A New Jersey man spent 25 days eating exclusively from Sweetgreen, emerging about nine pounds lighter but ready for pizza and painfully aware of the financial and logistical costs. Tim Donahue, 27, documented the experiment while balancing work, relationships and the chain’s operating hours.

The Hoboken resident, who works in advertising in New York City, described the challenge as a modern day version of Morgan Spurlock’s 2004 documentary “Super Size Me.” Instead of spending a month eating McDonald’s, Donahue chose a chain he viewed as its opposite.

“I think it felt the furthest possible opposite of McDonald’s,” Donahue said. The idea was also inspired by his health conscious coworkers, who regularly ordered Sweetgreen for lunch while Donahue arrived with fast food.

Donahue said his coworkers would tease him when he picked up a fast food burger as they ate their bowls. Their contrasting lunch routines helped push him toward an experiment centered largely on Sweetgreen’s salads and bowls.

He initially planned to continue for 30 days, but weddings, work travel and other calendar commitments kept interfering with every possible monthlong window. Donahue ultimately decided that completing 25 days was better than allowing the idea to remain unfinished.

His main rule required everything he consumed to be available on the Sweetgreen menu, with one exception for black coffee. Although the chain sells more than salads, he tried to keep the project focused on its bowls.

By the third day, Donahue felt there was little chance he would abandon the challenge. He had not started the experiment expecting to lose weight, but his scale showed a decline of about nine pounds by the end.

One menu selection became a recurring favorite during the 25 days. “I was rocking with the hot honey chicken bowl,” he said. “I was getting that all the time.”

The restaurant’s variety made the eating portion of the challenge easier than Donahue had expected. The more punishing issue was organizing daily life around a single chain and making sure meals were available when he needed them.

“The most challenging aspect of the project was not the food , it was the logistics,” he said. Meals had to fit the stores’ operating hours, while outings with friends sometimes required him to skip drinks or bring a salad.

His social life also felt the strain, and dates with his girlfriend took a back seat during the experiment. The narrow dining rule meant ordinary plans had to be reconsidered around Sweetgreen access and menu availability.

Then came the bill. Donahue said preparing salads at home would cost significantly less, although he offset some of the expense by avoiding alcohol and meals at other restaurants throughout the challenge.

He nevertheless called the project “very expensive” and warned that paying for it personally was not a sustainable alternative to buying groceries. Donahue also emphasized that Sweetgreen did not pay him to undertake or document the experiment.

Sweetgreen later embraced the concept. Nicolas Jammet, Sweetgreen’s co-founder and chief concept officer, said Donahue’s video inspired the company to announce a separate challenge involving 30 people eating only Sweetgreen for 30 days.

“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,” Jammet said. The company’s challenge extended Donahue’s basic idea by five days.

When his own 25 days ended, Donahue went directly to his favorite neighborhood pizzeria. “A cheese pizza after a month of salads was incredibly well-deserved,” he said.

The celebration came with an unpleasant consequence. “It did make me feel quite sick because it's a shock to your system,” Donahue said of suddenly returning to heavier food after the challenge.

Despite losing about nine pounds and reporting benefits that included more energy, Donahue is not offering the experiment as dietary guidance. He stressed that he is neither a doctor nor a nutritionist and did not complete it to tell others what to eat.

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