The major physiologic contributor to overweight & obesity is longstanding positive energy balance (likely a combination of increased caloric consumption and lack of physical activity). While there may be genetic factors that contribute to its development, they are difficult to determine. In addition, a number of socioeconomic and other lifestyle behaviors are impossible to remove from the impact on overweight & obesity.
Accumulation of adipose tissue (storage of excess calories or lack of physical activity) increases fat mass and provides resistance to blood flow increasing blood pressure and resulting in a number of alterations to cardiac and vascular structure and function. In addition, fat accumulation in tissue reduces organ-specific efficiency and impairs function (e.g., cardiac, liver, muscle) and can contribute to the onset of other metabolic diseases. Hormone dysregulation can also contribute to overweight & obesity with obese individuals becoming leptin resistant and thus having impaired hunger/satiety signaling. In addition, overproduction of Ghrelin stimulates hunger and increases caloric intake.
In addition, it has been suggested that the set-point theory of weight control plays a significant role in overweight and obesity.
Pharmacological interventions are often used to alter appetite or sensations of satiety and typically have minimal to no effect on exercise. However, bariatric surgery that restricts stomach size or creates reductions in nutrient absorption, while effective, may lead to reduced energy for higher intensity exercise.