Left, Arya Farzin, co-founder of the Heat Running app, before he lost weight. Right, Farzin after losing 200 pounds. (Arya Farzin)

Arya Farzin used to be big. Now he just dreams big.

The 28-year-old Bethesda resident, who lost 200 pounds several years ago and went on to become a personal trainer, is trying to “do something great for the fitness industry.” To that end, he and a partner have created a free mobile app called Heat Running, which aims to turn monotonous exercise into a fun, rewarding contest.

The app puts users into a race that they can see on their iPhones (there’s no Android version yet), “a virtual Mario Kart kind of thing,” as Farzin put it, referring to the popular video game. Runners are represented by dots, and although participants aren’t actually racing at the same time — the app takes users’ recent runs and their times to plot progress around a track — it looks like they are, and the effort required to overtake a dot in front of yours is very real, indeed.

The name Heat Running refers to racing heats, and participants can get placed into increasingly challenging groups of 10 by continuing to push themselves to run faster in their chosen distances. The idea for the app is derived from the many long, lonely miles Farzin logged on his quest to transform himself.

He grew up in the Washington area as “a very large kid who turned into an obese teenager.” During his sophomore year at Saint Joseph’s University in Philadelphia, Farzin stood 5-foot-11 and weighed 365 pounds; he had trouble walking up stairs, suffered from sleep apnea and disturbing heartbeat irregularities, and doctors were telling him he was well on his way to full-blown diabetes.

Heat Running aims to turn monotonous exercise into a fun, rewarding contest. (Arya Farzin/Heat Running)

During that Christmas break — when Farzin was unable to put on an oversize sweater he had received as a gift — he was approached by an uncle who had some experience with weight loss and suggested that the young man come spend the summer with him in Harrisburg, Pa. Farzin, who had been on a Jenny Craig program as a 14-year-old and had tried “like a hundredtimes” to lose weight, decided that he didn’t want to wait even that long. So he moved to his uncle’s house and transferred to a nearby community college.

Starting with 30-minute walks on a treadmill, which left him “dripping with sweat,” Farzin was ecstatic when he was eventually able to run for five straight minutes. When three weeks of regular workouts helped shed 20 pounds, he felt “home free,” knowing that there was no going back (in a figurative sense — he did return to the Washington region after four “isolated” months in Harrisburg).

Ultimately, it took two years for Farzin to complete his dramatic weight-loss journey. At one point he dropped to just 150 pounds, a swing in the other direction he concedes wasn’t ideal. He worked up to several miles per run and was ligting weights both to increase his metabolism and to ensure that, once the fat was gone, his “skin could wrap around” his muscles and not be “saggy.”

Farzin developed an eating regimen based on small meals every three hours, preferring “complex carbohydrates, lean proteins and healthy fats,” while keeping insulin levels low and steady. However, he had lost the first 100 pounds or so while using Nutrisystem, and when that company awarded him a substantial sum of money for being one of its winners in a weight-loss promotion, Farzin could focus on creating his app.

He had found amazing success with running, but he also found it “very difficult — very boring” at times. “I would oftentimes find myself pretending I was racing or running in the NFL,” Farzin said. “Just kind of putting myself in these scenarios to help me get through these long runs.”

Heat Running is something Farzin said he wished he had had because of its visible competition with others, making the whole experience more compelling. In that way, it differs from other running apps, such as Strava, that challenge users to beat other users’ best times, not necessarily beat them head-to-head in real time.

One of Heat Running’s big fans is Lauren Pierce, a 24-year-old graduate student at the University of Arizona. A former cross-country athlete in high school and current coach of high school distance runners, she enjoys marathons and triathlons, and she credits the app with helping her “become a faster runner.”

“It puts you in that [competitive] mind-set, which is really neat,” Pierce said.

She likes the app so much that she has taken an uncompensated position in which she provides feedback to its developers and tests new features. As an educational psychology student focusing on motivation during goal-attainment scenarios, she said, she had an academic’s analysis of how Heat Running can be effective.

“It’s kind of focused on this whole idea of ‘small wins,’ which is really powerful,” Pierce said. “So when you’re looking at a regular running pattern, you don’t have all of these different motivational encouragements and positive reinforcers that you’re getting when you’re using this app. . . . There are kind of small ways that you’re achieving your goals while you’re on this major running path.”

When I tried Heat Running, I found it enjoyable, although not without some drawbacks. Not every runner is going to want to glance at their phone a lot. An armband helps, but I found it sometimes difficult to discern the dots or my pace amid the glare of sunlight. Pierce told me that instead of looking at her phone, she listens to the app’s audio cues.

While some other running apps offer a lot of information, including heart rate and the number of calories burned, Heat Running provides only your overall times and race splits, as well as where you finished. (Pierce said she also runs with a Garmin device.) Farzin told me that he and his business partner, Joseph Phillips, also a personal trainer, “wanted to make it as simple as possible.” They plan to add more features in future versions. The next one of those is set to launch this month.

“Eventually, we want to be that app [that provides all the information runners want], but right now, I think we’re a complement to those apps,” Farzin said, adding that he and Phillips are seeking investors. But even if he is in the initial stages of a lengthy, challenging project, his history says that it would be foolish to bet against Farzin emerging in great shape.

Also at washingtonpost.com Read past MisFits columns at washingtonpost.com/wellness . There, you can subscribe to the Lean & Fit newsletter to get health news e-mailed to you every Wednesday.