Study: Exercise 'snacking' helps control blood sugar
BRISTOL, England — New research published in Diabetologia, the journal of the European Association for the Study of Diabetes, found that brief bursts of intense exercise before meals — termed exercise "snacking" by the study authors — helps control blood sugar in people with insulin resistance more effectively than one daily 30-minute session of moderate exercise.
"The notion of doing small amounts of interval exercise before meals is a unique and very important feature of this study," stated Monique Francois, co-author of the study. "Sustained hyperglycaemia following meals is an important feature of insulin resistance. Reducing these post-meal spikes is important for reducing the risk of developing Type 2 diabetes and its associated complications," she said. "Dosing these small amounts of high intensity exercise before meals, particularly breakfast and dinner, may be a more time efficient way to get exercise into people's day, rather than devoting a large chunk of the day."
The participants completed three separate exercise interventions in random order. Measures were recorded across 3 days with exercise performed on the middle day, as either: (1) traditional continuous exercise (CONT), comprising one 30-minute moderate-intensity (60% of maximal heart rate) session of incline walking before dinner (evening meal) only; (2) exercise snacking (ES), consisting of 6 one-minute intense (90% maximal heart rate) incline walking intervals finishing 30 minutes before breakfast, lunch and dinner, with one minute slow walking recovery time after each minute of intense exercise; or composite exercise snacking (CES), encompassing 6 one-minute intervals alternating between walking and resistance-based exercise, with a one-minute slow walking recovery minute after each minute of exercise, again finishing 30 minutes before breakfast lunch and dinner. ES and CONT were matched for energy usage, whereas ES and CES were matched for time, but CES provided a brief workout for all of the body's major muscle groups across the day. Meal timing and composition were the same for all three exercise interventions and monitored using diet records, daily verbal discussion and dietary analysis software.
Exercise 'snacking,' whether before meals or not, provides breaks in sedentary time, and thus may be important for public health. In this study, 30 minutes of moderate-intensity exercise did not improve blood-sugar control, whereas distributing the same volume of exercise as three brief pre-meal HIT 'exercise snacks' resulted in a mean 12% reduction in the average post-meal glucose level, the mean across the three meals, an effect that was also sustained across the subsequent day. Walking-based ES and combined-exercise CES snacks improved blood-sugar control similarly, and both forms of exercise involved similar levels of exertion.
While acknowledging that further work is required to determine the clinical significance of their study, the authors reported their work adds to the recent interest in 'accumulating physical activity' as brief, repetitive bouts of intense exercise — as opposed to a single, prolonged, continuous exercise session — to prevent cardiometabolic disease. Many international guidelines prescribe exercise to maintain health — for example 30 minutes of moderate exercise 5 times a week — but such regimens still leave many people with prolonged sedentary time or inactivity, which has already been highlighted in previous research as harmful to health. Previous research also has shown more frequent breaks in sedentary time are beneficial for waist circumference, blood-glucose control and other metabolic parameters.
"We found exercise snacking to be a novel and effective approach to improve blood=sugar control in individuals with insulin resistance," Francois said. "Brief, intense interval exercise bouts undertaken immediately before breakfast, lunch and dinner had a greater impact on post-meal and subsequent 24-hour glucose concentrations than did a single bout of moderate, continuous exercise undertaken before an evening meal. The practical implications of our findings are that, for individuals who are insulin resistant and who experience marked post-meal increases in blood glucose, both the timing and the intensity of exercise should be considered for optimising glucose control."
The study used a crossover design, meaning that each participant acts as their own control, and questions can be answered with a much smaller number of participants. Nine individuals (i.e., two women, seven men) were recruited. All had blood test results showing insulin resistance, were not on cardiovascular or diabetic medication, were ages 18 years to 55 years (i.e., mean age of 48 years) and had a mean BMI of 36 kg/m2. They included two newly diagnosed Type 2 diabetics only detected as part of the screening.