Experts warn poor sleep cycle linked to metabolic disorders

The term ‘circadian’ means ‘around’ and ‘day’, respectively.
The circadian cycle in humans, also known as the circadian rhythm or internal clock, is a natural process in the body that regulates various physiological functions such as the secretion of hormones (eg, cortisol and growth hormones), body temperature, feeding behaviour, digestion, energy metabolism, change in insulin sensitivity and the sleep-wake cycle.
A part of the brain, known as the hypothalamus, contains a suprachiasmatic nucleus that regulates the body's circadian rhythm over 24 hours.
Many factors influence circadian rhythm. These factors include light-dark cycles, temperature and food intake.
The peripheral clock is located in various organs, including the organs such as pancreas, liver, gastrointestinal tract, muscle and body fat.
Both internal and peripheral clocks regulate metabolic homeostasis. Circadian rhythm plays an important role in various metabolic processes, including the production of glucose, secretion, and sensitivity of insulin.
During sleep, the circadian rhythm may help the liver to break down glycogen in order to produce glucose. In the morning, when we wake up, the internal clock also helps produce cortisol and growth hormones. These hormones help boost the glucose output, which is needed for energy immediately after we wake up.
The sensitivity of insulin is at its peak in the morning and gradually decreases in the evening. The peripheral clock and the glucokinase enzymes are responsible for the fluctuation in the blood sugar levels.
Hence, the meal timings are very important for glucose metabolism. Heavy meals should only be taken during the day when insulin sensitivity is better. Binge eating at night should be avoided. Heavy meals at night alter the glucose metabolism, cause insulin resistance, and may be detrimental to health. Hence, it has been rightly said by many that 'Eat breakfast like a king, lunch like a prince, and dinner like a pauper.'
The suprachiasmatic nucleus is sensitive to light. Light affects the circadian rhythm, sleep regulation and the waking mechanisms. After entering the eye, light sends a signal to the brain to stop the production of melatonin. The melatonin hormone is secreted at night, and exposure to light suppresses its secretion.
Disruption of the circadian rhythm leads to disturbances in the sleep-wake cycle, jet lag and sleep disorders in shift workers, and altered glucose metabolism.
When we consume meals at night, glucose tolerance and insulin sensitivity are reduced, and the level of the circulating hormone melatonin is higher; postprandial glucose and insulin responses can increase.
Disturbed sleep also affects insulin sensitivity. The function of pancreatic beta cells is impaired, resulting in hyperglycemia. A hyperglycemic state is the initial step that leads to type-2 diabetes mellitus.
Hormones such as leptin and ghrelin are related to hunger and satiety. Sleep reduction and circadian rhythm disturbance result in altered levels of leptin and ghrelin. These disturbances give rise to increased appetite and overeating.
A longer circadian rhythm duration leads to obesity and metabolic syndrome. Metabolic syndrome refers to a condition characterised by the triad of obesity, hyperglycemia and hypertension.
Gastric emptying decreases at night. There is also delayed gastric motility, which means the nutrients delivered to the intestine also decrease, and there is a likelihood of metabolic disturbances in the body.
The glycemic response is altered.
In conclusion, it is important for everyone to set a 24-hour schedule that is helpful for the body. We should lead a disciplined life according to a fixed routine.
Adequate physical activity should be performed during the day. Light exposure should be higher during the daytime than at night. We should have good sleep and not stay awake late at night.
Before going to bed, exposure to TV, mobile phones and electronic gadgets, which increase the light screen time, should be avoided. It is always advisable to eat less at night and have adequate sleep, or else there are high chances of developing type-2 diabetes mellitus.