High-intensity interval walking in combination with acute green tea extract supplementation reduces postprandial blood glucose concentrations in physically inactive participants.

Diet and exercise are foundational strategies to achieve blood sugar balance, but there are a variety of ways to implement both of these. Short bursts of high-intensity interval training or interval walking have shown benefits for glycemic control. Dietary supplements, including green tea catechins, have also shown promise in supporting blood sugar balance. 

In a double-blind crossover trial, researchers examined the effect of interval walking, and the additive effect of green tea extract, on glycemic control. Twelve young adults (aged 22 1) participated in the study. All participants were overweight and considered to be “physically inactive,” meaning they exercised less than 150 minutes per week at moderate intensity or less than 75 minutes a week at vigorous intensity.

Methods

On test days, participants arrived in a fasting state and were challenged with a 2-hour oral glucose tolerance test (OGTT) after one of 3 trial conditions: resting conditions (REST), acute exercise with green tea extract (EX-GTE), and acute exercise with placebo (EX-PLAC). Acute exercise consisted of 6 x 1-minute bursts of brisk walking alternating with 1-minute bursts of slower walking.

Participants in the EX-GTE group took one capsule of decaffeinated green tea extract powder (EGCG Green Tea Extract, Now Foods, Bloomingdale, IL) one hour before breakfast, lunch, and dinner on the day before the trial and one hour before the OGTT on the trial day. Each 400-mg capsule contained 320 mg of catechins (98% total polyphenols, 80% catechins, 50% EGCG).

Exercise and green tea extract may improve glycemic control.

Results

When compared with the REST condition, there was an approximate 9.4% reduction of glucose area under the curve with EX-GTE. This effect was considered to be “most likely” beneficial. Also compared with the REST condition, EX-GTE decreased peak glucose by approximately 9.8%, which was considered to be “very likely” beneficial. When compared with EX-PLAC, there was also a “very likely” beneficial effect of EX-GTE on glucose area under the curve. The difference between the REST condition and EX-PLAC on glucose area under the curve and peak glucose was unclear. 

Conclusions

The main finding of this study was that interval walking alone did not influence the glycemic response to a 2-hour OGTT, but the combined effect of walking and green tea extract had a beneficial impact on glucose area under the curve and peak glucose concentration. 

Bulmer, J.M., McBain, T.R., & Peart, D.J. (2018). High-intensity interval walking in combination with acute green tea extract supplementation reduces postprandial blood glucose concentrations in physically inactive participants. Nutrition and Health, 24, 193-198.