A Bethesda native, Roll, 46, is one of only two people to complete five Ironman triathlons on five Hawaiian islands in under a week, and has been named one of the "25 Fittest Men in the World" by Men's Fitness. Although a California transplant, Roll returns to the District this week for DC VegFest, which celebrates the vegan lifestyle.

How did you get into such intense shape?

I had been a swimmer growing up in D.C. and later on at Stanford University. When you were swimming four hours a day as a kid, it was "how many calories can I put down my throat?" When the swimming career ends, the appetite for fast-food unfortunately keeps up with you. Around 40, I was sluggish and depressed, and I had a scary moment walking up the stairs to go to bed one night, where I doubled over to catch my breath and thought I was going to have a heart attack. It was scary, but I knew I wanted to make a change.

What's a good first step for someone in mid-life who isn't sure how to get started?

It's never too late. Little baby actions can build into mountains. First, eat more plants. We're sort of conditioned to think if you eat plants, you're a wuss. It makes no sense. A plant-based diet revitalized my body in a way I never thought. I haven't felt that good in 20 years.

What's your favorite leg of the triathlon?

Ask me on any different day and I'll give you a different answer. If I start training on my bike too much, I miss running or swimming.

Which D.C. routes are you looking forward to hitting this week?

My parents live in Georgetown, so I run across the bridge to Roosevelt Island and back. I want to get out to Rock Creek Park and do runs through the Mall, too.