A postman went to extreme measures to prove his point on the importance of exercise by eating nothing but McDonald's for weeks and losing more than 7kg.

Ryan Williams, 29, launched his fast food mission to disprove filmmaker Morgan Spurlock's famous Super Size Me documentary.

In 2004, the American filmmaker gorged on McDonald's for 30 days and gained 12kg, chomping through 5000 calories per day.

But Ryan from Cheltenham, Gloucestershire in the UK, pointed out that he was doing no exercise during the challenge, The Sun reports.

He also wanted to make the point that the amount of calories you eat is more important than what you eat. So Ryan set his own challenge, spending between $27-$36 each day for a month on McDonald's and made sure to eat everything on their menu at least once, as Spurlock did 14 years ago.

But the buff postie also spent an hour at the gym each morning during his challenge in October.

And he finished the month 7kg lighter than when he began, having lost just over two per cent of his body fat.

Ryan documented the challenge daily on his YouTube channel 'Ry', where he has built up a following of more than 1200 people who frequently watch him eating quirky things.

He said: "I've wanted to do this for a few years, but I never found the right time.

"But recently I saw an advert for 50 years of Big Mac, and it made me think that there's quite a lot of negative feeling towards McDonald's, with regards to it being unhealthy.

"Ever since I saw Super Size Me, I thought that the way he (Morgan Spurlock) did the experiment, was unfair.

"He ate 5000 calories a day and didn't do any exercise. I didn't feel like it was a surprise he became so unhealthy," he said.

"It's obvious that calories are quite important, but the average Joe doesn't always know how to balance the recommended calorie intake with staying in shape.

"I'm not suggesting that eating just McDonald's is a healthy way of living, but I wanted to show that it's purely a calorie game, as opposed to the types of food you eat."

But Ryan, who started the month weighing 89kg, said it was all about sticking within the recommended calorie intake and maintaining a frequent exercise program.

He began the month eating 2500 calories per day - the recommended calorie intake for a male adult - but dropped down to 2300 by the end of the second week.

And in the final two weeks of the challenge, he dropped his calories slightly further, depending on how his weight and body fat index was performing.

In the same format as the original program, he made it a rule to eat everything off the menu at least once - from Big Macs and McFlurrys to salad boxes and bags of fruit.

Ryan said: "Prior to the challenge I was probably in the worst state I'd been in in a few years.

"My diet wasn't great, I would eat a lot of food - about 5000 calories - in a day, lots of biscuits and junk food, and I wasn't going to the gym at all.

"Before that, for about 10 years, I was always very active and went to the gym four or five times a week.

"So for me, this challenge was partly about what I could do to help myself get back to that, while also having a bit of fun."

By the end of his challenge, Ryan was down to 82kg and had gone from 10.85 per cent body fat during a seven-site skinfold test, down to 7.59 per cent.

Ryan said he switched up his eating habits halfway through the month, going from eating three meals a day in the first 15 days, to consuming all his calories for the day in one go.

He said: "On a couple of days I would eat only one item off the menu - so, for instance, I would live on just Big Macs for a day, or just McFlurrys for a day."

"I just hope that people see this and see the lightheartedness in it, and learn to worry less about the types of food they eat."

This article originally appeared on The Sun and he been republished with permission.

What they said: Captains, coaches react to big deciders

Premium Content What they said: Captains, coaches react to big deciders

See what St Teresa’s and St John’s leaders said about the clash

Coast woman’s new lease on life after COVID-19 redundancy

Premium Content Coast woman’s new lease on life after COVID-19 redundancy

A Sunshine Coast woman who turned to her spiritual side in a surprising career...

Cleaner loads bra with doctors’ scripts to fuel drug habit

Premium Content Cleaner loads bra with doctors’ scripts to fuel drug habit

Dale Jessica Freeman sneaks doctors’ scripts to fuel drug addiction