Once we realize that obesity is (by and large) a modern lifestyle disease caused by needless stress and a diet consisting of mostly fake food perhaps we'll return to eating a whole food diet consisting of real food?
e.g. margarine (which has color added to it to make it look yellow, otherwise it'd be gray) is NOT a healthy alternative to butter.
the paleo diet is a growing diet/lifestyle based on eating real foods. If anything else its very interesting to read about. http://freetheanimal.com/ancestral-life-way is a great blog for anyone interested.
The general consensus though is to avoid processed foods and stick to whole foods. A big one is to eat animal fat instead of industrially produced vegetable and seed oils.
Also, limit carbohydrate intake (ideally eating only fruit and vegetables).
e.g. margarine (which has color added to it to make it look yellow, otherwise it'd be gray) is NOT a healthy alternative to butter.