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Keywords:

  • exercise;
  • running;
  • BMI;
  • regional adiposity;
  • waist circumference

Abstract

  1. Top of page
  2. Abstract
  3. Introduction
  4. Research Methods and Procedures
  5. Results
  6. Discussion
  7. Acknowledgments
  8. References

Objective: Prior randomized and non-randomized training studies have failed to establish a dose-response relationship between vigorous exercise and weight loss; this failure may be due, in part, to their short durations and small sample sizes. The objectives of this study were to determine whether exercise reduces body weight and to examine the dose-response relationships between changes in exercise and changes in total and regional adiposity.

Research Methods and Procedures: This was a large prospective study of 3973 men and 1444 women who quit running (detraining), 270 men and 146 women who started running (training), and 420 men and 153 women who remained sedentary during 7.4 years of follow-up. The outcomes measured were weekly running distance, body weight, BMI, body circumferences, and bra cup size.

Results: There were significant inverse relationships between the changes in the amount of vigorous exercise (km/wk run) and the changes in weight and BMI in men (slope ± standard error: −0.039 ± 0.005 kg/km per week and −0.012 ± 0.002 kg/m2 per km/wk, respectively) and in older women (−0.060 ± 0.018 kg/km per week and −0.022 ± 0.007 kg/m2 per km/wk) who quit running, and in initially sedentary men (−0.098 ± 0.017 kg/km per week and −0.032 ± 0.005 kg/m2 per km/wk) and women (−0.062 ± 0.023 kg/km per week and −0.021 ± 0.008 kg/m2 per km/wk) who started running. Changes in waist circumference, an indicator of intra-abdominal fat, were also inversely related to changes in running distance in men who quit (−0.026 ± 0.005 cm/km per week) or started running (−0.078 ± 0.017 cm/km per week).

Discussion: The initiation of vigorous exercise and its cessation decrease and increase, respectively, body weight and intra-abdominal fat, and these changes are proportional to the change in exercise dose.


Introduction

  1. Top of page
  2. Abstract
  3. Introduction
  4. Research Methods and Procedures
  5. Results
  6. Discussion
  7. Acknowledgments
  8. References

Obesity is a pervasive condition. Sixty-five percent of U.S. adults were overweight in 2000, and 32% were obese (1). Furthermore, the percentage of men and women with a BMI of ≥30 kg/m2, the criterion for obesity, is substantially greater than it was from 1976 to 1980, when it affected 14.5% of the U.S. adult population (1). Obesity and increased body weight have important emotional, social, and medical consequences (2, 3), and this trend has prompted a search for hygienic and other strategies to prevent and reverse weight gain. Exercise is one preventive and therapeutic strategy that is attractive not only because of its effect on body weight, but also because of beneficial effects on other cardiovascular risk factors including insulin resistance, lipoproteins, and blood pressure (4, 5). Nevertheless, most weight control experts maintain that exercise is useful primarily in maintaining weight loss achieved by caloric restriction but is not effective alone (6, 7, 8, 9, 10, 11).

Several systematic reviews have failed to establish a dose-response relationship between exercise training and weight loss (8, 9). In contrast, cross-sectional data have repeatedly demonstrated significant dose-response relationships between higher levels of physical activityand lower body weight and body fat (12). For example, we observed in more than 100,000 runners that weekly running distance was inversely related to BMI (an index of total adiposity), body circumferences (indicators of regional adiposity), and bra cup size (13, 14). Although these cross-sectional analyses precisely described the dose-response relationships between body fat indices and running distances in men and women who have exercised for years, they were unable to distinguish whether the leanness of exercisers was due to weight losses or to the choices of lean men and women to run longer distances, i.e., self-selection bias (15).

This report uses data from the National Runners’ Health Study (13, 14, 16, 17), a study that recruited a large prospective cohort between 1991 and 1995 to examine further the utility of exercise as a weight loss strategy and the dose-response relationship between distance run and change in body composition. Evidence for a dose-response relationship was obtained by comparing changes in weight in men and women who started or quit running to changes in those who remained sedentary at both baseline and follow-up. The results provide strong evidence that changes in vigorous physical activity cause changes in weight that are proportional to the exercise dose.

Research Methods and Procedures

  1. Top of page
  2. Abstract
  3. Introduction
  4. Research Methods and Procedures
  5. Results
  6. Discussion
  7. Acknowledgments
  8. References

The current analyses are restricted to sedentary individuals who, of their own volition, began exercising vigorously, and vigorously active individuals who stopped running due to choice or injury. Men and women who completed the questionnaires but identified themselves on both surveys as being non-runners were also included.

The design and survey instruments for the National Runners’ Health Study have been described elsewhere (13, 14, 16, 17). The runners were solicited through a national running magazine (Runners’ World, Emmaus, PA) and at running events. Of those who were given the survey questionnaire, approximately 15% to 19% responded, the range representing our uncertainty of the actual number of questionnaires distributed. Our goal was to obtain a sufficiently large cohort for a prospective epidemiological study of health in vigorously active men and women rather than a comprehensive survey of runners; thus, recruitment ceased once a sufficient sample size was recruited.

The two-page questionnaire solicited information on demographics, running history, weight history, diet, current and past cigarette use, history of heart attacks and cancer, and medications for blood pressure, thyroid, cholesterol and diabetes at baseline and 7.4 years later. Running distance was reported in miles per week, body circumference in inches, and body weight in pounds. These measurements were then converted into kilometers, centimeters, and kilograms. No data were collected on energy intake. Runners were excluded if, on either survey, they reported that they smoked, followed strict vegetarian diets, or used thyroid medications, because of the possible influence of these factors on adiposity. Follow-up questionnaires were obtained from 78% of the participants. The study protocol was approved by the University of California Berkeley Committee for the Protection of Human Subjects, and all subjects provided written informed consent.

Change in BMI was calculated as the change in weight in kilograms between the baseline and follow-up questionnaires divided by the square of the average heights of the subjects in meters, from the two questionnaires. Self-reported waist and hip circumferences were elicited by the statement, “Please provide, to the best of your ability, your body circumference in inches” without further instruction. Bra cup sizes were coded on a five-point scale as 1 (A cup), 2 (B cup), 3 (C cup), 4 (D cup), and 5 (E cup or larger). Self-reported heights and weights from the questionnaires have been found previously to correlate strongly with their clinic measurements (unpublished correlations in 110 men were r = 0.96 for both). Self-reported waist, hip, and chest circumferences are somewhat less precise, as indicated by their correlations with their clinic measurements (r = 0.68, r = 0.63, and r = 0.77, respectively). The test-retest correlation for miles run per week on repeat questionnaires was r = 0.89.

Evidence for a dose-response relationship was obtained by comparing weight changes in men and women who initiated (training subset) or ceased (detraining subset) running to those of others who remained sedentary at both baseline and follow-up. The dose-response relationship between weight loss and increased exercise in those who started running was corroborated by a dose-response relationship between weight gain and decreased exercise in those who quit running.

Results are presented as means ± standard error (SE)1 or slopes ± SE, except where noted. Cut-off points for running distance categories were made to ensure reasonable sample sizes within categories and were defined before analyses. Categorization of men and women by running distance does not account for energy expenditure by other vigorous activities, but running was the primary exercise modality for these subjects.

Standard multiple regression analyses were used to adjust the changes in adiposity for the duration of follow-up and for age. Specifically, we used the regression model:

  • image

where α, β, υ, and δ are the regression coefficients fitted to the model and δ is the estimated training or detraining effect associated with each 1-km change in running distance. Men and women who were inactive at both baseline and follow-up were included in the regression analyses of both the training and detraining subsets.

Results

  1. Top of page
  2. Abstract
  3. Introduction
  4. Research Methods and Procedures
  5. Results
  6. Discussion
  7. Acknowledgments
  8. References

Subject Groups

Table 1 shows that there were 3973 men and 1444 women who ran at baseline but quit running before follow-up (detraining subset) and 270 men and 146 women who were non-runners at baseline and started running before follow-up (training subset). An additional 420 men and 153 women who reported not running at both baseline and follow-up serve as primary comparison groups in many of the analyses that follow. In the detraining subset, the decrease in running distance was associated with younger age and longer follow-up times. The decrease in running distance was significantly (p < 0.0001) associated with all baseline adiposity indices of both men and women. In the training subset, men who ran longer distances at follow-up had narrower waists at baseline but were indistinguishable from other men in this subset by age, follow-up duration, or other baseline indices of adiposity. Women in the training subset who ran farther at follow-up were younger and leaner at baseline.

Table 1.  Baseline characteristics (mean ± standard deviation) of the training subset (non-runners at baseline) and detraining subset (non-runners at follow-up).
      Circumferences (cm)  
  • NS, not significant.

  • *

    Negative values represent the decrease in running distance by quitting. Positive values represent the increase in running distance when starting from 0 km/wk.

Change in running distance (km/wk)*NAge (years)Follow-up (years)Body weight (kg)BMI (kg/m2)WaistHipChestBra cup (sizes)
Detraining subset         
 Male         
  None42045.9 ± 11.47.9 ± 1.381.8 ± 12.425.7 ± 3.588.8 ± 8.697.9 ± 8.8104.3 ± 7.9 
  −1 to −1571745.4 ± 10.88.0 ± 1.682.2 ± 11.925.8 ± 3.589.0 ± 8.097.9 ± 8.1105.5 ± 8.3 
  −16 to −31144546.7 ± 10.58.3 ± 1.780.0 ± 10.325.0 ± 2.887.3 ± 6.596.5 ± 7.6104.0 ± 7.3 
  −32 to −47107745.9 ± 10.88.6 ± 1.778.0 ± 9.724.4 ± 2.785.8 ± 6.395.2 ± 7.4102.9 ± 7.5 
  ≤−4873443.2 ± 11.68.7 ± 1.775.1 ± 9.423.6 ± 2.683.6 ± 6.093.9 ± 7.8101.6 ± 7.5 
  P (trend) <0.0001<0.0001<0.0001<0.0001<0.0001<0.0001<0.0001 
 Females         
  None15339.4 ± 8.57.7 ± 1.465.9 ± 12.924.0 ± 4.476.0 ± 10.898.3 ± 10.193.2 ± 8.12.4 ± 1.1
  −1 to −1958138.8 ± 9.87.9 ± 1.861.5 ± 8.822.6 ± 3.171.9 ± 7.994.8 ± 7.389.9 ± 6.02.1 ± 0.9
  −20 to −3953439.6 ± 10.08.1 ± 1.959.1 ± 8.221.8 ± 2.670.0 ± 7.093.0 ± 6.288.7 ± 5.32.0 ± 0.9
  ≤−4032936.0 ± 10.28.5 ± 1.858.0 ± 7.821.3 ± 2.568.9 ± 7.090.7 ± 6.387.9 ± 5.51.8 ± 0.8
  P (trend) <0.0001<0.0001<0.0001<0.0001<0.0001<0.0001<0.0001<0.0001
Training subset         
 Male         
  None42045.9 ± 11.47.9 ± 1.381.8 ± 12.425.7 ± 3.588.8 ± 8.697.9 ± 8.8104.3 ± 7.9 
  1 to 2316043.6 ± 11.07.5 ± 1.380.2 ± 11.125.1 ± 3.288.0 ± 7.796.4 ± 8.2103.8 ± 7.9 
  ≥2411043.0 ± 10.67.7 ± 1.579.9 ± 12.125.0 ± 3.286.4 ± 7.094.8 ± 7.6104.0 ± 7.3 
  P (trend) NSNSNSNS0.02NSNS 
 Females         
  None15339.4 ± 8.57.7 ± 1.465.9 ± 12.924.0 ± 4.476.0 ± 10.898.3 ± 10.193.2 ± 8.12.4 ± 1.1
  1 to 239336.9 ± 9.67.8 ± 1.661.0 ± 11.322.1 ± 3.371.8 ± 10.094.2 ± 8.189.9 ± 7.52.1 ± 1.0
  ≥245336.9 ± 8.27.8 ± 1.557.0 ± 7.221.3 ± 2.468.7 ± 8.391.6 ± 7.288.4 ± 5.52.0 ± 0.8
  P (trend) 0.03NS<0.0001<0.00010.00020.00010.0010.26

Effects of Exercise Cessation

Results are presented separately for women <45 years old and women ≥45 years old because the results show distinct differences between these two female age groups. Men's results did not seem to differ by age and, therefore, are presented without separation into age groups.

At baseline, running distance was inversely and significantly (p < 0.0001) associated with all adiposity indices of both men and women (Table 1). After these men quit running, their weight, BMI, and waist and chest circumferences significantly increased in proportion to the change in running distance (Table 2). These regression analyses are adjusted for mean age during the follow-up and for follow-up duration. Similarly, the body weights, BMIs, chest circumferences, and bra cup sizes of women ages ≥45 years who quit running increased also in proportion to the changes in running distance. Interestingly, among the women, the increases in body weight, BMI, chest circumference, and bra cup size were more than 2 SE larger in the older (≥45 years) than in the younger women, a difference suggesting that the severity of the deleterious effect of exercise cessation on these body aspects is affected by age. In addition to these exercise effects, the regression models show a general tendency for men and women to gain weight over time (i.e., positive coefficients for follow-up duration) that diminished with age (i.e., the negative coefficient for age).

Table 2.  Regression analyses of the changes in adiposity measures in the detraining subset during 7.4 years of follow-up (4393 men, 1597 women).
  Regression coefficient ± standard error 
  • Significance levels from multiple regression analyses are coded as:

  • *

    p < 0.05;

  • p < 0.01;

  • §

    p < 0.001; and

  • p < 0.0001.

 InterceptAge (years)Follow-up duration (years)ΔRunning distance (km/wk)
ΔBody weight (kg)    
 Males7.435 ± 0.785−0.171 ± 0.0100.652 ± 0.066−0.039 ± 0.005
 Females <45years−3.014 ± 2.0620.097 ± 0.045*0.658 ± 0.1510.008 ± 0.014
 Females ≥45years12.088 ± 3.041−0.224 ± 0.0500.243 ± 0.173−0.060 ± 0.018§
ΔBMI (kg/m2)    
 Males2.257 ± 0.246−0.052 ± 0.0030.205 ± 0.021−0.012 ± 0.002
 Females <45years−1.276 ± 0.7470.037 ± 0.016*0.251 ± 0.0550.002 ± 0.005
 Females ≥45years4.631 ± 1.095−0.085 ± 0.0180.083 ± 0.062−0.022 ± 0.007§
ΔWaist (cm)    
 Males3.834 ± 0.750−0.073 ± 0.010.431 ± 0.063−0.026 ± 0.005
 Females <45years−0.510 ± 2.4420.012 ± 0.0540.616 ± 0.175§−0.011 ± 0.017
 Females ≥45years6.765 ± 3.718−0.133 ± 0.061*0.556 ± 0.208−0.009 ± 0.022
ΔHip (cm)    
 Males3.312 ± 1.561*−0.075 ± 0.0190.363 ± 0.136−0.011 ± 0.011
 Females <45years−3.648 ± 2.4100.032 ± 0.0530.807 ± 0.1710.005 ± 0.016
 Females ≥45years6.393 ± 3.392−0.096 ± 0.0560.127 ± 0.187−0.028 ± 0.019
ΔChest (cm)    
 Males3.045 ± 0.931−0.096 ± 0.0120.505 ± 0.078−0.024 ± 0.006
 Females <45years−3.005 ± 1.7440.057 ± 0.0380.534 ± 0.126−0.007 ± 0.012
 Females ≥45years3.618 ± 2.649−0.110 ± 0.0440.455 ± 0.147−0.043 ± 0.016
ΔBra-cup (size)    
 Females <45years−0.149 ± 0.2270.005 ± 0.0050.038 ± 0.017*0.000 ± 0.002
 Females ≥45years0.086 ± 0.330−0.007 ± 0.0050.057 ± 0.019−0.006 ± 0.002

Figure 1 presents histograms of the mean increases in men's body weights, BMIs, and waist circumferences by their decreases in running distance. Mean increases in body weight and BMI of men who reduced their running distances by 1 to 15 km/wk or more were significantly larger than those of men who were non-runners at both baseline and follow-up. Each 16-km/wk reduction in running distance was associated with significant increases in body weight and BMI (there was a single exception, that of the difference between 1 to 15 and 16 to 31 km/wk). Men who had reduced their weekly distances by 32 km/wk or more by quitting had significantly greater increases in waist circumference than those who had smaller reductions in distance. The histograms that comprise Figure 2 show that the mean increases in the body weight, BMI, and bra cup size of older women who had reduced their running distance by 40 km/wk or more before quitting were significantly greater than those of older women who had made smaller reductions in running.

image

Figure 1. Detraining (running cessation). Mean changes in body weight, BMI, and waist circumference by decrease in running distance in 4393 men who reported that they quit running (N = 3793) or had remained sedentary (Decrease = None, N = 420). Significance levels above the bars correspond to comparisons with other categories by two-sample t test (e.g., p = 0.008 is the probability that runners who reduced their distance by 1 to 15 km/wk when they quit had the same mean increase in body weight as men who were sedentary at both baseline and follow-up, i.e., 0-km/wk change).

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image

Figure 2. Detraining (running cessation). Mean changes in body weight, BMI, and bra cup size by decrease in running distance in women who reported that they quit running (N = 1444) or had remained sedentary (Decrease = None, N = 153) by age groups. Significance levels above the bars correspond to comparisons with women ≥45 years of age who ran more than 40 km/wk at baseline by two-sample t test (e.g., p = 0.05 is the probability that women who remained sedentary had the same mean increase in body weight as women who decreased their distance by more than 40 km/wk). Other comparisons did not achieve statistical significance.

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Training Effects or Exercise Adoption

Table 3 presents the regression analyses for men and women who began running only after baseline. Older and younger women were analyzed together because of the small sample sizes and the absence of an indication that older women lost more weight.

Table 3.  Regression analyses of the changes in adiposity measures in the training subset during 7.4 years of follow-up (690 men, 299 women).
 Regression coefficient ± standard error
  • Significance levels from multiple regression analyses are coded as:

  • *

    p < 0.05;

  • p < 0.01;

  • §

    p < 0.001; and

  • p < 0.0001.

 InterceptAge (years)Follow-up duration (years)ΔRunning distance (km/wk)
ΔBody weight (kg)    
 Males5.88 ± 1.948−0.136 ± 0.0230.571 ± 0.186−0.098 ± 0.017
 Females5.376 ± 2.959−0.075 ± 0.0450.228 ± 0.269−0.062 ± 0.023
ΔBMI (kg/m2)    
 Males1.738 ± 0.615−0.042 ± 0.0070.194 ± 0.059§−0.032 ± 0.005
 Females1.246 ± 1.015−0.022 ± 0.0150.143 ± 0.092−0.021 ± 0.008
ΔWaist (cm)    
 Males4.778 ± 1.922*−0.077 ± 0.023§0.3 ± 0.183−0.078 ± 0.017
 Females2.941 ± 3.715−0.029 ± 0.0570.121 ± 0.3460.019 ± 0.031
ΔHip (cm)    
 Males0.235 ± 3.416−0.034 ± 0.0390.426 ± 0.344−0.011 ± 0.03
 Females7.61 ± 4.141−0.061 ± 0.065−0.408 ± 0.385−0.028 ± 0.034
ΔChest (cm)    
 Males5.294 ± 2.394*−0.083 ± 0.0280.152 ± 0.236−0.039 ± 0.02*
 Females1.418 ± 2.735−0.004 ± 0.041−0.011 ± 0.252−0.023 ± 0.022
ΔBra-cup (size)    
 Females0.462 ± 0.405−0.003 ± 0.006−0.016 ± 0.038−0.004 ± 0.003

In both men and women, the amounts of weight loss were proportional to the increases in running distance when adjusted for age and follow-up duration. Men's waist and chest circumferences also decreased significantly in relation to their increases in running distance. Figures 3 and 4 show that men and women who increased their running distances by 24 km/wk or more gained significantly less weight than those who remained sedentary. Increases in body weight and BMI were also significantly smaller in runners who started running 1 to 23 km/wk when compared with those who remained sedentary (albeit p = 0.06 for ΔBMI in men). Mean increases in waist circumferences were significantly lower in the men who started running than in those remaining sedentary. Sedentary women who began running appeared to decrease their bra cup sizes in proportion to their running distances (Figure 4), but this phenomenon did not attain statistical significance.

image

Figure 3. Training (running initiation). Mean changes in body weight, BMI, and waist circumference by increase in running distance in initially sedentary men who remained sedentary (Increase = None, N = 420) or began running (N = 270). Significance levels above the bars correspond to comparisons with the mean change for men who remained sedentary (*) or increased their distance relative to those running 1–23 km/wk (†).

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image

Figure 4. Training (running initiation) Mean changes in body weight, BMI, and bra cup size by increase in running distance in initially sedentary women who remained sedentary (Increase = None, N = 153) or began running (N = 146). Significance levels above the bars correspond to comparisons with the mean change for women who remained sedentary. N.S., not significant.

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Discussion

  1. Top of page
  2. Abstract
  3. Introduction
  4. Research Methods and Procedures
  5. Results
  6. Discussion
  7. Acknowledgments
  8. References

These results for runners who became sedentary and non-runners who became runners provide consistent evidence that exercise, in the mode of distance running, reduces body weight and adiposity. These results are important and supplement those obtained from interventional trials, because our large sample size permits a level of statistical power unattainable in most controlled clinical trials. Also, the fact that both exercise cessation and adoption increased and decreased body weight, respectively, strengthens the argument for exercise being causally related to the change.

These results are consistent with our prior randomized controlled clinical trials demonstrating that sedentary men assigned to a 1-year running program lost significantly more weight and body fat than men who remained sedentary (18, 19) and that running plus caloric restriction produced more weight loss than caloric restriction alone (20). In those and the present results, the changes in running distance correlate directly with the changes in body weight. Other randomized controlled trials have also demonstrated significant weight loss in men using a variety of exercise training interventions, including 16 weeks of training on cycle ergometers at 70% of maximum heart rate in older men (21), and 12 weeks of walking or light jogging requiring an energy expenditure of 3500 kcal/wk (22) or 4900 kcal/wk (23). In contrast, some studies, including one requiring 90 minutes of vigorous exercise per week, observed no weight reduction (24). These randomized and other non-randomized exercise training studies have been summarized elsewhere (9). Their collective interpretation suggests that exercise produces significant weight loss; however, these reports include in total only about 1000 exercise-trained subjects, a number far smaller than the sample size of the present report.

The current study also differs from previous studies by the long follow-up duration of 7.4 years, or 385 weeks. Most exercise training studies are of <16 weeks’ duration, and few extend beyond a year (9). Weight loss initially achieved by either diet or exercise is often not maintained over long-term follow-up (10). The cause of this weight regain is unclear but may relate to the reversal of behavioral change (11). Weight loss in short-term exercise training studies is directly related to energy expenditure and is ∼85% of expected, based on the estimated exercise energy deficit (9). Weight loss in studies lasting 20 to 60 weeks achieves only ∼30% of the project loss and may not have a dose-response relationship to energy expenditure (9). Nevertheless, given the large sample size in the present study, it is likely that exercise does indeed produce weight loss, in contrast to previous conclusions.

Waist circumferences decreased in men who started running and increased in men who quit, and these changes were also highly significantly related to the changes in running distance. Waist circumference reflects abdominal obesity and is an easily obtainable estimate of intra-abdominal fat (25). Intra-abdominal fat is associated with multiple coronary artery disease risk factors, including hypertension, insulin resistance, diabetes, and lipoprotein disorders, as well as coronary artery disease itself, and these relationships are independent of total body fat (26). A recent review (9) found that some (23, 27, 28, 29), but not all (30, 31), studies suggest that exercise training reduces intra-abdominal fat. Neither this review nor clinical guidelines from the NIH (8) could establish a dose-response relationship between physical activity and abdominal obesity. In contrast, the present results, using a large sample size, document a strong relationship between increasing exercise and reducing abdominal obesity and support a clear dose relationship.

In women, body weights increased with running cessation and decreased with the start of exercise training in a dose-dependent manner. Others (32, 33, 34, 35) have also demonstrated weight loss from exercise in various randomized controlled clinical trials of women. We also found that chest and bra cup sizes increased in older women who stopped running in proportion to the decreases in running distance. These observations were not confirmed by decreases in chest circumference and bra cup size in women initiating a running program, possibly because of a small sample size and less statistical power. Our recent article on the cross-sectional relationships between indices of adiposity and running distance in 41,582 female runners (13) showed that waist, hip, and chest circumferences declined significantly with running distance across all age groups, but the declines were 52% to 58% greater in older than in younger women. Thus, there may be a generally stronger effect of exercise on body weight in older women that would make their exercise-related changes in adiposity more easily detected than in younger women.

Currently, exercise is usually prescribed as an adjunct to dieting in inducing and maintaining weight loss (6, 7, 8, 9). Persons who successfully maintain substantial weight loss usually engage in physical activity in addition to following low-fat diets and monitoring food portions and body weight (36). A meta-analysis suggests that adding exercise to dieting improves long-term maintenance of weight loss (7), and at least one study suggests that this might occur in a dose-dependent manner (37), although others suggest that the benefit is modest and might not provide any additional benefit beyond increasing the total caloric deficit (11). The present results suggest that vigorous exercise, such as running, can reduce body weight and body fat, independently of dietary change.

The main limitation of the present study is that running distance and anthropometric values were based on self-report. We have validated our methods against clinical measurements and repeat questionnaires. Furthermore, vigorous-intensity activity is generally reported more accurately than light and moderate activities such as walking (38). Running is an attractive exercise to study by self-report because exercise-energy expenditure can be estimated from distance run alone (39) and, therefore, may be more accurately assessed than activities that require both duration and intensity for their calculations. Measurement error is likely to result in the regression analyses underestimating the training and detraining effects. Specifically, measurement errors associated with the dependent variables (Δadiposity) are included as part of the total residual error and do not affect the estimated coefficients except to inflate their SEs, and errors in measuring the independent variable (Δdistance) will cause the estimated coefficient to be biased toward zero (40). Despite the possible limitations of self-report, the present study is based on sample sizes unachievable in most clinical trials.

In conclusion, the present results using both exercise cessation and initiation suggest that exercise has direct effects on body weight and intra-abdominal fat. Such observations suggest that vigorous exercise may be underestimated for its ability to reduce body fatness independently of dietary interventions.

Acknowledgments

  1. Top of page
  2. Abstract
  3. Introduction
  4. Research Methods and Procedures
  5. Results
  6. Discussion
  7. Acknowledgments
  8. References

We gratefully acknowledge the assistance of Kathryn Hoffman for her assistance in organizing and overseeing the follow-up of these runners and Thomas Livingston for his editorial comments. This research was supported, in part, by Grants HL-45652 and HL-72110 from the National Heart, Lung, and Blood Institute and Grant DK066738 from the National Institute of Diabetes and Digestive and Kidney Diseases of the NIH.

Footnotes
  • 1

    Nonstandard abbreviation: SE, standard error.

  • The costs of publication of this article were defrayed, in part, by the payment of page charges. This article must, therefore, be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

References

  1. Top of page
  2. Abstract
  3. Introduction
  4. Research Methods and Procedures
  5. Results
  6. Discussion
  7. Acknowledgments
  8. References
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