Katharine Merry, the British winner of the bronze medal in the Sydney Olympics in 2000, had retired from sports two years ago.
But she was not prepared for the results of a binge drinking experiment she took part recently.
She grew two inches fatter, suffered skin problems, felt weak, lethargic and suffered a lack of appetite.
And she even needed a five-day course of antibiotics at one point, when her system began to collapse under the strain of the endless alcohol, and the trial had to be suspended until she recovered enough to see it through.
Previously she would not let a drop of alcohol pass her lips. But as part of the experiment, she had to she had to drink 60 units of alcohol for the programme over the fortnight - a common total among binge-drinking women.
That amount of wine contains 4,500 calories and is equivalent to 600ml of pure alcohol.
The runner also had to put her usual fitness regime on hold and restrict her exercise to just 5,000 steps a day.
"That much alcohol in just one sitting tipped my body over the edge and set a pattern for the two weeks," said Miss Merry, 33, who took part in the trial for a television documentary to be screened this week, reports Daily Mail.
"I had to go onto antibiotics because it was a massive shock to the system. It was a horrendous experience. It just knocked me for six.
"Hopefully the results of the experiment will be a lesson and a wake-up call to girls and young women who drink too much."
Merry was given the all-clear by her GP before she began the fortnight's binge-drinking and underwent a series of fitness tests to compare her state at the end.
On day one, she drank her prescribed two bottles of wine but suffered a restless night, and two days later she was still complaining of muscle pain, lethargy and lack of appetite.
But just four days into her challenge, she became ill with flu-like symptoms and had to be prescribed penicillin.
After she recovered to continue, she experienced her first crippling hangover and complained of a stomach "like a washing machine."
By the end of the fortnight, Merry noticed that she lacked patience, she was grumpy, her skin was bad and, worst of all, she was two inches fatter around her waist.
She said she could not understand why so many women drink large amounts at once and said she hoped she had set an example that others would heed.
"There is such serious issue with binge-drinking in this country, particularly young females," she said.
"These girls will hopefully watch the programme and realise how much damage alcohol can do to them."
Merry is now a mentor with UK Athletics for promising young athletes, encouraging them to lead healthy and disciplined lifestyles.