The relationship between psychology and heart disease is far more complex than Type A theory proposed. But in another sense, that short-fused workaholic guy was the originator of today's more sophisticated view.
Diets and dieting are not the solution to your stubborn weight problem. They are among the main causes. Learning how to eat well habitually, in a way that is more enjoyable than what you do now, is the solution -- and it is not just a matter of "willing" it.
Even Hippocrates hinted at this powerful connection when he said that he would rather know what sort of person has a disease than what sort of disease a person has. He also said that natural forces within us are the true healers of disease.