On October 24, 2022, Nature Reviews Endocrinology (IF=47.564), a sub-journal of Nature, published a review that explored the interaction of sleep deprivation and circadian rhythm disorders with obesity, and summarized some strategies that can improve sleep.
Obesity Risk Linked to Lack of Sleep
Insufficient sleep at night will increase 24-hour energy consumption, and for healthy young people, it may lead to a 4% to 5% increase in total daily energy consumption (about 100kal/day). The increased energy expenditure from sleep deprivation can happen quickly and last for many days.
During periods of sleep deprivation, a negative energy balance occurs when energy intake is controlled compared to an increase in energy expenditure. This negative balance, along with changes in levels of orexin hormones (increased gastrin and decreased leptin), increases hunger.
When energy intake is uncontrolled during periods of sleep deprivation, increases in energy intake can outweigh increases in energy expenditure, leading to positive energy balance and weight gain. Meta-analysis showed that compared with the recommended sleep duration, energy intake increased by an average of 253kal/day to 385kal/day when sleep duration was insufficient.
The effect of obesity on sleep
Studies have shown that obese adults are more likely to report sleeping too short or too long compared to non-obese people (7-8 hours/day). Obese adults are more likely to experience sleep problems than those without any comorbidities. Excessive daytime sleepiness has also been reported in severely obese adults without obstructive sleep apnea.
Many physiological factors may affect sleep in obese people. The location of fat tissue may affect the risk of certain sleep disorders. For example, abdominal obesity and a large neck circumference are risk factors for obstructive sleep apnea.
Visceral adipose tissue has also been shown to be associated with cardiovascular disease and type 2 diabetes risk. Behavioral factors such as poor diet and lack of exercise may also have an impact on sleep.
Strategies to Improve Sleep
1. Get some exercise
It is well known that increased levels of exercise are associated with a lower risk of metabolic syndrome. Studies have shown that lack of exercise and lack of sleep have a synergistic effect on the occurrence of metabolic syndrome and increased mortality. Research discourages exercising at night because it can interfere with nighttime sleep. Notably, whether exercise helps prevent or reduce sleep deprivation-related health outcomes is unknown.
2. Eat healthy and avoid eating at night
Healthy dietary patterns are associated with a reduced risk of metabolic syndrome. Healthy eating patterns, especially those similar to the Mediterranean diet, can improve sleep quality. Eating more in the evening can lead to weight gain and obesity and reduce the effectiveness of weight loss programs. A 2022 study showed that a restricted diet implemented by healthy adults had greater benefits on insulin resistance and related metabolic indicators than eating at noon and earlier in the day.
Obese adults were more likely to report sleeping too short or too long compared with non-obese individuals (7-8 hours/day). Obese adults are more likely to experience sleep problems than those without any comorbidities. Excessive daytime sleepiness has also been reported in severely obese adults without obstructive sleep apnea.
3. Light management
Bright light during the day and dim light at night are important for the regulation of circadian rhythms and may benefit metabolism. More research is needed to explore whether increased exposure to bright light during the day (by going outside more often) improves sleep and circadian rhythms, thereby improving metabolic health. Also, studies are needed to determine whether exposure to bright light during nighttime exercise affects sleep. Previous studies have shown that reducing nighttime blue light exposure improves sleep quality, and this strategy may also improve fasting blood sugar levels and insulin resistance, which in turn reduces the risk of metabolic syndrome, but more research is needed to confirm.
4. Avoid coffee at night
Observational studies have shown that coffee drinkers appear to have a lower risk of obesity, metabolic syndrome, and type 2 diabetes compared with non-coffee drinkers. However, drinking coffee at night can disrupt sleep. The study found that in healthy adults, consuming 400 mg of caffeine 6 hours before bedtime reduced sleep by more than 1 hour. Caffeine may also lead to later bedtime and changes in circadian rhythms. More research is needed to determine the benefits of drinking coffee earlier in the day versus later in the day on sleep, circadian rhythm, and metabolism.
5. Take naps during the day
A meta-analysis of daytime naps found a J-shaped association between nap duration and the risk of type 2 diabetes and metabolic syndrome, with daytime naps of up to 40 minutes having no effect, and increased nap duration significantly increasing the risk of these diseases. Short naps (10-20 minutes) have wide-ranging health benefits, including improved cognitive function and reduced sleepiness and fatigue. Daytime naps may help reduce the adverse effects of nighttime sleep deprivation on metabolic health when nighttime sleep deprivation occurs, but more research is needed to confirm these findings.
6. Limit alcohol consumption and no smoking
Alcohol consumption in adults interacts with reduced sleep duration and increases risk of abnormal blood sugar, study finds. Smoking is associated with a risk of developing metabolic syndrome, and smoking cessation appears to reduce this risk. Compared with non-smokers, smokers, especially those who smoke at night, have longer sleep latency, more awakenings, poorer sleep quality, and shorter sleep duration. It is recommended not to smoke and to limit alcohol consumption, especially when going to bed, for healthy sleep and optimal metabolic regulation.
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