New York Times article - May 2014: Need to expend 2000 calories weekly in exercise:
Q: 1 have read and heard that a person should aim to expend 2,000 calories weekly in exercise for optimum health. Is there any basis at all for this notion?
The idea that we should burn at least 2,000 calories a week during exercise seems to have originated in data gathered decades ago as part of the Harvard Alumni Study. That study followed male Harvard graduates for as long as 50 years, tracking how they lived and died. One of the first publications based on the data, appearing in 1978, showed that the older alumni who expended less than 2,000 calories a week in exercise were at 64 percent higher risk of suffering a heart attack than those who burned 2,000 calories a week or more during exercise. It’s worth noting that the researchers’ definition of exercise in this study was generous, including climbing stairs and walking around the block, as well as playing sports or jogging.
Widely reported at the time, the 2,000-calorie guideline still gets bandied about today. But the current exercise guidelines from the federal government, based on a large body of recent scientific evidence, emphasize time, not calories, and recommend that healthy adults engage in 150 minutes per week of moderate-intensity exercise, such as brisk walking or cycling.
Adhering to these guidelines means that most of us would burn about 1,000 calories per week in planned exercise, said Michael J. Joyner, an exercise researcher at the Mayo Clinic. And with the stairs we climb and chores we do, we come closer to that 2,000 calorie a week number, he said.
But we don’t have to fret about actually reaching it. Meeting the current guidelines for 150 minutes or five brisk 30-minute walks per week is enough, he concluded. “The added health benefits start to level off after that.”