Which Comes First, Cardio or Weights_ - Alex Hutchinson [80]
Eating patterns can also influence these hormones. In a 2010 study, Greek researchers had volunteers eat identical bowls of ice cream in either 5 minutes or 30 minutes. (For the slow eaters, the researchers divided the ice cream into seven equal parts and fed it to the volunteers every five minutes, so that it wasn’t melted by the end of the half-hour.) In this case, although there was no difference in ghrelin levels, the researchers did observe significantly higher levels of peptide YY and glucagon-like peptide (two gut hormones that signal fullness) in the slow-eating group. This group also reported feeling more full.
Another long-standing staple of dietary wisdom is that you should eat frequently rather than cramming all your calories into three big meals. The idea is to prevent large hunger swings by keeping the levels of appetite-determining hormones in your gut relatively constant. But studies over the past half-century have reached conflicting conclusions about whether this actually works. Most recently, researchers at the University of Ottawa put 16 obese volunteers on diets with identical caloric deficits for eight weeks, publishing the results in the British Journal of Nutrition in 2010. Half of them ate three meals a day, while the other half ate three meals plus three snacks, with the total intake tailored so that each subject was burning 700 more calories than he or she consumed each day. By the end of the study, the subjects had lost an average of 4.7 percent of their starting weight, but there was no difference between the two groups. The researchers also measured the hourly fluctuations in ghrelin and peptide YY but didn’t find any significant differences between the two groups.
The University of Ottawa study suggests that snacking doesn’t have any miraculous appetite-reducing effects, but the subjects weren’t regular exercisers. If you do work out regularly, the rules are slightly different. It’s a good idea to eat something very soon after exercising (see Chapter 10)—it could be either a meal or a snack, depending on your schedule. This will help you recover from the workout, and there’s some evidence that it might help you avoid overeating later.
Will sitting too long at work counteract all my fitness gains?
You’d think that spending an hour a day sweating at the gym would be enough to guarantee good health. But a 2010 study in the American Journal of Epidemiology added to growing evidence that what you do during the rest of the day also makes a difference. The researchers followed 123,000 people for 13 years and found that men and women who spent more than six hours per day sitting down were 18 and 37 percent, respectively, more likely to die during the study than those who sat fewer than three hours per day. What’s most surprising is that these risks were completely unrelated to how much exercise the subjects reported getting.
Scientists aren’t yet sure why spending long periods of time sitting down should cause health problems, but they view it as a sign that the low-intensity activity associated with simply walking around and doing everyday chores makes an important contribution to health. Research at the University of Massachusetts Amherst suggests that it can also make a key contribution to weight loss, since it’s low-key enough that it doesn’t spark hunger to compensate for the calories burned. A forthcoming Amherst study compared a group of volunteers who sat all day (they even used wheelchairs to visit the bathroom) with a group that didn’t sit down at all. Preliminary results show that the difference in energy expenditure was hundreds of calories—but the level of appetite hormones and reported hunger in the two groups remained identical.
Of course, for people who work in office settings, walking around all day isn’t really an option. Some experts recommend scheduling regular “micro-breaks” every 30 to 60 minutes, in which you stand up, stretch, and walk