Q: If I eat 2500 calories where 35% of the calories are from junk food and change my diet so that I'm still eating 2500 calories but only 10% of the calories are from junk food will I lose weight? I know that my cholesterol level will go down and my overal health will be better from the second diet.

A: Yes, if you replace that junk food with a balanced nutrition of meats/fish/poultry/eggs/cottage cheese, legumes, whole grains, veggies, fruits, nuts and olive oil (i.e. good stuff) then you will lose some weight just from that change. However it will not be a very significant weight loss and it will likely stop after a month or two as your body adjusts to the new diet. For more dramatic results I would definitely recommend taking up weight training and also perhaps slightly cutting down the over all calories to 2000-2200 per day (in addition to eating better foods as you mentioned, of course). However even just the dietary change you mentioned is something that you should certainly do, both for fat loss and for your overall health!