To slim as you age, add weights

Trying to stay trim as you age? Surprisingly, if you're cutting calories to lose weight, adding weights to your weight loss regimen could be more effective than beginning a walking programme, according to a new study that adds to growing evidence that weight training is important for vigorous ageing.

Successful weight loss is never easy, as most of us know from experience, and becomes more difficult with age. Instead of losing or maintaining weight as we grow older, most of us gain a pound or two each year during middle age.

At the same time, we also often begin naturally to lose some of our muscle mass, so that our bodies wind up increasingly composed of fat. This change in body composition matters, because fat tissue is less metabolically active than muscle.

As the percentage of our body composed of fat tissue rises, our metabolic rates fall and we burn fewer calories throughout the day, predisposing us to continued weight gain. We also become less strong, of course, as our muscles shrink.

So most experts agree that
the ideal weight-loss program me for most people would maximise fat loss while sparing muscle mass. But this balance is difficult to achieve, since, typic-
ally, when we drop a pound while
dieting, as much as a third of that
loss can come from muscle, with the rest composed of fat.

Some past studies have hinted that exercising while cutting calories might help to lessen this muscle loss. But most of those studies have been small and involved relatively young people or only one gender.

For the new study, which was published in Obesity, researchers at Wake Forest University in Winston-Salem, North Carolina, and other institutions decided to focus on both men and women older than 60. They also set out to enroll African-American as well as the Caucasian participants most earlier studies used. In the end, they wound up with 249 participants who were overweight or obese and sedentary.

The researchers measured their body compositions and leg-muscle strength and assessed their diets. Then they randomly assigned the volunteers to one of three groups.

Some began a basic calorie-reduction plan, during which they cut their food intake by an
amount expected to help them
lose 7 to 10% of their body weight
over the coming months. For most of them, this meant a reduction of about 300 calories a day. The members of this group were asked not to exercise.

Another group also cut their calorie intake. But at the same time, they began a supervised aerobic exercise programme consisting of walking briskly on a track for 45 minutes four times per week.

The third group likewise reduced calories but also began a weight-training programme. Four times a week, they worked with trainers at a gym to complete a full-body resistance training routine using weight machines.

Dissimilar weight loss

All of the volunteers continued their particular programme for 18 months. By the end of that time, everyone had dropped weight. But there were notable differences in the amount and type of weight that had been lost in each group.

The men and women in the group that had cut calories but not worked out had lost an average of about 12 pounds each. Those who had cut calories and walked had dropped far more weight, about 20 pounds each, while those who had dieted and weight trained likewise had lost about 20 pounds per person.

But the weight loss among walkers and weight trainers was qualitatively different, their new body-composition scans showed. The weight trainers had lost about 2 pounds of muscle and 18 pounds of fat, while
the walkers had dropped about 4 pounds of muscle and 16 pou nds of fat. The group that had dieted and not exercised had lost about 2 pounds of muscle.

In effect, the walkers had lost more muscle mass in total and as a percentage of their weight loss than either of the other two groups, including those who had not exercised at all.

That finding surprised the researchers, said Kristen M Beavers, an assistant professor of health and exercise science at Wake Forest and the study's lead author. It would have worried them, too, she said. But subsequent tests of muscular strength showed that, relative to their new, lower body weights, the men and women who had exercised in any way had stronger legs than they had had 18 months before. Those who had remained sedentary did not have stronger legs.

Overall, the study's results imply that walking could have limitations as a weight-loss aid for older dieters, Beavers said. But they also suggest that for healthy weight loss, many of us might consider at least occasionally walking to the gym and, once there, picking up some weights.