Could insufficient sleep be causing weight gain?

As more studies reveal a clear link between sleep deprivation and weight gain, it becomes increasingly hard to ignore the cause-and-effect connection. Those who sleep at least seven hours per night generally have less body fat compared to those who don't. While other factors like food consumption, exercise, and genetics also play a role in weight gain, sleep proves to be more crucial than many realize. For example, in the NHANES I study involving 9,000 participants between 1982 and 1984, it was found that individuals averaging six hours of sleep nightly were 27% more likely to be overweight, and those who averaged five hours were 73% more likely to carry excess weight.

A lot of people who are sleep deprived don't even realize it. Many believe there's flexibility in how much sleep one needs to remain healthy and functional, but most experts agree that seven hours is the minimum requirement for everyone except the very young and elderly. Besides the number of hours, here are some signs to determine if you're sleep-deprived:

Normally, individuals who aren't sleep-deprived take about 15 minutes to fall asleep. Chronic sleepiness and falling asleep almost instantly when you get into bed are strong signs that you're not getting enough rest.

If you're sleep deprived, the connection to obesity becomes apparent, such as constant tiredness making it hard to engage in physical activities. But there are also several internal processes happening in your body that could lead to weight gain. Scientific research frequently points to hormonal imbalances, especially with the hormones leptin and ghrelin, as the most significant effects of sleep deprivation.

When you don't sleep enough, your body experiences a shortage of leptin and an overproduction of ghrelin.

Leptin and Ghrelin

The hormone leptin plays a crucial role in controlling appetite, metabolism, and calorie burning. It signals your brain when you're full, when it's time to burn calories, and when to produce energy for your body. This process triggers a chain reaction that begins in the hypothalamus and ends in the thyroid gland, which manages how your body stores and uses energy.

When you sleep, leptin levels rise, signaling to your brain that you have enough energy, meaning there’s no need to feel hungry or burn calories. However, when you don’t get enough sleep, leptin levels drop, causing your brain to think you're low on energy. Consequently, your brain tells you you're hungry, even if you don't actually need food, and it starts storing the calories you eat as fat to ensure you have energy for later. The reduction of leptin caused by sleep deprivation can lead to constant hunger and a slowing metabolism.

The other hormone tied to sleep and weight is ghrelin, which has an effect opposite to leptin. It signals your brain when to eat, when to stop burning calories, and when to store energy as fat. Ghrelin levels drop during sleep since sleep requires less energy than being awake. However, individuals who don’t sleep enough tend to have excessive ghrelin, making the body think it's hungry and in need of more calories, halting calorie burning because the body assumes there’s an energy shortage.

Some researchers suggest that these hormonal fluctuations during sleep are part of an evolutionary adaptation that helped humans survive food shortages during winter. Traditionally, winters are marked by long nights and scarce food, while summers offer short nights and plenty of food. Shorter nights lead to less sleep, lower leptin, and higher ghrelin, prompting the body to eat as much as possible and store calories for winter. Conversely, winter brings more sleep, increasing leptin and decreasing ghrelin, signaling the body to burn the calories it stored during the summer.

Sleep deprivation has been shown to raise levels of stress hormones and insulin resistance, both of which contribute to weight gain. Insulin resistance can also increase the risk of type 2 diabetes.

The National Sleep Foundation provides these helpful suggestions to ensure you get enough rest for your body to function at its best: