Man loses weight eating nothing but a certain food for 25 days — and paid a price

A New Jersey man ate nothing but certain foods from a fast-casual chain for 25 days — an experiment that left him nine pounds lighter and craving a slice of pizza.

Tim Donahue, a 27-year-old Hoboken resident who works in advertising in New York City, documented his challenge as a modern-day spin on Morgan Spurlock's 2004 documentary "Super Size Me," he told Fox News Digital.

But instead of eating McDonald's for a month, Donahue wanted to see what would happen if he exclusively ate at a chain on the opposite end of the fast-food spectrum.

AMERICA'S FAVORITE FAST-FOOD CHAIN NAMED: MCDONALD'S WINS HEARTS BUT NOT BEST BURGER, SURVEY SAYS "I think it felt the furthest possible opposite of McDonald's," Donahue said of choosing Sweetgreen.

The idea also came from watching his health-conscious co-workers routinely order Sweetgreen for lunch while he showed up with fast food .

"Everyone inside my office is very healthy, and they were getting Sweetgreen bowls every single day for lunch ," Donahue said.

"I myself would go pick up a fast-food burger and everyone would razz and make fun of me." Donahue originally intended to make his experiment last for 30 days, but there was a practical problem.

EATING 5 FRUITS AND VEGETABLES A DAY MAY NOT BE ENOUGH FOR HEART HEALTH, STUDY FINDS "I wanted to do 30, but if you try to look at your calendar and try to fit [it into] any 30-day window, there was always a wedding, a work trip, a reason why I couldn't do 30," he said.

"I said, 'You know what, it's either going to get done with 25 days or I'm never going to it done.'" His primary rule was simple: Whatever he consumed had to be available on Sweetgreen's menu, although he made an exception for black coffee .

And while Sweetgreen offers more than salads , Donahue tried to keep the experiment centered on its bowls.

By the third day, he said, there was little chance of turning back.

Donahue didn't begin the challenge expecting to lose weight , but by the end, the number on his scale had dropped by about 9 pounds.

He also found a clear favorite on the menu.

AMERICA'S LATE-NIGHT FAST-FOOD CULTURE MAY BE MAKING A COMEBACK — HERE'S WHY "I was rocking with the hot honey chicken bowl," he said.