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.

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"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.

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"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.

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"I was rocking with the hot honey chicken bowl," he said. "I was getting that all the time."

Donahue said the variety made eating from the same restaurant for nearly a month easier than one might expect. The bigger challenge, he said, was arranging his life around the experiment.

"The most challenging aspect of the project was not the food, it was the logistics," he said.

Meals had to be planned around the store's operating hours. Going out with friends meant skipping drinks and potentially bringing a salad along. Even dates with his girlfriend took a back seat.

One thing Donahue doesn't recommend about his experiment today is the price tag.

"You can cook at home and make a salad at home and spend a significantly smaller amount of money," he said.

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Donahue said he offset some of the expense by deciding not to spend money on alcohol or other restaurant meals during the challenge. But, he admitted, it was a "very expensive" project.

"Out of pocket, this is not a sustainable thing to do over groceries," he said.

Donahue also emphasized that Sweetgreen didn't pay him to conduct the experiment.

The company subsequently embraced his idea, Donahue said.

"His video inspired us to launch our own 30-day Sweetgreen challenge," Nicolas Jammet, Sweetgreen's co-founder and chief concept officer, told Fox News Digital. "We put out an open call for 30 participants to eat only Sweetgreen for 30 days and document how they feel throughout, and we already received hundreds of applications."

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After 25 days of salad bowls, Donahue headed to his favorite neighborhood pizzeria.

"A cheese pizza after a month of salads was incredibly well-deserved," he said.

There was just one problem.

The sudden return to heavier food didn't sit particularly well.

"It did make me feel quite sick because it's a shock to your system," Donahue said.

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Despite dropping weight and saying he experienced benefits, including more energy, Donahue isn't presenting his experiment as nutritional advice. 

He stressed that he isn't a doctor or nutritionist and didn't undertake the challenge to tell others how they should eat.

"The experiment was largely a fun filmmaking journey for me," he said. "I would never prescribe this to someone."