Improving Glycemic Control by Interrupting Sitting Time

Patients with type 2 diabetes may benefit more from interrupting sedentary periods with standing or light-intensity walking than from a structured exercise program, according to data published in Diabetologia.¹

The World Health Organization (WHO) physical activity guidelines recommend 150 minutes of moderate-to-vigorous physical activity per week for the prevention and treatment of type 2 diabetes.² Many people, however, are not meeting these standards, the researchers noted, indicating that a different approach to exercise may be beneficial.

For this randomized, crossover SIT-LESS 2 study (Effect of Sitting Less on Glucose Regulation in People With Diabetes Mellitus Type 2; ClinicalTrials.gov identifier: NCT02371239), the researchers evaluated the potential positive effects of a “sit less” program that involved replacing sitting time with standing and light-intensity walking in comparison with a conventional structured exercise regimen of the same energy expenditure.

The study included 14 men and 6 women (mean age: 63 years) with type 2 diabetes. Mean body mass index (BMI) was 30.5 kg/m², mean disease duration was 6 years, mean HbA1c was 6.7%, and mean fasting glucose was 7.88 mmol/L during screening. Fourteen patients were using glucose-lowering drugs, and 13 were using lipid-lowering drugs.

The participants were randomly assigned to 1 of 3 activity regimens—“sitting,” “exercise,” and “sit less”—under free-living conditions for 4 days followed by a 10-day washout period during which they resumed usual lifestyle habits.

The sitting regimen restricted participants’ walking and standing time to 1 hour per day each, with the remaining 14 hours spent sitting. The exercise regimen involved replacing about 1 hour per day of sitting time with supervised cycling on an ergometer at a research center in 20-minute bouts separated by 5 minutes of rest. The sit-less regimen required participants to replace approximately 5 hours per day of sitting with 2 hours of walking and 3 hours of standing. They were encouraged to break up sitting time every 30 minutes with short bouts of walking and standing throughout the day. Energy expenditure for the exercise and sit-less regimens were comparable for each participant.

The researchers controlled participants’ diet using their normal diet supplemented by prepacked meals based on their energy requirements for each regimen during the last 36 hours of each 4-day period.

A subcutaneous glucose monitor and blood glucose samples, collected 4 times daily, were used to measure participants’ glucose levels. Light-intensity walking was recorded using a diary and verified advanced accelerometry. The researchers also measured 24-hour glucose levels during the last day of each regimen. Glucose, insulin, and lipid levels were then taken between 8:30 a.m. and 9:30 a.m. after an overnight fast on the day following each regimen.

Results showed that incremental area under the curve for 24-hour glucose—the primary outcome—was lower during the sit-less regimen than during the sitting regimen (1263 ± 189 min × mmol/L vs 1974 ± 324 min × mmol/L; P =.002) but was similar between the sit-less and exercise regimens (1383 ± 194 min × mmol/L; P =.499).

Insulin resistance, as measured by HOMA2-IR, was not improved during the exercise regimen vs the sitting regimen (2.06 ± 0.28 vs 2.16 ± 0.26; P =.177). However, compared with both the exercise and sitting regimens, the sit-less regimen (1.89 ± 0.26) was associated with a reduction in insulin resistance (P =.0015 and P =.001, respectively).

“Although an approximate energy-matched intervention with structured exercise also displayed most of the beneficial effects of breaking up sitting time, the present study provides indications favoring the implementation of interventions targeting the breaking-up of sitting time over interventions involving structured exercise,” the researchers wrote. “Additionally, the more abrupt and prominent reduction in blood glucose in the structured exercise intervention is proposed to increase the risk of hypoglycemia.”

They noted, however, that this proof-of-concept study had a high volume of activity, and future long-term studies are necessary to “determine the volume of light-intensity activities that is feasible in daily life.”

Disclosures: The study received additional funding from Novo Nordisk BV (unconditional grant) and the Netherlands Cardiovascular Research Initiative: an initiative with support of the Dutch Heart Foundation (CVON2014-02 ENERGISE). The consumables for continuous glucose monitoring and glucose measurements were supplied by Medtronic and Roche. The researchers reported no conflicts of interest.

Reference

1. Duvivier BMFM, Schaper NC, Hesselink MKC, et al. Breaking sitting with light activities vs structured exercise: a randomised crossover study demonstrating benefits for glycaemic control and insulin sensitivity in type 2 diabetes. Diabetologia. 2016 Dec 1. doi:10.1007/s00125-016-4161-7 [Epub ahead of print].