So much for training your body to rely less on carbs and more on fat for fuel in endurance training: new research shows a dramatically higher risk of premature death from low-carb diets including Atkins, paleo, and keto.

RELATED: Fat adaptation: what does it mean for runners?

Last week we reported on one elite endurance runner’s success with a very low-carbohydrate diet. Nikki Kimball of Bozeman, Montana, who has dominated women’s ultrarunning at various times, attributes not only her success in racing but her ability to manage her depression to a diet that includes a lot more cheeseburgers than quinoa salads.

Credit: With Food + Love

The reasons have to do with training the body to burn fat for fuel rather than carbohydrate, which is desirable for endurance training because the body can’t store as much carbohydrate as it can fat (which is why we must replenish carbs throughout and immediately after a long race). 

Running foods recovery

The research was presented earlier this week at the European Society of Cardiology Congress in Vienna. Scientists from Poland presented findings involving 25,000 Americans, with an average age of 41, who participated in the U.S. National Health and Nutrition Examination Survey between 1999 and 2010, and here’s what they found: during the six years following the survey, those who followed a low-carb diet had a 32 per cent higher likelihood of dying prematurely. When considering the data specifically for heart disease, the number jumped to 51 per cent. For cancer, 35 per cent. Scientists confirmed the findings by comparing them with other research studies, and found consistent results across the board.

The authors speculate that the reason for this may be the reduced fibre, vitamins and minerals from a diet containing few fruits and vegetables and more animal protein, which has been linked to heart disease and cancer.

There are some obvious issues with the research: first, it’s based on self-reported data. There’s no indication of uniformity in the standard for what exactly constitutes “low-carb.” Also, in the general population (i.e. non-runners), low-carb diets are adopted primarily for the purpose of weight loss, not fat adaptation, meaning many of the research subjects are likely overweight to begin with, which in itself carries some risk. 

There is also no indication of whether the data were corrected for such risk factors as smoking, a sedentary lifestyle, or mental illness, all of which may contribute to a higher risk of premature death. And the authors of the study readily admit that the numbers do not prove that low-carb diets cause premature death, and that further research is necessary. 

RELATED: The ketogenic diet: here’s the skinny for runners

Still, in terms of overall health, it seems safest to adhere to what we already know, which is that the safest diet for long-term health is likely one that includes an abundance of fruit and vegetables (which are excellent sources of fibre, vitamins and minerals), whole grains, lean meats and fish, and that minimizes added sugar and saturated fat. And we’ll just have to keep taking those gels, bagels and bananas at the race.

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