What are the causes of obesity?

Too many calories: Obesity is the result of intake (food) exceeding output(exercise). There are a few medical conditions that can cause obesity, such as untreated hypothyroidism, and prader willy syndrome. Some medications can also cause weight gain.

Many: Simple answer, too many calories. Long answer, complex disease process, with many alterations in hormones and neurotrasmitters, genetic component, behavioral component, vicious cycle with other comorbid conditions, ex, it can make sleep apnea worse, having sleep apnea often causes weight gain. Usual answer from health professionals, eat right and exercise is often not satisfying with good reason.