Well today will be my first day back in a gym since highschool, (almost 3 years) Right now i weigh 280. I want to lose at least 20lbs by my 20th birthday(4 months away). I have cut down on the amount of food that i eat starting last month.
Breakfast- Ovaltine and a vitamin
Lunch- (wendys) Chicken Nuggets, Chili, and a Diet Coke
Dinner-Salad, Either Chicken or Beef

I will work out Monday, Tuesday, Thursday, Friday, Saturday(maybe)

Monday/Thurdsay-Bench, Closegrip, Curls, and Shoulders, then Cardio
Tuesday/Friday- Squat, Leg press, Leg Curls/extensions
Saturday(up for adjustment)-Cardio(running...etc)

At the rate i will be going i only need to lose 5lbs a month to meet my goal...Am i underestimating the amount of weight i could lose? Should I adjust my regimen? If i stick with this goal how much weight is possible for me to lose total?