If all i eat is oatmeal all day would i gain weight ?

Oatmeal diet: You might or might not gain weight, however this would be a very unhealthy diet. It is not recommended. Best to eat a variety of fresh fruits, vegetables, nuts, beans, lean chicken and fish.

Calories count: You would have to count all the calories you ingest and if they are about 1200per day, and you are very inactive you could gain weight. The more calories you eat and the less you burn off, the more weight you will gain.