Q. I am a marathon runner and can't seem to consume more calories than I burn. I currently am a size zero and am worried that I am getting too thin. I do feel great and my doctor isn't worried about it.

Q. I am a marathon runner and can't seem to consume more calories than I burn. I currently am a size zero and am worried that I am getting too thin. I do feel great and my doctor isn't worried about it.

A. Let me guess your other problems: You can't figure out how to spend your millions and you have too many channels on your TV? But, seriously, if your doctor has given you a gold star and you're feeling groovy, you probably don't have to sweat this. As long as you're menstruating regularly and not consciously cutting calories, you can feel free to annoy the heck out of your friends.

But if you desperately want to fill out that cute size 2, here are some ideas. Monique Ryan, a Chicago-based nutritionist and the author of "Sports Nutrition for Endurance Athletes" recommends matching your food intake to your training schedule. If you're planning an extra-long run or a grueling speed day, dump a double serving on your plate the night before. Better fueling may lead to better workouts, too. Immediately after you finish, Ryan recommends chugging a protein shake or a glass of chocolate milk. Then, enjoy a full meal within 21/2 hours.

Don't pig out now on doughnuts and fried chicken. Ryan promotes bigger portions of good-for-you cuisine, such as whole-grain pasta and brown rice. The Post's diet diva, Sally Squires, throws her weight behind snacking: "Add two handfuls of nuts a day, and over the course of a week that's three-quarters of a pound of body weight," she notes. You can also up your calorie intake by flouting the usual rules and opting for larger portions of protein (such as a thicker slab of salmon), adding extra drizzles of olive oil and filling your glass with 100 percent fruit juice. Because liquid is less filling, you can sneak more calories into your body if you drink them.

Looking for more guidance? Sally's a fan of "Nancy Clark's Sports Nutrition Guidebook." You could also peek at "Nancy Clark's Food Guide for Marathoners."