Walk Fast? Good News—You're More Likely to Live Longer

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People who walk faster are more likely to live longer regardless of their weight. That's according to a study scientists say suggests fitness levels might be a better indicator of health than an individual's body mass index (BMI).

Researchers in the U.K. looked at data on 474,919 people who took part in the U.K. Biobank study between March 13, 2006, and January 31, 2016. The participants answered whether their usual walking pace was slow, steady/average or brisk. Researchers also measured factors including the participants' BMI (calculated by dividing an adult's weight in kilograms by their height in meters squared), their waist circumference, and body-fat percentage. On average, the participants were 58.2 years old and had a BMI of 26.7, landing them in the overweight category.

Participants who said they walked briskly had longer life expectancies than the others regardless of their BMI, at 86.7 to 87.8 years for women and 85.2 to 86.8 years for men. Meanwhile, those who walked slowly had shorter life expectancies, particularly those who said they moved slowly and had a BMI of less than 20, even though this was in the healthy range. Women in this group had an average life expectancy of 72.4 years, dropping to 64.8 years for men.

The authors of the study published in the journal Mayo Clinic Proceedings concluded: "Brisk walkers were found to have longer life expectancies, which was constant across different levels and indices of adiposity." Adiposity means being severely or morbidly overweight.

But more research must be done to look at whether the "high-risk" slowest paced low BMI group could improve their life expectancies by boosting their fitness, and whether walking pace could predict an individual's risk of disease, the authors noted.

Tom Yates, a lead author of the study and professor of physical activity, sedentary behavior and health at the University of Leicester, told Newsweek scientists have extensively investigated the role of excess body weight on a person's life expectancy over the past few decades. Studies from several countries have shown the risk of an overweight or obese person dying is lower if their fitness is higher.

"Most of these studies reported the beneficial effect of fitness in terms of relative risk reduction, for example 20 percent reduction of risk of death. Relative estimates, though, are difficult to interpret," he said.

To answer the "fit vs fat" question, the team opted for walking pace because it is a "good measure of general fitness and overall physical function," according to Yates.

The team were surprised that the lowest life expectancy was seen in those who were underweight with a slow walking pace. "This is in contrast to assumption that is often made that obesity confers the most risk," said Yates. "In fact, many other studies have also reported an elevated risk of mortality in those who are underweight, although ours is the first to investigate this in relation to walking pace."

However, he cautioned as the study was observational it didn't show causation between walking and life expectancy.

"While there are likely to be multiple factors contributing to the strength of our findings, it is well established that increasing your fitness is one of the best things you can do for your health. Increasing your walking pace in everyday life is a good way to increase fitness levels, particularly in those who are slow walkers," said Yates.

"Therefore, a key message is that people should be conscious of their walking pace, and slow walkers should try and walk faster."

The work is the latest to call into question whether BMI is the most accurate measure of an individual's health. Last year, a separate team of scientists argued that measuring what is known as the metabolome could be more precise.

This article has been updated with comment from Tom Yates.