Carbs in diet. The diet of most Indians has more carbs than most other diets.
so in other words, way too much.
Fundamentally its a sedentary lifestyle that's incompatible with these foods. They are not evil; they're inappropriate for the American level of activity (taking vehicles everywhere; sitting all day; watching TV in the evenings). Indians come to America begin to do these things, and begin to have problems. No surprise.