The secret to my Mr Universe title? Potatoes and porridge

He trained hard and followed the high protein, low carbohydrate diet favoured by many bodybuilders wanting to gain muscle.

But the father-of-two from Fife felt tired all the time, his muscles looked "flat" - and he still hadn't achieved his dream of winning a Mr Universe title.

It was only when a new coach suggested he ditch his strict diet that he finally took the coveted Mr Universe Masters Over 45 crown.

She told him to eat sweet potatoes, white potatoes, grapes and porridge as well as his usual chicken and broccoli.

The 52-year-old was initially sceptical but so desperate to win the title, he told BBC Scotland News he was willing to try anything.

"At first when I started eating a lot more food and carbs I felt in a lot of pain because my body wasn't used to it as I had been dieting on very little food for so long," he said.

"In the past on my high protein diet I had felt tired a lot.

"But suddenly on this high carb diet I had all this energy so I could train for longer and harder and I felt stronger.

"Then I noticed my muscles looked bigger and fuller and harder, I just couldn't believe it."

A health and nutrition expert from the University of Edinburgh, Prof Lindsay Jaacks, said carbohydrates were of "critical" importance for exercise.

When he changed his diet, Mark, who is 5ft8in, increased his calorie intake from 2,500 to 5,800 per day.

His stage weight rose from 83kg (12.8 stones) to 90kg (14.1 stones).

And in Bradford in November, he took the National Amateur Body-Builders' Association's Mr Universe title he had dreamed of for decades.

Hollywood actor Arnold Schwarzenegger won the overall Mr Universe title four times in the 1960s and 70s.

"I had 10 Scotland titles and had all the Mr Scotland titles but I couldn't progress any further at British level as I wasn't big enough or hard enough until I met my coach Vicky and she introduced carbs into my diet," Mark said.

"I just can't thank her enough.

"People don't believe they need carbs for bodybuilding but this is the most successful I've ever been. I wish I had known sooner."

In addition to taking the Mr Universe title, he has dominated Masters competitions since changing his diet, winning Mr England, Mr United Kingdom, Mr Britain, and Mr World titles.

Mark, who runs Taylormade Gym and Fitness in Leven with his wife Anita and sons Bodhi and Dalton, said he started bodybuilding after working for a famous Scottish soft drinks firm.

"I started working with Barrs Irn Bru when I was 16, I was lifting lots of heavy crates and was developing a bit of a muscular physique and getting really strong from lifting all the juice every day," he said.

"I walked past WH Smith one day and noticed a bodybuilding magazine. I saw the guy on the cover and thought: 'I want to be like him'.

"I started competing and came second, then the following year won the overall championships."

Prof Jaacks, of Global Health and Nutrition at the University of Edinburgh, said she welcomed Mark's new approach to eating.

"I am not at all surprised if he was restricting carbs in any way that he wasn't getting very far because carbs are absolutely the most important of the macros when it comes to thinking about exercise," she said.

"Carbohydrates are absolutely critical because that's what the brain and the muscles use for energy sources during exercise.

"You really need to have sufficient carbs if you are going to be exercising particularly at that kind of elite athlete level."

She added: "It is really great to debunk this idea of high protein diets because I think it's generally overstated.

"Even people who are going to the gym a couple of times a week are likely getting perfectly sufficient protein and don't need to do anything in terms of increasing protein through taking supplements.

"There is a lot of public emphasis on protein and bodybuilding and taking the supplements and protein shakes but really it's not required for most people even people who are going to the gym a couple of times a day.

"Athletic associations now also emphasise actually a food first approach to getting protein rather than supplements and there are other nutrients in food itself that are good for health.

"So my recommendation is to try to get what you need from food and I think most people can do that in their usual diets."

Vicky McCann, chairwoman of the British Natural Bodybuilding Federation who encouraged Mark to eat carbohydrates, said: "Bodybuilders will eat slightly elevated protein from your average person because they need muscle growth however the way I train my athletes is that we have a much higher percentage of carbohydrates than protein because carbohydrates are muscle sparing.

"When your body is low in energy if it's lacking carbohydrates it will use protein as a source of energy so it means you are actually using your protein as a source of energy rather than a source of growth which is not what you are looking for as a bodybuilder."

She added: "Keeping the carbohydrates high through a diet works. It doesn't work very well for sedentary people but if you are training hard you do need carbohydrates."

Mark said: "I got ripped with carbs. I'm delighted and wouldn't go back to a high protein diet."

-bbc