Regular moderate to vigorous physical exercise in the 20 years leading up to middle age is linked to smaller gains in weight and waist size, particularly for women, according to US researchers who stressed the importance of doing at least 30 minutes of physical activity every day throughout young adulthood to help minimize middle age spread.
Dr Arlene L Hankinson, of the Feinberg School of Medicine, Northwestern University, Chicago, and colleagues looked at links between higher activity levels and changes in body mass index (BMI) and waist circumference over 20 years in young adults. They wrote about their findings in the December 15 issue of JAMA.
Obesity has been rising steeply in the US for the last 35 years, to the point where today, over 30 per cent of American adults are now obese, a condition that brings with it serious life-changing consequences such as chronic ill health and disability.
The researchers wrote that while many studies have looked into treatments for obesity, there is sparse evidence on how physical activity may prevent long-term weight gain, particularly during those years when the highest risk of putting on weight occurs.
For their investigation they used data from the Coronary Artery Risk Development in Young Adults (CARDIA) prospective longitudinal study, which includes 20 years of follow up covering the period 1985/86 to 2005/06. CARDIA has been funded by the National Heart, Lung, and Blood Institute of the National Institutes of Health since 1983.
3,554 men and women aged between 18 and 30 from Chicago; Birmingham in Alabama, Minneapolis; and Oakland in California enrolled on the study.
As well as collecting data on physical measurements such as weight, height and waist circumference, the researchers collected information about exercise and physical activity. From this they sorted the participants into three groups of high, moderate or low exercisers for men and women separately, according to their scored level of regular physical activity when they enrolled on the study.
During the follow up period the participants filled in surveys that asked them questions on levels of moderate and vigorous physical activity in the previous year; the questions covered 13 specific areas, including work-related, home-based, sport, and exercise activity.
Hankinson and colleagues then analyzed this physical activity data against annual average changes in BMI and waist circumference. BMI stands for Body Mass Index, a measure of obesity used in research, it is equal to a person’s weight in kilos divided by their weight in meters squared (kg/m2).
The results of the analysis showed that:
- For both sexes, and even more so for women than for men, keeping to high levels of activity over the 20 years preceding middle age was linked with smaller gains in BMI and waist circumference, compared with low activity. This was after adjusting for race, BMI at start of study, age, education, cigarette smoking, use of alcohol, and diet (energy intake).
- Men who kept up high levels of physical activity over the follow up gained on average 2.6 fewer kg (5.7 fewer lb) compared to the low activity group (0.15 vs 0.20 BMI units per year respectively).
- Women who kept up a high level of physical activity in the 20 years before reaching middle age gained on average 6.1 fewer kg (13.5 fewer lb) than women in the low activity group (0.17 vs 0.30 BMI units per year respectively).
- There was a similar pattern in waist size change: men who maintained high activity over the follow up gained on average 3.1 fewer cm (1.2 fewer ins) around the waist compared to the men in the lower activity group (0.52 vs 0.67 cm per year respectively).
- Women who maintained high activity gained 3.8 fewer cm (1.5 fewer cm), compared to the low activity group (0.49 vs 0.67 cm per year respectively).
- Weight gain in men and women who exercised moderately or inconsistently over the 20 years follow up was no different from that of men and women in the low activity groups.
The researchers concluded that:
“Maintaining high activity levels through young adulthood may lessen weight gain as young adults transition to middle age, particularly in women. “
They stressed that “the magnitude of weight change was more than twice as large among women compared with men”.
Plus, men and women who stuck to the government recommended 150 minutes of moderate exercise per week gained significantly less weight that those who did not.
“Our results reinforce the role of physical activity in minimizing weight gain and highlight the value of incorporating and maintaining at least 30 minutes of activity into daily life throughout young adulthood,” they added.
“Maintaining a High Physical Activity Level Over 20 Years and Weight Gain.”
Arlene L. Hankinson, Martha L. Daviglus, Claude Bouchard, Mercedes Carnethon, Cora E. Lewis, Pamela J. Schreiner, Kiang Liu, Stephen Sidney.
DOI:10.1001/jama.2010.1843
Additional source: JAMA and Archives Journals.
Written by: Catharine Paddock, PhD