep, the two hormones that control hunger and fullness, ghrelin and leptin, are out of balance. The main function of ghrelin is to stimulate appetite, leading to eating and absorbing more calories and storing more fat. Leptin transmits to the brain information that the body has enough fat stores, curbs appetite, signals calorie burning and prevents overeating.
Lack of sleep increases the secretion of the hormone ghrelin, stimulates hunger, and reduces the saturation hormone leptin. At this time, you crave more food, leading to an increase in food intake.
Stanford University research on 1,020 volunteers, published in the American Library of Medicine, showed that people who sleep less are associated with increased BMI (body mass index). People who sleep less than 5 hours per night have 15.5% lower leptin levels and 14.9% higher ghrelin levels than people who sleep 8 hours.
Staying up late and not getting enough sleep also causes abnormal secretion of the hormone cortisol. Cortisol is a hormone secreted by the adrenal glands, playing an important role in stress response, energy management, and regulating many physiological processes of the body. Increased cortisol hormone due to staying up late causes belly fat to accumulate, promoting appetite.
Research in Japan, on 2,000 workers over a period of 7 years, showed that sleep time affects eating habits. Specifically, people who sleep less tend to eat snacks, eat less vegetables, like to eat spicy foods and often eat out. This habit leads to daily calorie intake exceeding necessary calorie needs, causing weight gain.
Staying up late disrupts the circadian rhythm, affecting sleep quality – a factor that prevents the body from being restored and balanced. People who stay up late are often less active during the day because they feel tired, reducing total calorie consumption and increasing the risk of overweight and obesity.
To keep your body healthy and control your weight, you should balance your work, sleep and have a healthy diet. If you often work at night and need to replenish energy, you should prioritize nuts, low-sugar fruits, and filtered water, instead of fast food like chips and soft drinks.