John Cisna from Iowa, US, lost nearly 40lbs (17kgs) during an experiment that saw him eat every meal at his local McDonald’s restaurant

A daring science teacher who survived on eating only McDonald’s meals for 90 days has shed nearly 40lbs.

John Cisna of Ankney, Iowa, ate three meals a day at his local store but made sure he conformed to strict nutritional requirements.

Cisna and his students used online nutritional information to construct a daily diet plan that exceeded no more than 2000 calories a day and included 45 minutes of exercise.

The unique experiment – reminiscent of the infamous 2004 documentary ‘Super Size Me’ – resulted in Cisna losing 37 pounds and saw his cholesterol drop considerably – from 249 to 170.

However, the science teacher did not just limit himself to salads and water.

Speaking to KCCI News, Cisna said: “I can eat any food at McDonald’s that I want, as long as I’m smart with the rest of the day and what I balance it out with.”

“I had the Big Macs, the quarter pounders with cheese. I had sundaes, I had ice cream cones.”

As well as significantly improving his health, the experiment did not cost Cisna a dime.