Last August, I signed up to run my first marathon. Tackling 26.2 miles was a major life goal for me, and I hoped that all of the training would help me maintain my Feel Great Weight or even help me lose a few pounds! But more than four months later, I'm surprised that I've actually gained weight.

Now, none of my jeans fit over my quads of steel. And my once-buff arms look like those of a Tyrannosaurus rex! Never in a million years did I think my body would change this way because of marathon training!

Last week, I chatted with my friend, Rachel, who is training for her first marathon as well. She runs her marathon a week before I run mine, so we're practically on the same training schedule. Not surprisingly, we had a lot to talk about! Rachel's been experiencing many of the same struggles, emotions, and unexpected weight gain because of marathon training. She is a registered dietitian and certified specialist in sports dietetics, so I picked her brain about what was happening to our bodies.


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A lot of people go into marathon training thinking that they'll lose weight and are surprised when their weight stays the same or even increases, according to Rachel. There are a few reasons why this may be happening. The most common is that novice endurance runners are prone to overestimating the amount of calories they can consume during training. As we know, eating calories above and beyond what we burn will lead to weight gain. Bingo!

At the beginning of my training, I didn't even notice that I had increased my calorie intake. I just figured all of the running I was doing allowed me to eat whatever I wanted. One night, after a 14-mile run, I downed three slices of pizza, three beers, a cupcake, and about a zillion potato chips! Obviously, I consumed way too many calories—and not very nutritious calories at that! In the past few weeks, however, I've stocked my kitchen with much healthier foods, so when the "post-run munchies" hit, I'm prepared with nutritious options. Of course, it's normal to feel hungry when training for a marathon, so now I think twice about which foods I put into my mouth and which ones work best for me.

Muscle gain is another factor that Rachel mentions. "As the strongest muscles in the legs, the quadriceps and hamstrings are integral to running," she says. "Endurance running increases muscle mass in these areas to help sustain longer distances out on the road. While runners may lose fat with training, muscle is heavier and balances out any weight loss that would have been visible on the scale."

A third reason has to do with the body's incredible ability to adapt. Rachel explains: "With endurance training, the body stores more carbohydrates in the muscles, making [energy] readily available during long runs." The body also requires extra water to break down these stored carbs, resulting in gained weight. Hearing Rachel explain all this makes me feel better, but it's still tough to not focus on the scale, especially when most of my pants barely fit! Still, I know that I will thank my quads of steel when they help me cross the finish line after running 26.2 miles!