Middle Age Spread...Watcha Gonna Do?

Thanks for all the suggestions! I was in great shape most of my life, so I just can't stand seeing any flab. Guess I'm trying to postpone the inevitable.

The working out isn't a problem. I'm sure I can suck it up and do the workouts. I was a long-distance runner most of my life. Very lean. The problem is that at 51 years old, I just can't eat like I have all my life. Doing all that running, I could always eat whatever I wanted when I wanted, and as much of it as I wanted. Not eating all day and then having a big bag of Doritos and a few beers can no longer pass for dinner without getting myself into weight trouble. I LOVE carbohydrates--pasta, potatoes, rice--but now I'm told that's the worst thing for me.

My biggest challenge is going to be diet.