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Fixed exercise time, not intensity decreases abdominal fat; intensity required to improve glucose levels
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Abdominal obesity decreases with fixed amounts of exercise of any intensity level, but reductions in glucose levels appear to occur only when the intensity level is high, according to research published in the Annals of Internal Medicine.
“Higher intensity can be achieved simply by increasing the incline while walking on a treadmill or walking at a brisker pace,” Robert Ross, PhD, of the school of kinesiology and health studies, Queen’s University, Ontario, Canada, said in a news release. “Participants were surprised by how easy it was for them to attain a high intensity exercise level.”
Ross and colleagues, recruited 300 adults with abdominal obesity in a single-center, parallel-group, controlled trial between 2009 to 2013; 217 participants (72.3%) completed the intervention.
The researchers randomized patients to no exercise (controls) (n = 75) or five 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, or VO2 peak) (n = 73); high-amount, low intensity exercise (HALI) (360 and 600 kcal/session, respectively, at 50% of VO2peak) (n = 76); or high-amount, high-intensity exercise (HAHI) (360 and 600 kcal/session, respectively, at 75% of VO2peak) (n = 76). Daily unsupervised physical activity and sedentary time was calculated through accelerometer.
The investigators primarily looked for changes in waist circumference and 2-hour glucose levels. Cardiorespiratory fitness and insulin action served as secondary outcomes.
The mean exercise time for LALI was 31 minutes per session (standard deviation, 4.4), for HALI 58 minutes (SD, 7.6) and for HAHI 40 minutes (SD, 6.2). Compared with controls, no changes were seen in daily unsupervised physical activity and sedentary time in any exercise group.
Using a linear mixed model with adjustments for age and sex, reductions in waist circumference were greater with LALI (–3.9 cm; 95% CI, –5.6 to –2.3 cm), HALI (–4.6 cm; 95% CI, –6.2 to –3 cm) and HAHI (–4.6 cm; 95% CI, –6.3 to –2.9 cm) than with no exercise, but did not differ among intervention groups.
Greater decreases in 2-hour glucose levels occurred in the HAHI group (–0.7 mmol/L, or –12.5 mg/dL; 95% CI, –1.3 to –0.1 mmol/L, –23.5 to –1.5 mg/dL) compared with controls, with adjustments for covariates; however, the decreases did not differ in the LALI and HALI groups compared with controls.
All exercise groups demonstrated greater weight loss than the control group (P < .001), but reductions in body weight did not differ among exercise groups.
“Because approximately 45% and 60% of adult women and men are abdominally obese and at greater risk for diabetes … a sizeable proportion of the adult population would probably benefit from the exercise strategies studied,” the researchers wrote. – by Allegra Tiver
Disclosure: The researchers report no relevant financial disclosures.
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