Low/med carb, high protein, med fat. All the same stuff I've said before for abs - you can do no ab work and have a sweet 6pack - if there's no fat covering them. You can also have amazing abs covered by fat. Hot tip (and generalisation)- most girls aren't actually impressed by a 6pack and prefer a 'manly' physique with a bit more thickness and enough body fat so that it 'doesn't feel like they are cuddling a rock'. You can't bloody win.
Anyway - get stuck into all the stuff I've said before, chinups, pushups, squats, deadlifts, complex core work. (In many variations). Plus sprints 2-3 x week. Compound resistance work, sprints, with good diet = real changes in 4-8wks.
Most people will end up looking like how they live. Ex fatty who mainly just jogs? That's what you'll get. Ex fatty who does lots of intense resistance and sprint training with a high protein/low-med carb diet + MTB? You're going to see some changes....