“Exercise Snacking” Aids Glycemic Control
Short bursts of intense exercise—“exercise snacks”—may prove an effective alternative to a prolonged period of continuous, moderate exercise for improving glycemic control in insulin-resistant individuals, a new study finds.
A team of researchers from the University of Otago in Dunedin, New Zealand, assigned 9 individuals with insulin resistance to 3 pre-meal exercise interventions in randomized order. The participants performed 30 minutes of continuous, moderate-intensity incline walking; “exercise snacking” consisting of 6 1-minute intervals of intense incline walking; or composite exercise snacking consisting of 6 1-minute intervals of alternating between walking and resistance training.
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The investigators found that exercise snacking reduced mean 3-hour postprandial glucose concentration following breakfast, but not following lunch. Exercise snacking was more effective than continuous, moderate-intensity incline walking in reducing mean 3-hour postprandial glucose concentration following dinner. Exercise snacking also reduced 24-hour mean glucose concentration by 0.7+0.6mmol/L (P=0.01), a reduction which continued for the next 24 hours. Alternating between walking and resistance training was as effective for improving glycemic control as exercise snacking, the authors note.
“These findings mostly signify that some short bouts of reasonably intense exercise before meals help to blunt the problematic blood glucose surges following meals, presumably because muscles are rendered more sensitive to taking up glucose at this time,” says Jim Cotter, BSc, BPhEd, MPhEd, PhD, associate professor at the School of Physical Education at the University of Otago, and co-author of the study.
These are acute effects, “but they persist throughout at least some of the following day, and are valuable irrespective of any concomitant adaptions that will be taking place—increased mitochondrial volume, increased glycogen storage capacity, for example,” says Cotter, who notes that the study was conducted with a small, at-risk population, and that determining whether this type of exercise is as effective before lunch has yet to be done.
When prescribing exercise to insulin-resistant patients, primary care physicians must consider factors such as intensity, timing, and frequency, adds Monique Francois, teaching fellow and research assistant at the University of Otago, and study co-author.
“Exercise on top of an active lifestyle needs to be more intense than normal when walking and moving around,” says Francois. “We need to challenge the body a little, promoting adaptations. Especially if patients don’t have time, high-intensity exercise can be performed in about half the amount of time, with similar or greater benefits than low-to-moderate exercise.”
In terms of timing, “exercise spread across the day reduces sedentary time, and [when] spread before meals, particularly reduces blood-glucose spikes after meals, and controls blood glucose across the day,” she adds.
Francois M, Baldi J, et al. ‘Exercise snacks’ before meals: a novel strategy to improve glycaemic control in individuals with insulin resistance. Diabetologia. 2014.