Health Farm

-- The accepted wisdom that the harder and longer your workout, the more calories you burn makes perfect sense. However, new research suggests the tenet holds true only to a certain point.

Scientists studied six participants in a one-off foot race called Race Across USA, which involved running cross-country from California to Washington, D.C. – the equivalent of a marathon almost every day for about 20 weeks.

Over the first week of running, participants burned an average of 6,200 calories a day. However, as the event neared its end, the racers had lost little body weight and were burning about 600 fewer calories each day, despite maintaining a pace close to that which they ran in first week of the race.

The findings align with a 2012 study investigating the energy burn of modern hunter-gatherers, who, despite being on the move for most of the day, burned about the same number of daily calories as desk-bound office workers. Researchers concluded that the tribes-people’s bodies had found a way to reduce their overall daily energy expenditure, even as they continued to move.

Perhaps we’re hardwired to settle on a calorie burning sweet spot, so when food is scarce we’ve got enough fuel in the tank to keep going until we drag down the beast for the feast.

Scientists suggest this is why some people who train for endurance events gain weight.