Reducing sleep time by 80 minutes per night has shown the potential to cause changes in both body weight and behavior, according to a study published in July in the journal Annals of Internal Medicine. This finding reinforces the importance of maintaining adequate sleep as part of a healthy lifestyle to aid in reducing weight gain.
The researchers based their analysis on data collected from two randomized clinical trials involving 95 adults who typically slept seven hours or more per night and had a high cardiometabolic risk. The study was conducted in two six-week phases: initially, volunteers maintained their normal sleep habits; subsequently, they reduced their rest time by just over an hour.
As a result of this sleep restriction, an average gain of 450 grams was observed, along with an average increase of 0.5 centimeters in waist circumference. Additionally, participants spent 17 minutes more daily in sedentary activities. Endocrinologist Gustavo Daher, from Einstein Israelite Hospital, emphasizes that because the study was conducted with a small group in a controlled environment, the average gain found should not be excessively generalized.
Sleep plays a crucial role in regulating various bodily processes. During the night, the body operates under a biological clock known as the circadian rhythm, which organizes the secretion of different hormones. Insufficient, irregular, or low-quality sleep can destabilize this function.
Among the regulated hormones are ghrelin, responsible for stimulating hunger, and leptin, linked to the feeling of satiety. Modifications also occur in cortisol, a hormone that generally has lower levels in the early morning hours. According to Daher, the absence of this expected organization of rest and recovery can lead to an imbalance between hormones that induce hunger and those that promote satiety.
The effects of sleep limitation go beyond nutrition. Poor sleep can also result in fatigue and decreased motivation for physical exercise and daily tasks, which helps explain the increase in sedentary behavior observed in the study participants. The endocrinologist assesses that individuals who sleep little or poorly often have less energy and lower functional capacity, and sleep deprivation is correlated with poorer cognitive performance and less healthy food choices, in addition to reducing physical disposition.
The consequences of shorter sleep may extend beyond weight gain, as these alterations in the circadian rhythm can also impact insulin sensitivity and glycemic control. Previous analyses conducted with the same participants in these studies have already indicated a deterioration in insulin sensitivity in women subjected to sleep restriction, particularly after menopause.
Gustavo Daher emphasizes that sleep should have importance comparable to diet and physical exercise in the context of preventing and treating obesity and metabolic diseases, classifying it as one of the pillars of a healthy lifestyle. The medical recommendation is to sleep between seven and eight hours per night, warning that less than six hours can cause metabolic, cognitive, and behavioral harm.
However, regularity, timing, and quality of sleep are as important as quantity. Trying to make up lost hours on weekends does not fully solve the problem, as this pattern, called 'social jet lag,' does not work as a simple addition of hours. The Einstein doctor warns that the circadian rhythm requires continuity, and that sleeping very well for a few days does not compensate for a previous sleep deficit.
Other crucial guidelines include avoiding caffeine and other stimulants close to bedtime and limiting nighttime exposure to electronic devices such as cell phones, computers, and televisions. The light emitted by screens can interfere with the production of melatonin, a hormone essential for preparing the body for sleep. Daher advises maintaining good sleep hygiene, aiming for a minimum of seven hours of rest whenever possible.