Some quotes from the article:
- Our bodies seem to adjust to prolonged, repeated physical exertion and its energy demands by burning fewer — instead of more — calories over the course of the day, even if our exertions continue at the same level, according to a surprising new study of energy expenditure conducted during a 20-week running race across the United States
- The study is among the first to quantify the upper limits of human daily energy expenditure and endurance, whether someone is running across the country, competing in the Tour de France or pregnant
- a small but growing body of research suggests there are limits. A 2012 study of energy expenditure among modern hunter-gatherers, for instance, found that despite being in motion almost all day, the tribespeople burned about the same number of daily calories as those of us who sit behind desks all day. In effect, the tribespeople’s bodies seemed to have found ways to reduce their overall daily energy expenditure, even as they continued to move.
- The changes in the runners’ energy expenditures were striking. In their first week of repeated marathons, the runners burned about 6,200 calories a day on average, a steep increase over their typical energy expenditure from the week before — and about what would be expected, based on their new level of activity
- But 20 weeks later, although they were running just as much and at about the same pace, the racers had lost little body weight, and were expending about 600 fewer calories each day on average than they did in the first week.
- By the end of the event, the researchers calculated that the runners were expending about two and a half times their resting metabolic rate each day, a notable decline from the early days of the event, when they were burning at least three and a half times their resting rate.
- The researchers also examined past studies of overeating, in which people gorged on food to see how much weight they gained and how quickly, and found that most of them added pounds at a rate that suggested they could absorb about two and a half times their basic caloric needs. That is, participants might swallow more calories, but their bodies could not process anything beyond that limit.
5 years