Actually that is not as straight forward a question as you might think. When I trained it was stressed that there was no real evidence that obesity was an isolated risk factor. For many years this got lost and it was assumed that being fat meant automatically being unhealthy. More recently it has again been suggested that this is in fact not the case. If you take a normotensive,obese patient without diabetes and with a normal cholesterol who takes regular exercise he is not at great risk of disease. The problem is that most obese patients take little exercise, tend to have raised blood pressure, poorer cholesterol and are at high risk of developing diabetes.