A diet is a pattern of eating behavior. People frequently refer to their diet when they are attempting to lose weight. A person who is dieting (attempting to lose weight) is "on a diet." "In diet" is grammatically incorrect.

If that diet has made you or the baby sick it can

No, the South Beach Diet is not effective when one is trying to lose actual fat. No diet can accomplish this actually. You can never actually lose fat, but you can shrink the fat cells.

Diet and exercise.

There is no proof that there is a natural diet pill. The best way to lose weight is to eat healthy and lose weight.