You have a faster metabolism. BUT do NOT focus just on the weight. You may LOOK thinner, but your body fat content, cholesterol level, and sugar could be high, given by what you just told us you ate. Also, what about your parents or grandparents? If they are thin, chances are you may STAY thin. BUT keep eating like that, and not only will you get fat in your twenties, your heart and kidneys won't make it without medication. My father is 80 years old and is NOT on any medication, does NOT have any vision or lung or other health issues, because he lived right and took care of himself in his prime. Always remember, the surface may look great, but the foundation will crack if not taken care of properly! Eating properly and exercise are vital for EVERYONE!