Double Olympic gold medallist and 2019 Oxford Cambridge Boat Race winner, James Cracknell just ran 100 miles in five days whilst only consuming water. 

Aged 46, Cracknell defied his age to become the oldest man to ever compete, and win, the Oxford Cambridge boat Race in 2019. According to his social media pages, Cracknell, now 48, took on this feat to prove that the body can be fuelled by fat alone. 

Photo Aged 46, Cracknell became the oldest man ever to win the Oxford Cambridge Boat Race. April 2019.

Credit Benedict Tufnell

Before beginning the challenge he wrote, ‘Why? The Dietary Guidelines advises 55% of our diet should be carbohydrate has no scientific basis. Society is eating too many carbs, as a result over 60% of the UK population is overweight. This project is aiming to prove the body can turn to fat to fuel itself efficiently.’

He was joined by a team of four doctors and three diabetic runners, including Steve Bennett, author of Fat and Furious, who mid-way through the five days, posted, “‘All 8 participants feeling great, but sore. Today’s route looks interesting, but we have broken the back of it / as we are ahead on miles. My glucose is in the same range as I would expect after a meal!! What science this is! #fasting’

Cracknell wrote, ‘2 days & 45miles done with zero calories. Metabolic testing shows no longer burning carbs but energy levels surprisingly good. 3 days left.’

After succesfully completing the event on friday, Cracknell wrote, ‘Just finished 5-day 100mile run. No calories in, just using fat reserves. Not recommended for high perf sport, last 5 days have shown that calories in v calories out is wrong approach.’

According to Runners World, Cracknell has told his followers he is hoping the challenge will ‘add to evidence that a low carb diet is an effective therapeutic treatment for diabetics and beneficial for pre-diabetics’.