It can, but it doesn鈥檛 have to.
If you鈥檙e looking at runners who dominate marathons such as Kenyans , you鈥檝e probably noticed that they鈥檙e very slim. Skeletal, even. pegged four-time Boston Marathon winner Robert Cheruiyot鈥檚 height and weight at 6-foot-2 and 143 pounds. Why so small? Because the 鈥渕ore you weigh, the harder you have to work to lift your body and the slower you will be,鈥 the article explains.
Often marathoners welcome the calorie incineration a high-mileage regimen creates as an opportunity to drop any unwanted weight, including excess muscle. But if you don鈥檛 want to shed your shredded six-pack or cut quads, consider this: you won鈥檛 if you eat enough.
鈥淐aloric intake must be matched to caloric expenditure,鈥 says , a certified sports dietician and nutrition consultant for the . 鈥淲hen that is accomplished, muscle mass can be maintained.鈥
She recommends that runners concerned about dropping weight get their resting metabolic rate professionally tested. That way, they鈥檒l know exactly how many calories they need to keep their weight stable.
And don鈥檛 gorge yourself on protein thinking it鈥檒l maintain your muscles. Antonucci recommends taking in 1.6 to 1.8 grams of protein per kilogram of body weight, but no more than two grams per kilogram per day. That鈥檚 about 109 to 122 grams per day for a 150-pound person, or 136 grams max. Above that, Antonucci says, 鈥渢hose are basically calories you鈥檙e wasting. Extra protein doesn鈥檛 do anything for you if it鈥檚 above and beyond what your body needs.鈥
So to recap: Make sure you鈥檙e taking in as many calories as you鈥檙e burning, and you should maintain your muscle mass. If you鈥檙e doing that, and your protein intake is above 2g/kg of body weight per day, cut it back to the recommended range, and replace the excess protein with carbs and fat.
Now go crush your next marathon (here鈥檚 a handy how-to guide), and be sure to flex for your finisher photo.