The connection between losing weight and sleep
These days, everyone wants to lose a few pounds, and getting a little more shut-eye may help some people. But, the relationship between sleep and weight is a complicated one.
The medical community and researchers know that adequate sleep has many important roles in our daily lives; it is a part of a healthy lifestyle. Perhaps, the most important role sleep plays relate to our cognitive functioning/memory. Without enough sleep, we cannot do well in school or work or social environments. We are also more likely to get into an accident if we cut back on sleep because our reaction time increases. We are also likely to make more errors without sufficient sleep, and sometimes these mistakes can have grim consequences. Accidents and decreased performance are short-term consequences of sleep deprivation, but let’s discuss some longer-term effects of modest sleep deprivation on body weight.
Adequate sleep helps regulate our hunger and satiety hormones, ghrelin and leptin.1 There are other appetites regulating proteins/hormones that are also be affected by sleep, but let’s focus on these two for now. Ghrelin is released from the stomach, and it signals our brain that we are hungry. When we are not sleeping enough or getting poor quality sleep, the level of ghrelin in our body increases subtly. In people living with obesity (a chronic disease of excessive body fat that affects the health of the individual adversely), ghrelin releases may be at a higher than normal—and as a result, there may be more hunger. But, the decreased sleep could cause more weight gain by increasing the hunger hormone as well.2 Leptin is released from our fat issue. Some research suggests more leptin is released in those living with obesity, which results in leptin resistance—the body does not recognize the presence of leptin, and thus, the sensation of satiety is minimized, potentially causing people to overeat because the body cannot understand the hormonal cues.3 The concept of leptin resistance is similar to that of insulin resistance where the decreased insulin sensitively in tissues over time leads to diabetes because it causes higher levels of circulating plasma glucose.
The cyclic relationship between adequate sleep and physical activity is well known. Engaging in physical activity improves sleep, and obtaining adequate sleep improves our capacity to participate in physical activity. In fact, those who sleep 7-8 hours per night are known to have higher physical activity level than those who sleep less than 7 hour or more than 9 hours per night (Figure 1-less people sleeping 7-8 hours per night are physically inactive).4 We do not, however, need to engage in high-intensity physical activity to see beneficial effects; moderate level activities, such as, brisk walking for 30 minutes a day, can result in the positive effects.
What is more interesting for me is the effect sleep has on foods choices. Research suggests that we are more likely to choose healthier foods if we get sufficient sleep.5 Studies in humans also demonstrate that sleep deprived people would consume as much as 600 more calories (mainly from calorie-dense foods) than non-sleep-deprived people. So, if we are sleep deficient, we are more hungry, and we will choose the higher calorie foods that are often rich in simple carbohydrates and fats. But, we only need a small but prolonged increases in calorie consumption to start seeking our body weight go up.
Finally, emerging research is revealing the importance of another key factor that affects both sleep and body weight: our circadian clock, the 24-h internal clock. Research suggests that if our circadian clock is misaligned, regardless of how little we eat or how much more exercise we do, we will gain weight. Our modern society makes it too easy for humans to work against our circadian clock because we have 24-h conveniences that allow us to continue living, working, and eating whenever we want. This is a possible explanation for the higher cardiometabolic disease risks, such as diabetes, hypertension, cholesterol, and heart disease, found in shift workers.6 Additionally, the shortwave blue lights emitted from our Smartphones, laptops, and TV screens, can disrupt our sleep and the circadian clock. Because we have lights 24-h a day in both our indoor and outdoor environments, we can not only have an active social life 24-h a day, we are also regularly exposed to the light pollution that results in circadian rhythm misalignment.
Therefore, to lose weight, it is important to get not only adequate sleep but also to make sure our circadian clock is aligned. This includes making lifestyle changes, such as engaging in the more physical activity, choosing a healthy diet, sleep during night hours, working during daytime hours, curbing our social life during the late evening hours, and thus, minimizing the adverse effects of social jet lag, and eliminating technology uses prior to our bedtime. Even if we make all of these changes, our success is not guaranteed, but we will fare better than the average adult in developed countries.