Let's note immediately that this was not a Jennifer Capriati-style gesture. The nearest the 30-year-old Essex girl came to substance abuse involved the potato, and maybe summed up in the phrase "chips with everything".
But more profound shifts in attitude took place after Gunnell, defending her Olympic 400 metres hurdles title, had left the Atlanta track in tears - and a wheelchair - after breaking down with an Achilles tendon injury.
That public collapse brought to an end a two-year period of struggling with physical breakdown for the athlete who had completed a grand slam of Olympic, world, European and Commonwealth titles in 1994.
"The last four years have been like a big roller-coaster," Gunnell said. "After Atlanta I just wanted to get away from athletics. My first thoughts were, `I've had enough; I've had my day.'
"I was in a really rebellious state. I just wanted to rebel against everything I had done in the last 15 years."
So it was that jacket potatoes got the push. "I had a month of eating everything in sight," she said. "I ate a helluva lot of chips."
Normal life suddenly assumed enormous appeal. Gunnell bought a puppy, a chocolate-coloured labrador named Jessie. She began riding, a risk she would not previously have run, taking her husband John's horse, Corky, out for hacks on the Downs behind her home near Brighton.
However, what made the biggest difference as she re-evaluated her attitude to life was a visit to Angola in October last year, but when she accepted - as the Princess of Wales did more recently - an invitation from the Red Cross to meet victims of landmines.
"In other years I would probably have thought, `Oh no, I can't go down there. I might get ill.' But I wanted to go.
"These people are living in horrific conditions in a country that has been at war for 30 years, and yet they are still smiling and enjoying life. It certainly sorts your own life out. I realised I hadn't got any problems compared to these people."
The desire to return to competition she describes as a gradual feeling rather than a blinding realisation. But her positive feelings were confirmed during the new year's training break in Stellenbosch, South Africa, from which she returned on Monday.
This Sunday, she will compete in her first race since Atlanta when she takes part in a 400m at the Stuttgart indoor meeting.
"I want to do one more year," she said. "I didn't want my last race to be one where I was carried off the track."
Compared with this time last year, when she was recovering from an operation on her right Achilles tendon and weighed down with the burden of defending her Olympic title, she is in good shape. "I am much further on," she says. "Much more like my old self."
But not quite her old self. Indeed, she seems to accept that she may never be. "I've been told that there are weaknesses in my Achilles tendons after years of training," she said. "You have to expect that. But I've said that I don't want to go through another operation."
She is approaching her final year in a manner that you might describe as semi-detached.
"If I only do two or three indoor races, at least I'll have done something else," she said.
"I can't hide the fact that I will be nervous in Stuttgart. I'm hoping I'll come away from that track and think `Yeah, I still enjoy this. I want to carry on doing it.' But if at any point I think I'm not enjoying it I feel now I can call it a day."
Gunnell is deliberately not planning beyond March or April. "Right now I've got no confidence," she said. "I've got nothing to build on. The only way I can get back is by little building blocks."
If things go well for Gunnell in the next months, she may run the World Indoor Championships in Paris. A good performance there would encourage her to have one final fling at the World Championships where she would face, among others, the new Olympic champion and world record holder, Deon Hemmings of Jamaica."But I have not got my head around that yet," she said.
Formidable hurdles still lie ahead on Gunnell's last tour of duty. She is making no predictions, but she is back on jacket potatoes.