Tea -- Camellia sinensis -- is rich in catechins, polyphenols that are natural antioxidents. A number of animal studies show the preventive effects of green tea polyphenols against obesity. A recent analysis of 11 human trials with green tea preparations reported a 1.31 kilogram average body weight loss in intervention groups compared to control groups.
Approximately 34 percent of adults in the United States are classified as obese. Obesity is a risk factor for metabolic syndrome. The most effective way to deal with the development of obesity and metabolic syndrome is lifestyle change, Lambert explained, adding that if people really want to lose weight, they need to exercise more to burn more calories, and they need to eat less.
"But our findings suggest that green tea in the absence of caffeine can enhance the effects of exercise," Lambert said. "The mice that exercised and had decaffeinated green tea extract had a more significant change in body weight, and they had better outcomes as far as lower blood glucose and lower plasma insulin levels. It looks like a combination of exercise and decaffeinated green tea enhances the body's ability to use energy that is taken in."
Decaffeination may not be crucial to the study, Lambert noted, but he did not want the presence of caffeine in the tea to blur the results. Researchers focused on decaffeinated green tea because the literature shows that caffeine has a stimulatory effect. If mice or people ingest caffeine, it increases their basal metabolic rate and plays a role in increasing energy utilization and decreasing body weight.
Also, because a segment of the population remains skeptical of caffeine's effect on health and avoids it, Lambert eliminated it from the research.