Hello, eating oatmeal in the morning can lose weight, but the most important thing to lose weight is to participate in aerobic exercise, not diet. You eat oatmeal in the morning is no problem, lunch normal meal is no problem, is the evening alone to eat fruit is not enough, you are now 18 years old, but also the body development and maturity of the critical period, can not be in order to lose weight, too strict control of body weight, I recommend that you still eat a normal meal in the evening, eat a 7 into full. Then, it is best to do half an hour of aerobic exercise every day, such as jogging, jumping aerobics and so on, if you can't stick to it, take a walk for 1 hour after dinner. This persists for 2 months, you will see the results.