Explain why can lack of sleep lead to weight gain?

Disruption of appetite-regulating hormones

When you don't get enough sleep, your body slightly disrupts the hormones responsible for managing hunger. Ghrelin, the one that screams "I'm hungry!", skyrockets and drives you to eat more than necessary. In contrast, leptin, which is supposed to curb your appetite by signaling to your brain that you are full, drops sharply. The result: you eat more without really realizing it, and you are then quite easily at risk of gaining excess weight.

Negative impact on energy metabolism

When you lack sleep, your body tends to slow down the way it burns calories, known as the basal metabolism. This means that even at rest, you burn less energy. Naturally, you store fat more easily instead of using it as fuel. Your body also becomes less efficient at managing blood sugar, thus promoting insulin resistance, which makes fat storage, especially around the belly, more likely. In short, less sleep = less efficient body, calories burned slowly, and easier fat storage.

Modification of dietary choices and sweet cravings

Insufficient sleep directly alters our food preferences. Without proper sleep, the brain craves more fatty, sugary, or salty foods, leading to frequent and hard-to-control cravings. In short, when tired, you’re more likely to give in to snacks, cookies, or sugary drinks. Less sleep also affects the brain areas related to decision-making. As a result, we resist less and give in more quickly to comfort foods at the expense of healthy foods like vegetables or fruits. This is a guaranteed path to an unbalanced and often overly caloric diet.

Decrease in physical activity and available energy

When you lack sleep, your body is exhausted, and you easily lose your motivation to move and exercise. Your energy drops, so it makes sense that you move significantly less. You spend more time sitting or slumped on a couch. As a result, you burn fewer calories daily, which inevitably leads to weight gain. Your usual pace becomes slow, you feel heavy and lazy, and the slightest effort seems enormous. This vicious cycle causes fatigue to settle in for the long term and further exacerbates the lack of physical activity. The less you exert yourself, the more you store your unused energy in the form of fat.

Increased stress and triggering of unhealthy eating habits

Lack of sleep stresses the body and increases the production of cortisol, the stress hormone. When cortisol rises, we often feel an irresistible craving for fatty and sugary foods, typical comfort foods in times of stress. We snack more, choose higher-calorie foods, and these small deviations can quickly become hard-to-control habits. Furthermore, when we are stressed, we tend to eat more impulsively, without really listening to our true hunger, which clearly promotes weight gain in the long term.