Let’s say you start drinking a soda from the school vending machine every day, taking in an additional 200 calories a day. at this rate, how long would it take you to gain one pound of body fat?

It would take 18 days, because it takes 3,500 calories to gain a pound, 3500/200 is 17.5, round that up to 18.

don't worry, but do consult a doctor.

explanation:

having a high metabolism at age 13 is not abnormal.   however, if you are concerned, do consult a doctor.   the doctor may identify a correctable issue, and then you'll have your answer.   in the meantime, there are a few steps you might consider.

first, reflect on just how much physical activity (work out and dancing) you are getting relative to your caloric intake.   keep in mind that if you are interested in gaining weight, you must have a higher caloric intake than output.   second, if eating robust healthy meals is not providing enough calories, you'll need to include high caloric, yet healthy, snacks.   i warn against using an over the counter high-calorie supplement (drink or food) until you have consulted a doctor.  

its c just did the test