How to train for a marathon without losing muscle

We don't blame you for thinking you'll lose all your muscle if you train for a marathon. Long-distance runners are traditionally thin. And surely someone logging dozens of miles each week can't break free from the gawky, sinewed body of a marathoner. It's inevitable. Or is it?

Seth Gottesdiener ACE-certified LA-based celebrity trainer lends a few tips for keeping your size while building up your cardiovascular fitness (and some really great calves).

1. Carb up

"You're going to need more than your normal amount of carbs, especially on long run days," says Gottesdiener. "Be smart about it, and eat dense carbs when possible—such as whole grain and vegetable pasta, rice, oatmeal, and sweet potatoes. It may feel uncomfortable at first, but think of carbs as your fuel source. When you're running on empty, you're only taking a toll on your body."

2. Log it

"If you're shedding pounds and size with your running regimen, it may be time to write it down," Gottesdiener says. "The only way you really know if your staying on track is if you track what you're putting into your body. Try apps like MyFitnessPal or MyPlate. It's not unheard of for an active man to be consuming upwards of 2,500 calories a day and try to make at least 50% of that carbs."

3. Be consistent

"Have a schedule with your runs and make sure you're increasing your miles as well as your calories," Gottesdiener recommends. Getting on a solid sleep cycle is also important. That's when your body can truly only repair itself."

4. Don't skip the gym

"Weight training is one of the most important components of maintaining strength gains as well as keeping size on," Gottesdiener adds. "You knew that training for a race was going to require additional effort, so don't cut corners now. Along with being consistent in your running schedule, be consistent with your training, too. Try to dedicate at least three days out of the week to weight training."