Both green tea and metformin are used as adjuvants to treat and prevent complications associated with obesity; however, studies comparing their action and interaction in non-diabetic overweight women have not been reported. Thus, the current study, published in Clinical Nutrition ESPEN,evaluated the effects of green tea extract and metformin, both individually and in combination, on type 2 diabetes risk factors in non-diabetic overweight women.
Methods of green tea and metformin study
A total of 120 overweight women were randomly assigned in a double-blind manner to 1 of 4 groups, 
as follows: control (n = 29; 1 g of cellulose), green tea (n = 32; 1 g of dry green tea extract), metformin (n = 28; 1 g of metformin), and green tea + metformin (n = 31; 1 g of dry green tea extract + 1 g of metformin). Each group took the indicated capsules daily for 12 weeks. Anthropometric measurements, body composition, and fasting blood samples were evaluated.
Results
Although no significant interactions were observed in glycemic control (p=0,07), the study found the following:
- Green tea in the absence of metformin reduced fasting glucose (-4.428 ± 2.00; p=0.031), but when combined the lowering effect was nullified.
- In contrast, metformin increased HbA1c concentration (0.048 ± 0.189%; p = 0.017) and also reduced body weight (-1.318 ± 0.366 kg; p = 0.034) and LM (lean mass) (-1.249 ± 0.310; p = 0.009).
- As for lipid parameters, green tea significantly reduced total cholesterol and LDL-c.
Conclusions
Green tea was superior to metformin in improving fasting glucose and lipid profile in non-diabetic overweight women.
