The idea of small meals is ideal, but just that someone your age must take more meals say at least 4-5 meals. Your ideal weight range should be between 64-74 kg, so you need not bother if you gain a little too. Your tummy is out because you are sitting about 80% of your day with no exercise. Resort to tummy tucks/ab exercise (please refer the Internet for correct method). Do not, I repeat do not, skip breakfast. It is what you need to keep your system alive and kicking through the day. I do agree with what your parents say - skipping meals will only release more acid and no food to work on will result in gas and acidity. Drink a minimum of 12 glasses of water, no matter what. Take fruits in mid morning and early evening - maybe you can carry an apple to college. Take something while you are tutoring. This is the right age for you to get into a regimen, be it study or food, after all health is important and you realise it and thats why you have visited this site!