Your body got weak and chubby all at once, what makes you think it can't get strong and lean at the same time as well? lol
What do you think would happen if you just ate steak, eggs, protein shakes, fruit and vegetables every day? Especially while lifting weights at least 5 days a week, and doing some cardiovascular exercise on a regular basis...
I don't think you should just start eating 4000 calories and trying to "bulk up" right now, no. But I think if you ate cleanly, with a ton of protein and enough carbs to fuel your training, you could reshape your body into something that can be built upon.
Something a lot of people don't acknowledge is that there's no such thing as a bodybuilder who is "out of shape". If you're out of shape, get in shape first (this does not mean "cut" or get super lean). Then pack on the muscle mass at full speed. That's just my opinion.