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Original Research |

Effects of Exercise Amount and Intensity on Abdominal Obesity and Glucose Tolerance in Obese Adults: A Randomized TrialEffects of Exercise on Obesity and Glucose Intolerance

Robert Ross, PhD; Robert Hudson, MD, PhD; Paula J. Stotz, MSc; and Miu Lam, PhD
[+] Article, Author, and Disclosure Information

† Deceased.


From Queen's University, Kingston, Ontario, Canada.

Grant Support: By the Canadian Institutes of Health Research (grant OHN-63277).

Disclosures: Authors have disclosed no conflicts of interest. Forms can be viewed at www.acponline.org/authors/icmje/ConflictOfInterestForms.do?msNum=M14-1189.

Reproducible Research Statement:Study protocol: Published elsewhere (8). Statistical code: Available from Dr. Ross (e-mail, rossr@queensu.ca). Data set: Not available.

Requests for Single Reprints: Robert Ross, PhD, School of Kinesiology and Health Studies, Queen's University, 28 Division Street, Kingston, Ontario K7L 3N6, Canada; e-mail, rossr@queensu.ca.

Current Author Addresses: Dr. Ross and Ms. Stotz: School of Kinesiology and Health Studies, Queen's University, 28 Division Street, Kingston, Ontario K7L 3N6, Canada.

Dr. Lam: Department of Public Health Sciences, Queen's University, 62 Fifth Field Company Lane, Kingston, Ontario K7L 3N6, Canada.

Author Contributions: Conception and design: R. Ross, R. Hudson, M. Lam.

Analysis and interpretation of the data: R. Ross, P.J. Stotz, M. Lam.

Drafting of the article: R. Ross, P.J. Stotz, M. Lam.

Critical revision of the article for important intellectual content: R. Ross, P.J. Stotz, M. Lam.

Final approval of the article: R. Ross, M. Lam.

Statistical expertise: M. Lam.

Obtaining of funding: R. Ross, R. Hudson, M. Lam.

Administrative, technical, or logistic support: R. Hudson, P.J. Stotz.

Collection and assembly of data: P.J. Stotz.


Ann Intern Med. 2015;162(5):325-334. doi:10.7326/M14-1189
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Background: Exercise reduces obesity and related glucose tolerance, but whether increasing exercise intensity offers additional benefit at fixed exercise amounts is unknown.

Objective: To determine the separate effects of exercise amount and intensity on abdominal obesity and glucose tolerance.

Design: 24-week, single-center, parallel-group trial from 2009 to 2013. (ClinicalTrials.gov: NCT00955071)

Setting: Kingston, Ontario, Canada.

Participants: 300 abdominally obese adults.

Intervention: Control (no exercise) (n = 75) or 5 weekly sessions of low-amount, low-intensity exercise (LALI) (180 and 300 kcal/session for women and men, respectively, at 50% of maximum oxygen consumption [V̇o2peak]) (n = 73); high-amount, low-intensity exercise (HALI) (360 and 600 kcal/session, respectively, at 50% of V̇o2peak) (n = 76); or high-amount, high-intensity exercise (HAHI) (360 and 600 kcal/session, respectively, at 75% of V̇o2peak) (n = 76). Daily unsupervised physical activity and sedentary time were measured by accelerometer.

Measurements: Waist circumference and 2-hour glucose level (primary outcomes) and cardiorespiratory fitness and measures of insulin action (secondary measurements).

Results: 217 participants (72.3%) completed the intervention. Mean exercise time in minutes per session was 31 (SD, 4.4) for LALI, 58 (SD, 7.6) for HALI, and 40 (SD, 6.2) for HAHI. Daily unsupervised physical activity and sedentary time did not change in any exercise group versus control (P > 0.33). After adjustment for age and sex in a linear mixed model, reductions in waist circumference were greater in the LALI (−3.9 cm [95% CI, −5.6 to −2.3 cm]; P < 0.001), HALI (−4.6 cm [CI, −6.2 to −3.0 cm]; P < 0.001), and HAHI (−4.6 cm [CI, −6.3 to −2.9 cm]; P < 0.001) groups than the control group but did not differ among the exercise groups (P > 0.43). After adjustment for covariates, reductions in 2-hour glucose level were greater in the HAHI group (−0.7 mmol/L [−12.5 mg/dL] [CI, −1.3 to −0.1 mmol/L {−23.5 to −1.5 mg/dL}]; P = 0.027) than the control group but did not differ for the LALI or HALI group versus the control group (P > 0.159). Weight loss was greater in all exercise groups than the control group (P < 0.001); however, reduction in body weight did not differ among the exercise groups (P > 0.182).

Limitation: The clinical importance of reducing 2-hour glucose level in nondiabetic adults remains undetermined.

Conclusion: Fixed amounts of exercise independent of exercise intensity resulted in similar reductions in abdominal obesity. Reduction in 2-hour glucose level was restricted to high-intensity exercise.

Primary Funding Source: Canadian Institutes of Health Research.

Figures

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Figure 1.

Study flow diagram.

HAHI = high-amount, high-intensity exercise; HALI = high-amount, low-intensity exercise; LALI = low-amount, low-intensity exercise.

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Figure 2.

Waist circumference and 2-h glucose level during the 24-wk study.

Data represent least-square means and were adjusted for age and sex; errors bars indicate 95% CIs. Analyses were done by using all randomly assigned participants. At baseline, waist circumference or 2-hour glucose level did no differ among groups. HAHI = high-amount, high-intensity exercise; HALI = high-amount, low-intensity exercise; LALI = low-amount, low-intensity exercise. Left. Waist circumference. At weeks 16 and 24, the reductions were greater in all exercise groups than in the control group (P < 0.001) but did not differ from each other (P > 0.10). Right. 2-hour glucose level. At week 16, there were no differences between the LALI or HALI and control groups (P > 0.10) or the HAHI and control groups (P = 0.07). At week 24, the decrease was greater in the HAHI group than the control (P = 0.03) and LALI (P = 0.04) groups. No significant changes were seen for the LALI or HALI groups compared with the control group (P > 0.10).

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Appendix Figure.

Cardiorespiratory fitness during the 24-wk study.

Data represent least-square means and were adjusted for age and sex; errors bars indicate 95% CIs. Analyses were done on an intention-to-treat basis. At baseline, there were no differences between groups. At weeks 4, 8, 16, and 24, the increase in V̇o2peak was greater for the HAHI group than the LALI (P < 0.001) and control (P < 0.001) groups. At weeks 16 and 24, the increase in V̇o2peak was greater for the HALI group than the control (P < 0.001) and LALI (P < 0.001) groups. The increase in V̇o2peak for the HAHI group was greater than the HALI group at 8, 16, and 24 weeks (P = 0.03, 0.002, and 0.03, respectively), with intention-to-treat. The number of participants at each time point is indicated. At weeks 4 and 8, participant data in the control group were not collected. HAHI = high-amount, high-intensity exercise; HALI = high-amount, low-intensity exercise; LALI = low-amount, low-intensity exercise; V̇o2peak = maximum oxygen consumption.

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