Overweight and obesity are caused primarily by an imbalance between energy intake (calories consumed through diet) and energy expenditure (calories burned through physical activity). When people consume more calories than they burn, the excess energy is stored in the body as fat, leading to weight gain and potentially obesity. Several factors contribute to this imbalance and the development of overweight and obesity:
- Dietary factors: Consuming high-calorie diets, particularly those rich in fat, sugar, processed foods, large portion sizes, sugary beverages, and alcohol can lead to excess calorie intake.
- Physical inactivity: Lack of sufficient physical activity reduces the number of calories burned, increasing the likelihood of weight gain.
- Environment: Limited access to safe areas for exercise, lack of affordable healthy foods, oversized food portions, and exposure to advertising for unhealthy foods all influence obesity risk.
- Genetics: Genetic factors can affect how the body regulates appetite, metabolism, and fat storage. Certain rare genetic disorders directly cause obesity, and genes also influence susceptibility to weight gain.
- Other influences: Age, hormonal changes, certain medical conditions (e.g., hypothyroidism, Cushing syndrome), medications, insufficient or poor-quality sleep, stress, gut microbiome composition, and social and economic factors can also contribute.
- Psychosocial factors: Stress and psychological well-being impact eating behaviors, often leading to increased consumption of high-calorie comfort foods.
Overall, obesity is a complex, multifactorial condition influenced by a combination of lifestyle, genetic, environmental, medical, and social factors. The global rise in obesity is linked to widespread obesogenic environments that promote excess calorie intake and reduce physical activity opportunities.
