Obesity is a condition resulting from accumulation of excess body fat in general; we say that a person is obese when their weight is 20% or more above the recommended weight for a man the same age, sex and size and bone structure.
Family factors are another interesting question, 80% of children from two obese parents are obese, 40% of children from a marriage when one partner is obese, suffers from this disease and only 10% of obese people when none of the parents. Some authors refer to this as a factor "gene", also controversial, as a practical ...