John Cisna, a science teacher in Ankeny, Iowa, enlisted his students help him with an experiment: He wanted to see what would happen if he only ate McDonald's for three months.
Inspired by the film Super Size Me, Cisna planned to put together an amateur documentary about the process, KCCI reports.
Following a strict 2,000-calorie diet, Cisna had his students construct meals for him using McDonald's online nutritional information.
They also tried to stay close to the recommended dietary allowances for carbohydrates, fat, proteins, and cholesterol.
Cisna didn't heavily restrict himself; a typical breakfast would be two egg white McMuffins and a bowl of maple oatmeal, lunch would be salad, and dinner would be a value meal — like a cheeseburger and fries.
"So this isn't something where you say, 'Well, he went to McDonald's and he only had the salads,'" he said. "No, I had the Big Macs, the quarter pounders with cheese. I had sundaes, I had ice cream cones."
The owner of the local franchise was so interested in how the experiment would turn out that he agreed to provide the 90 days of meals to Cisna for free.
In addition to watching his caloric intake, Cisna also began walking 45 minutes a day.
Cisna admits that before the experiment, he didn't exercise or monitor his eating habits.
When the experiment was over, Cisna had lost 37 pounds and brought his cholesterol down to 170 from 249.
His low-density lipoprotein, known as "bad" cholesterol, also dropped from 173 to 113.
"I can eat any food at McDonald's I want as long as I'm smart for the rest of the day with what I balance it out with," Cisna said.