FILE PHOTO: A man exercises early in the morning along the Arabian Sea in Mumbai, India, December 21, 2017. REUTERS/Danish Siddiqui

LONDON (Reuters) - The world economy could be boosted by as much as $100 billion a year if employers successfully encouraged their staff to meet World Health Organization guidelines on exercise, according to an analysis of the economic impact of activity.

Adding an extra 15 minutes of daily walking, or jogging a steady one kilometer each day, would improve productivity and extend life expectancy - leading to more economic growth, the study by the health insurance group Vitality and the think tank RAND Europe found.

The economic boost would come from lower mortality rates - in other words keeping more people alive, working and contributing to the economy for longer, the study’s authors said, and from employees taking fewer days off sick.

Hans Pung, RAND Europe’s president, said the study highlighted “a significant relationship between inactivity and productivity loss” and should give policymakers and employers “new perspectives on how to enhance the productivity of their populations”.

The WHO recommends that all adults should take at least 150 minutes of moderate exercise, or 75 minutes of vigorous exercise, a week. In a study last year it found that around 40 percent of adults in the United States, 36 percent in Britain and 14 percent in China did too little exercise to stay healthy.

The RAND/Vitality study was based in part on data from about 120,000 people across seven countries. It then modeled and projected the potential economic benefits of increased physical activity globally and for 23 individual countries.

It found that if all adults aged between 18 and 64 walked 15 more minutes a day, it could increase world economic output by some $100 billion (£77 billion) year on year.

It also found that physically inactive 40-year-olds could increase their life expectancy, on average, by 3.2 years, by introducing 20 minutes of jogging a day.