is food and nutrition course available?

Any community college will have low-level, basic nutrition classes. If you want to be a Dietitian, find a college near you and sign up (assuming you have the grades, but almost anyone can get into some college these days and anyone at all can go to community college.)

Dietitians do a LOT more than weight loss, though. That's just one little part of their job. They focus on food to help people be healthy and that includes people with bunches of different diets for bunches of medical reasons. They need to know what is right for different people and that varies in a big way.