In the majority of people, 'that is the right thing to think', eat properly and
get excercise, it's only a very few people who are very heavy because of desease.
We are not talking of disease here, talloola. Many times there is an underlying cause for obesity, and it has nothing to do with disease. Many times there are emotional problems associated with obesity. The boy may be bullied at school, or may be abused by his father, that is why he overeats. The woman may have low self esteem, may be abused by her husband, that is why she overeats. The man may be full of anger. Anger towards his boss, towards the precarious financial situation, marital problems etc. That is why he may overeat.
There can be many underlying cause of obesity. Unless these are treated, obesity will not be cured. Now, it may be that in some cases, there is just overeating, there no underlying cause for it. In such instances, no doubt the advice of eat right, exercise etc. will work. But in many instances, where there is an underlying problem, just lecturing a person as to how he should go about reducing the weight will be useless.