Now that the holidays are here, New Year's resolutions to lose weight won't be far behind. So just in time, researchers report that keeping up a regular exercise regimen may be your best bet when it comes to keeping extra pounds at bay.
It's not exactly ground-breaking advice, and perhaps not what most of us want to hear, but the new study led by Dr. Arlene Hankinson at Northwestern University confirms that consistent physical activity helps to prevent weight gain.
In her analysis, Hankinson measured body mass index and waist circumference among more than 3,400 men and women enrolled in a heart study. The trial was ideal for investigating the effects of exercise on weight since the subjects were followed over 20 years, from 1985-86 through 2005-06. Overall, men who were the most active gained 2.6 kg fewer per year than those who were least active, while the women with the highest level of physical activity enjoyed even greater benefit they gained 6.1 kg less per year than women in the lowest activity group. (More on Time.com: Fitness Tech: 10 Cool Ways to Get in Shape)
"It didn't matter if you were normal weight, overweight or obese in this study," says Hankinson of the results. "You don't have to have a BMI of less than 25 to get benefits from physical activity. So it's never too late."
Dr. Tim Church, director of preventive medicine at Pennington Biomedical Research Center, says "to me, it's crystal clear that weight is about diet and about physical exercise. The relative percentage of each is something we will debate until the end of time, but it's nave to throw either physical activity or diet out the window, and this study is strong evidence for keeping physical activity in the discussion."
Despite the intuitive connection between physical activity and weight loss, in recent years, there have been conflicting reports about whether exercise can actually help people shed pounds. Much of that confusion, says Hankinson, may derive from the fact that losing weight once you are overweight or obese is one thing, while preventing weight gain regardless of your size is another. She also notes that short-term studies of the effect of exercise on weight may be misleading, since it's difficult for people to maintain a regular, intensive program of physical activity. "I think the studies looking at activity for weight loss are consistent, and show that physical activity is effective," she says. "The problem is that most people either can't maintain that level of activity for long periods of time compared to changes in their diet, and so we see that physical activity is less effective in having an immediate impact on weight."
In her analysis, Hankinson stratified the subjects into low, moderate and high activity levels, based on the frequency and consistency with which the volunteers exercised. Not surprisingly, after 20 years, those who were able to maintain the highest level of activity showed the least weight gain. She notes that exercise does not prevent weight gain completely. "Weight gain overall is inevitable with age, and highly active people still did gain weight," she says. But they gain less weight than those who are only moderately or inconsistently active. (More on Time.com: Want to Eat Less? Imagine Eating More)
Hankinson says her findings should establish that regular and consistent exercise at a moderate intensity is effective in preventing weight gain, particularly over time, but that some people may find the results discouraging. In the study, those who exercised at a moderate level gained as much weight as those who were only minimally active. But that doesn't mean that only marathoners can stave off middle-age creep, says Church. He notes that the heart trial from which the data were gleaned involved a relatively intense physical activity program, so that when the volunteers were divided by whether or not they met the federal recommendation of at least 150 minutes of exercise a week, those who did gained less weight than those who did not. "There were clear differences in the amount of weight that wasn't gained in those who met the recommendations," he says.
Hankinson agrees. "The federal guidelines of 150 minutes of moderate activity a week is what everyone should go for at a minimum," she says. "It's about doing what works for you and, most importantly, keeping it up."