Maintaining Vigorous Activity Attenuates 7-yr Weight Gain in 8340 Runners

Paul T. Williams

Disclosures

Med Sci Sports Exerc. 2007;39(5):801-809. 

In This Article

Results

There were 6119 men and 2221 women who reported running within ± 5 km·wk-1 of their baseline running distance (19% of the surviving cohort). Men and women, respectively, on the baseline surveys were, on average, middle aged (mean ± SD: 45.3 ± 10.1 and 39.6 ± 9.7 yr), college educated (16.7 ± 2.4 and 16.0 ± 2.3 yr of education), relatively lean (BMI of 24.1 ± 2.7 and 21.5 ± 2.7 kg·m-2), narrow waisted (85.1 ± 6.3 and 69.3 ± 7.3 cm), and had run for 13.8 ± 8.0 and 10.4 ± 5.9 yr. Women's baseline hip circumference averaged 91.9 ± 7.0 cm. The men gained 0.33 ± 0.64 kg and added 0.30 ± 0.71 cm around their waists annually during 7.5 ± 3.2 yr of follow-up. Women annually gained an average of 0.31 ± 0.69 kg in weight, 0.36 ± 1.07 cm in waist circumference, and 0.26 ± 1.08 cm in hip circumference during their 7.2 ± 2.3 yr of follow-up. The length of follow-up varies across individuals because of differences in when they were recruited and when their follow-up questionnaires were returned.

Annual Increases in Weight by Age, Stratified by Running Distance

Average body weight, BMI, waist circumference, and hip circumference (women only) increased significantly over time for all age classes, regardless of distance run ( Table 1 , column 1). Young adults (18- to 24-yr-old men and 18- to 30-yr-old women) experienced the greatest annual increases in body weight, BMI, waist circumference, and hip circumference. In men, the rate of increase was diminished by over half after age 25 and by two thirds after age 45, relative to the increases in young men. In women, annual increases in waist and hip circumference rates diminished by over half after age 29.

Individuals running modest (0-23 km·wk-1), intermediate (24-47 km·wk-1), or prolonged distances (≥ 48 km·wk-1) also demonstrated statistically significant annual increases in body weight, BMI, and waist circumference through age 64 in men and in all age groups in women ( Table 1 , columns 2-4). However, between ages 25 and 54 in men and 30 and 49 in women, the average annual gain in weight and BMI attenuated for those who ran intermediate and longer running distances. Those running ≥ 48 km·wk-1 experienced only half the average annual increase in total weight and BMI as those who maintained < 24 km·wk-1. Waist circumference in men 25 yr and older also tended to increase significantly less for those who maintained their running distance ≥ 48 km·wk-1 vs < 24 km·wk-1.

Annual Increases in Weight by Running Distance, Stratified by Age

Table 2 presents the regression slopes for annual changes in body weight, BMI, and waist circumference versus maintained running distance (km·wk-1) within each age group. Annual increases in adiposity decreased significantly with running distance in young to middle-aged men (25-54 yr) but not in older men. Running produced progressively less attenuation of annual weight gain as the men got older. This was confirmed by the statistically significant interaction between the effects of age and running distance on annual changes in weight and BMI. In contrast, annual increases in waist circumference decreased with running distance in men 25 and older, regardless of age, and there was no significant interaction between age and distance. This suggests that the attenuation of the annual gains in waist circumference can be estimated by the single slope for pooled data adjusted for age (-0.004 ± 0.001 cm·yr-1 per km·wk-1, P < 0.0001) rather than by separate coefficients for each age group.

In women under 50, maintaining longer running distances significantly reduced annual increases in total weight and BMI ( Table 2 ). The attenuation of age-related weight gain was not significant in older women, but this may be partly attributable to limited statistical power, because there was no significant interaction between age and running distance. The pooled data adjusted for age suggest that each kilometer run per week attenuated the annual increase in body weight by -0.006 ± 0.001 kg, in BMI by -0.002 ± 0.000 kg·m-2, and in waist circumference by -0.003 ± 0.001 cm. Maintaining longer running distances also attenuated annual increases in hip circumference (not displayed) in women 30-39 yr old (-0.006 ± 0.002 cm·yr-1 per km·wk-1, P = 0.02) and 40-49 yr old (-0.007 ± 0.002 cm·yr-1 per km·wk-1, P = 0.002) but not in younger (-0.004 ± 0.006 cm·yr-1 per km·wk-1, P = 0.50) or older women (-0.005 ± 0.003 cm·yr-1 per km·wk-1, P = 0.07). However, there was, again, no significant interaction between age and distance, and the pooled slope for the annual attenuation in hip circumference per kilometer run per week, adjusted for age, was -0.006 ± 0.001 cm·yr-1 per km·wk-1, P < 0.0001.

Percentiles of Annual Weight Change by Running Distance

Figures 2 and 3 present the differences in the annual changes in body mass, BMI, and waist circumference between those who ran less than 24 km·wk-1 versus 24-47 km·wk-1 (left panels) and those who ran less than 24 km·wk-1 versus ≥ 48 km·wk-1 (right panels). Negative heights mean smaller annual increases in high- versus low-mileage runners. The differences are presented separately by age (x-axis) and by percentile of weight or circumference change (see legend). For example, the difference in the 90th percentile of BMI change is the 90th percentile of BMI among runners who ran ≥ 48 km·wk-1 minus the 90th percentile of BMI among runners who ran < 24 km·wk-1. The bars for the 10th, 25th, 50th, 75th, and 90th percentiles would all have the same heights if running produced the same expected reduction in annual weight gain across all percentiles (i.e., if running more miles shifted the entire distribution of BMI by a fixed amount). In contrast, the middle-right panel of Figure 2 shows that in 25- to 34-yr-old men, the 50th, 75th, and 90th percentiles of BMI change were significantly less for those who maintained ≥ 48 km·wk-1 than for those who maintained running distances of less than 24 km·wk-1, whereas the 10th and 25th percentiles of BMI change did not differ significantly between the higher- and lower-mileage runners. The length of the bars increase progressively from the 10th through the 90th percentiles, and this trend is statistically significant (P = 0.008), suggesting further that running does not diminish weight gain uniformly but, rather, that the degree of attenuation increases with the percentile of BMI.

Figure 2.

Difference in the annual change in body mass (top), BMI (middle), and waist circumference (bottom) between men who ran less than 24 km·wk-1, from those running 24-47 km·wk-1 (left), and from those running ≥ 48 km·wk-1 (right). Results are presented by age groups (x-axis) and percentile of weight change (legend). Significance levels for differences from zero are designated by symbols. Probabilities presented above the bars are for the significance of a linear trend going from the smallest to the highest percentile (percentile effect). SE are shown in brackets.

Figure 3.

Difference in the annual change in body mass (top), BMI (middle), and waist circumference (bottom) between women who ran less than 24km·wk-1, from those running 24-47 km·wk-1 (left), and from those running ≥ 48 km·wk-1 (right). Results are presented by age groups (x-axis) and percentile of weight change (legend). Significance levels for differences greater than zero are designated by symbols. Probabilities presented above the bars are for the significance of a linear trend going from the smallest to the highest percentile (percentile effect). SE are shown in brackets.

Figure 2 shows that men 35-54 yr old who consistently ran between 24 and 47 km·wk-1 were less likely to have larger annual increases in weight and BMI than men who ran < 24 km·wk-1. Moreover, the attenuation of weight gain depended on the amount of exercise, the percentile of weight gain, and the age of the men. Specifically, the attenuation of weight gain increased progressively from the lowest to highest weight and BMI percentile (percentile effect). These effects were more pronounced when men who maintained ≥ 48 km·wk-1 are compared with those who maintained < 24 km·wk-1 (Fig. 2, right panels) than when men who ran 24-47 km·wk-1 are compared with those who ran < 24 km·wk-1 (left panel, exercise dose effect). In men, there is a clear trend for age to reduce the attenuating effects of exercise on annual gains in the 50th, 75th, and 90th percentiles of weight and BMI. Figure 2 also shows that annual increases in waist circumference were attenuated by running and that the degree of attenuation was greatest at the 90th percentile of waist circumference, was intermediate at the 75th percentile, and was modest but significant at the 50th percentile of waist circumference. The degree of attenuation was similar across age groups after age 35.

The effects of exercise maintenance on the percentiles of weight and BMI in women are generally consistent with those observed in men (Fig. 3). Women 30-49 yr old who consistently ran between 24 and 47 km·wk-1 or ≥ 48 km·wk-1 had smaller annual increases in weight and BMI than those who ran < 24 km·wk-1. Also, the attenuation of weight gain increased progressively from the lowest to highest weight and BMI percentile. The difference between maintaining 24-47 km·wk-1 and maintaining ≥ 48 km·wk-1 was less evident for women than for men. Age-related increases in the 50th, 75th, and 90th percentiles of waist circumferences were also diminished in women 30-39 yr old by running at least 24 km·wk-1 and in women 40-49 yr old by running at least 48 km·wk-1.

In men, years of education were associated with significantly smaller increases in BMI and waist circumference (P = 0.001). In women, parity was associated with significantly greater increases in BMI (P = 0.02) but not waist or hip circumference, whereas education was unrelated to changes in BMI and body circumference. Adjustment for education and parity did not affect the differences reported.

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