Jockey Sir Tony McCoy has put on two stone since he retired and has admitted eating "whole packets" of biscuits while watching TV at night.
The 42-year-old, who remains the most successful jump jockey of all time, bowed out of the sport in April 2015.
He spent decades dieting to keep trim for races and once said his Christmas dinner consisted of just 597 calories.
He now confesses to a weakness for chocolate biscuits but said a recent health check has made him rethink.
"There's nights I would eat the whole packet... it is not something I am proud of," McCoy said.
"For someone that had pretty good willpower it is not anywhere near as good as it used to be."
McCoy, from Moneyglass, County Antrim, was renowned for his determination and dedication over the course of his record-breaking career.
He won more than 4,000 races, and was crowned champion jockey 20 years in a row.
Keeping hold of that crown involved keeping his body weight well below what would be considered average for a man of his height - 5ft 10in (1.8m)
He maintained a thin frame of about 10 st 3lbs (65kg) with a punishing regime of meagre portions - often missing dinner three nights a week - and hot baths to sweat off the pounds.
Life has been sweeter since he retired, but McCoy will now revert to watching his diet after a recent health check warned of the risks of high cholesterol and blood sugar.
"When I was racing I was unhealthy looking," he said.
"Everybody tells me now I am healthy looking but yet there are things I need to keep an eye on like my cholesterol, the possibility of diabetes."
Back in 2010, his low-calorie Christmas dinner consisted of three thinly sliced pieces of turkey breast, a spoonful of cabbage, three Brussels sprouts, a splash of gravy and a small lemonade.
"I never mind having a frugal Christmas dinner as I'm always looking forward to some great rides on Boxing Day," he said at the time.
"What I do enjoy is seeing Mick Fitzgerald and Carl Llewellyn loosening their belts before they struggle home. I just can't imagine bursting out of my clothes like those two do."
The retired champion may have needed to pile on a few pounds, but McCoy now intends to monitor his food intake as "prevention is so much better than any cure".
"I spent all my life dieting but it is something I actually do need," he said.
"Because my body was so used to that I cannot really let my lifestyle change too much. I am two stone heavier than I was a year and a half ago."