Researchers have suggested that brief bursts of intense exercise before meals helps control blood sugar in people with insulin resistance more effectively than one daily 30-minute session of moderate exercise.
The study used a cross-over design, meaning that each participant acts as their own control, and questions can be answered with a much smaller number of participants.
Nine individuals (2 women, 7 men) were recruited. All had blood test results showing insulin resistance, were not on cardiovascular or diabetic medication, were aged 18-55 years (mean age 48), and had a mean BMI 36 kg/m2. They included two newly diagnosed type 2 diabetics only detected as part of the screening.
The participants completed three separate exercise interventions in randomised order. Measures were recorded across 3 days with exercise performed on the middle day, as either: (1) traditional continuous exercise (CONT), comprising one 30 min moderate-intensity (60 per cent of maximal heart rate) session of incline walking before dinner (evening meal) only; (2) exercise snacking (ES), consisting of 6×1 min intense (90 per cent maximal heart rate) incline walking intervals finishing 30 min before breakfast, lunch and dinner, with one minute slow walking recovery time after each minute of intense exercise; or composite exercise snacking (CES), encompassing 6X1 min intervals alternating between walking and resistance-based exercise (with a one-minute slow walking recovery minute after each minute of exercise), again finishing 30 min 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.
Female participants completed the trials in the early follicular phase of their menstrual cycle (across three separate cycles), whereas male participants had a minimum of 7 days between trials.
The researchers found that the ES and CES routines controlled blood sugar more effectively than the CONT routine, particularly 3-h post-meal glucose following breakfast (17 per cent reduction compared to no exercise) and dinner (13 per cent reduction compared to CONT). Across the day this represented a 12 per cent reduction in mean post-meal blood glucose concentration. The effect of the pre-lunch ES on blood glucose levels after lunch was unclear. Moreover, the reductions in blood glucose with ES compared to CONT persisted for a further 24 hours across the day following exercise.