Sixteen weeks of the green-tea-extract-and-exercise regimen also led to significant reductions in fasting blood sugar levels (17% reduction) and insulin levels (65% reduction), according to findings published in Molecular Nutrition Food Research .
On the other hand, green tea alone or exercise alone led to smaller changes in weight and health measurements, report researchers from Penn State's College of Agricultural Sciences.
“What is significant about this research is that we report for the first time that voluntary exercise in combination with green tea extract reduced symptoms of metabolic syndrome and diet-induced obesity in high-fat-fed mice more significantly than either treatment alone,” said Dr Joshua Lambert, associate professor of food science and lead researcher.
“The changes in body weight and body fat may result from increased fat metabolism and decreased fat synthesis. Green tea seems to modulate genes related to energy metabolism.”
The study adds to an ever-growing body of science supporting the potential benefits of green tea and its constituents, most notably EGCG (epigallocatechin gallate). To date green tea has been linked to a reduced risk of Alzheimer's and certain cancers, improved cardiovascular and oral health, as well as benefits in weight management.
Green tea contains between 30% and 40% of water-extractable polyphenols, while black tea (green tea that has been oxidized by fermentation) contains between 3% and 10%. Oolong tea is semi-fermented tea and is somewhere between green and black tea. The four primary polyphenols found in fresh tealeaves are epigallocatechin gallate (EGCG), epigallocatechin (EGC), epicatechin gallate (ECG), and epicatechin (EC).
While the Penn State study was performed with mice Dr Lambert said that people may realize similar benefits.
“I think we can make that leap,” he said. “When we put together our animal model experiments, we try to mimic the human situation as much as possible, so the dose of decaffeinated green tea that we used in this study is the equivalent of 8 to 10 cups of green tea a day, which is a lot for some people. But there are many people out there who are heavy, regular tea consumers.”
Dr Lambert and his team put lab mice on a high fat diet and randomly assigned them to decaffeinated green tea extract and voluntary running exercise separately or in combination for 16 weeks. Results showed that, in addition to the beneficial changes to body mass, fat mass, blood glucose and insulin levels, there were significant changes to the expression of genes related to fat and energy metabolism.
While the study’s findings are promising for people, Dr lambert cautioned that research needs to be done with humans to verify this.
“It looks promising for people, but somebody will have to do this experiment with people to definitively show that green tea and exercise together have a beneficial effect in humans,” he said.
The study was funded by the National Institutes of Health.
Source: Molecular Nutrition Food Research
Published online ahead of print, doi: 10.1002/mnfr.201300621
“Voluntary exercise and green tea enhance the expression of genes related to energy utilization and attenuate metabolic syndrome in high fat fed mice”
Authors: S. Sae-tan, C.J. Rogers, J.D. Lambert