How long can i lose weight by not eating?

You need to eat: You need to eat at least 3 times a day. If you really exercise then need to eat more small meals per day, specially a good protein drink-smoothie 1 hr before and after exercise (to provide glycogen- energy and protein for muscle), and hydrate during exercise. Need health protein, fruits (carbohydrate), salads and a positve mental attitude.

You must eat : Eat foods that are nutrient dense (like meat, fish, poultry, eggs, cheese, low starch vegatables and water) avoid foods that are not nutrient dense (like starches and sugars, including fruit) nutrient dense foods will increase your basal metabolic rate. On the other hand, starches and sugars impair thyroid metabolism via affects on your liver (which helps activate thyroid hormone).