I heard 1st level is getting you fit, if you are fit then you skip this level. If you are not, then diet time. Basically you will probably eat plain chicken breast and fruits and veggies (SNSD's diet). Don't starve yourself, if you do then your metabolism slows down, so when you actually eat you will gain more weight. From dancing practices, I'm sure you will lose weight easily. It's not hard to lose weight if you're willing to exercise and change your eating habits. Well it might be, but before you realize it as you get used to your training, you will be thin from continuously dancing. Yes, I have heard of water diet (you're most likely not going to go into water diet), and your body will only go into famine mode from just drinking water. So if you lost weight, when you eat, you will gain it all back. You're body will suck in every bits of calories you get when you eat. If you drink too much water, like excessive amount of water then it can cause a condition called hyponatremia which basically just means that you can excrete the extra water quickly causing your blood minderal content getting diluted and your sodium level will drop.