Many news articles and weight loss blogs have been reporting on green tea as the miracle supplement for fat loss; are their reports based on hard science, or just supplemental fluff? If it does work, is it best to use caffeine containing green tea or is a decaf version okay to use?
A recent meta-analysis study set out to answer these questions by analyzing the numerous studies published to date. After pooling the data and crunching the numbers, the scientists confirmed that green tea, especially caffeine containing green tea, does cause statistically significant weight loss! Let’s go through a couple of the studies evaluated to see just how much weight loss can be expected. (Am J Clin Nutr 2009 November)
In a randomized, controlled study on overweight adults, the subjects were given 1900 mg of green tea catechins (compounds believed to provide the majority of the benefit) for 90 days. In this study, only caffeinated green tea was given and each daily dose of green tea contained 400 mg of caffeine. At the end of the 90 day study, the average weight loss was 2.64 pounds and ¾ of one inch around the waist. Not too shabby considering that no changes were made to diet or activity! (Obesity, August 2009)
Another study, performed in type II diabetics, tested 582 mg of green tea catechins for 12 weeks. Not only did the green tea decrease abdominal fat, a type of fat that is especially toxic to diabetics, but it also restored the pancreases ability to make insulin, which is often decreased in late diabetes. In addition, a significant increase in adiponectin, a hormone that decreases insulin resistance, was also noted. Finally, it is worthwhile to note that there was also a decrease in hemoglobin a1c, a measure of blood sugar control. (Obesity, 2009, February 17(2):310-7)
These are just a couple interesting studies on green tea for weight loss, many more have been published showing equal or more impressive results. Green tea, even in high doses, has been shown to be safe, even healthy to take, over long periods of time. Although the decaf version of green tea does provide benefits to weight loss, the caffeinated version does appear to be superior.