argue the case in favour of either end of the day. But what about exercise's ability to kick start your metabolism? Isn't that a reason to drag yourself out of bed in the early hours? "When you exercise your metabolism does stay elevated for a period after that. But I would say that you get the same benefit whether [you exercise] in the morning or the evening," says Guelfi. A morning workout however might be more likely to "enhance other aspects of your life throughout the day, for example your mental awareness [and] your alertness". Guelfi was also a contributor on a recent study which looked at whether exercising in the morning or afternoon had any effect on how much healthy men ate throughout the day. "Whether they had exercised in the morning or the evening, their overall food intake throughout the day wasn't different," she says. "So you get more support for this notion that it probably doesn't matter what time you exercise." Exercise and heart attack risk Another common idea is that because heart attacks and other cardiac events occur more frequently in the morning, people who are at increased risk should exercise vigorously only in the afternoon. However in a 2007 scientific statement, the American Heart Association said cardiac events during exercise were relatively rare. Given that regular exercise reduces your overall risk of these events, it was probably more important to exercise at a convenient, rather than a specific, time of day, the statement said. And