The first virtuous circle I ever remember finding was the positive relationship between Byetta and exercise. "The more weight I lost and the more I exercised, the more energy I had," I wrote in my forthcoming book, Losing Weight with Your Diabetes Medication. "All this feedback gave me more motivation than ever to keep on losing weight."
Now we have proof of my anecdotal experience. A research report that the Journal of Sport & Exercise Psychology just published last month looked at the question, "Exercise makes you feel good, but does feeling good make you exercise?" Robert Carels, associate professor of psychology at Bowling Green State University in Bowling Green, Ohio, and three colleagues concluded it did.
Dr. Carels kindly sent me an electronic copy of the full text of the article. They studied a group of 36 obese dieters in a 16-week behavioral weight-loss program, evaluating their daily mood mornings and evenings as well as before and after they exercised. They also recorded what type of exercise they did and its intensity and duration.
While exercise alone doesn't burn a whole lot of calories, we've known all along that it is an important factor in successfully losing weight and keeping it off. Earlier studies that Dr. Carels and his colleagues cite showed that when our mood is negative, we have a harder time to get going with our exercise and to keep it up.
"When individuals experience a negative mood, they may feel less confident in their ability to perform an action," the new article says. They have "diminished efficacy expectations."
I know. As recently as yesterday, when I was a bit down, I had to force myself to exercise. And even then I didn't work out with my usual intensity.
Other earlier studies that the current article cites concluded that exercise of moderate rather than low intensity and greater than 20 minutes typically reported greater enhancement of the exerciser's mood. Up to a point.
Two earlier studies -- one in 1992 and the other is 2005 -- found that those people who worked out at high or maximum intensity -- like greater than 80 percent of their maximum heart rate -- experienced "inconsistent and sometimes even undesirable changes in mood." But Dr. Carels and his colleagues hardly pushed their exercising dieters that far.
In the new study they encouraged the volunteers to progress toward walking -- a low to moderate-intensity exercise -- for 30 minutes to an hour every day. Is that enough? They don't know yet what the optimal duration for maximum mood enhancement is.
But in the current study the longer and harder that the volunteers worked out the better was their mood for at least 2 to 4 hours and often for the rest of the day. On the days that they worked out their mood was better than when they stayed sedentary.
It wasn't easy to get these people off their couches. It seldom is. But, "as participants became more comfortable with exercise and/or more confident in their ability," the study says, "they may have experienced fewer concerns before initiating exercise."