People who keep up an active lifestyle into middle-age gain fewer pounds and inches over time -- and the benefit may be even greater for women than men, a new study finds.

The fact that consistently active people gain less weight over the years may not come as a surprise. But little in the way of research evidence actually supported that notion.

Most studies on physical activity and weight have focused on exercise as a way to shed excess pounds, rather than a way to ward off the padding that so commonly creeps up with age.

The new study, published Tuesday in the Journal of the American Medical Association, suggests that becoming active at a young age, and then keeping it up, can indeed thwart mid-life love handles.

Researchers found that among nearly 3,600 young U.S. adults followed for 20 years, men who were "habitually" highly active over that time put on about 6 fewer pounds, on average, than men who exercised consistently but at relatively low levels. They also saw their waistlines expand by about an inch less.

And among women, the most active gained 1.5 fewer inches around the middle and 13 fewer pounds.
"It's the maintenance of the physical activity that's the important thing," said lead researcher Dr. Arlene L. Hankinson, of Northwestern University in Chicago.

"It's not so much about achieving some dramatically high activity level," Hankinson said in an interview, "It's about maintaining a level of daily physical activity over time."

The team measured the subjects' typical exercise, housework and job activities using a scoring system that describes intensity and duration. It yields a total of "exercise units" that reflect a person's overall high, moderate or low activity level. It also allowed the researchers to gauge whether participants maintained a consistent activity level (regardless of specific activities) over the years.

In general, health experts recommend that adults try to get at least 30 minutes of moderate-intensity exercise -- like brisk walking -- on five days out of the week. In exercise unit terms, that would yield a moderate activity level. But whether it is enough to prevent excess weight gain over time has been unclear.

The current study included 3,554 men and women who were between the ages of 18 and 30 when the study began in the mid-1980s. At the outset and periodically over the next 20 years, they reported on their typical physical activity levels.

Of the men, 46 percent were consistently active during the study period, as were 42 percent of the women.

The researchers divided those habitual exercisers into three groups: lower, moderate and higher activity. In general, men and women who were most active -- and, it turned out, gained the least weight -- exercised for more than the widely recommended 30-minutes-a-day.

However, Hankinson's team also found benefits linked to more moderate levels of exercise.

They found that men who consistently got 30 minutes of exercise on five days out of the week gained about 4 fewer pounds than their less-active counterparts. Women with that activity level gained about 10 fewer pounds than women who got less exercise.

"Thirty minutes a day, five days a week is a really great target," Hankinson said.

And for people who feel they are too busy for a daily trip to the gym, she pointed out that there are many ways to fit exercise in.

"It should be about finding an activity that you actually like and can maintain. But you should also look at all the choices you make in your daily life," Hankinson said. "Do you walk to the store, take the stairs instead of the elevator, park your car farther away so you have to walk more?"

It's interesting, according to the researchers, that women seemed to reap a greater benefit from regular exercise. "This is the first study to show that the association between physical activity and weight is stronger in women than men," Hankinson said.

The reasons are unclear, and it could simply be related to how the study data were collected: Men may be more likely than women to overestimate their activity levels, for example.

Hankinson said further research should look into whether women and men really do get different weight benefits from long-term physical activity.

But even though exercise is a good weapon in the battle of the bulge, people probably should not expect to still have their 20-year-old physique at the age of 40.

In this study, even the most active men and women typically gained some weight and waistline inches over time. Some amount of middle-age spread, the researchers note, may be largely unavoidable