MODEL RELEASED. Consultation. General practice doctor consults with an obese man. A person is considered obese when their body weight is at least 20% more than the maximum desirable for their particular height. The cause of obesity is not always clear: some people simply eat too much while others become obese due to genetic factors, low metabolic rate or physical inactivity. The condition increases the risk of stroke, heart disease, diabetes, and aggravates osteoarthritis.