How does a sedentary lifestyle increase the risk of obesity?

A sedentary lifestyle increases the risk of obesity primarily by creating an energy imbalance, where caloric intake exceeds the body's energy expenditure. According to the law of conservation of energy, when the body consumes more energy than it burns, the excess is stored as fat.1

Physical activity is the most variable component of daily energy expenditure, accounting for 20 to 40 percent of the total energy used by the body. In sedentary individuals, this expenditure is significantly reduced, lowering the total number of calories burned throughout the day. Modern environmental factors, such as increased screen time, digital gaming, and reliance on driving, have reduced the societal necessity for physical movement, further contributing to weight gain.123

Beyond the direct impact on caloric balance, a lack of exercise is associated with the loss of muscle mass, which can further decrease metabolic activity. Addressing obesity requires recognizing the importance of increasing physical activity and monitoring dietary choices to restore a healthy energy balance.432