Exercise: Do Intensity and Duration Matter? | Journal Scan

Study Questions:

What are the separate effects of habitual exercise, differing in amount and intensity, on abdominal obesity and glucose tolerance?


This was a 24-week, single-center, parallel-group, randomized, controlled trial conducted between 2009 and 2014. Participants were randomized to one of the following groups: control (no exercise) or 5 sessions per week of low-amount, low-intensity exercise (LALI; 180 and 300 kcal/session for women and men, respectively); high-amount, low-intensity exercise (HALI; 360 and 600 kcal/session for women and men, respectively); or high-amount, high-intensity exercise (HAHI; 360 and 600 kcal/session for women and men, respectively). Participants performed walk/jog exercise. Primary outcome measures were waist circumference at 8, 16, and 24 weeks; and 2-hour glucose level, which was measured in response to a 2-hour, 75-g oral glucose tolerance test between 36 and 48 hours after the last exercise session, at baseline and at 16 and 24 weeks.


A total of 217 participants (72.3%) completed the intervention. In analyses adjusted for age and sex, reductions in waist circumference were greater in LALI (-3.9 cm [95% confidence interval (CI), -5.6 to -2.3 cm]; p < 0.001), HALI (-4.6 cm [95% CI, -6.2 to 3.0 cm]; p < 0.001), and HAHI (-4.6 cm [95% CI, -6.3 to -2.9 cm]; p < 0.001) groups, compared to the control group. However, there were no differences among the exercise groups (p > 0.43). Reductions in 2-hour glucose level at 24 weeks were greater in the HAHI group than the control or LALI groups.


Exercise consistent with current guidelines is associated with significant reduction in abdominal obesity, independent of exercise intensity. However, only high-intensity exercise was associated with reduction in 2-hour glucose level.


This is an important study that provides useful information for clinicians identifying strategies for weight loss for obese adult patients. Exercise is associated with substantial reduction in waist circumference, independent of exercise intensity. It is intriguing that the benefit in reduction of 2-hour glucose level was only seen in the higher-intensity exercise group. As the authors acknowledge, the study was conducted ‘under ideal circumstances with motivated adults who were supervised during all exercise sessions.’ The results may be less encouraging in real-world settings.

Clinical Topics: Diabetes and Cardiometabolic Disease, Prevention, Sports and Exercise Cardiology, Exercise

Keywords: Walking, Exercise, Obesity, Obesity, Abdominal, Waist Circumference, Outcome Assessment (Health Care), Jogging, Metabolic Syndrome X, Primary Prevention, Glucose Tolerance Test, Glucose, Weight Loss, Weight Reduction Programs, Control Groups

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