Green tea improves metabolic biomarkers, not weight or body composition: a pilot study in overweight breast cancer survivors

Background: Overweight status after breast cancer treatment may increase a woman's risk for recurrent disease and/or early onset cardiovascular disease. Green tea has been proposed to promote weight loss and favourably modify glucose, insulin and blood lipids. This pilot study tested the effect of daily decaffeinated green tea consumption for 6 months on weight and body composition, select metabolic parameters and lipid profiles in overweight breast cancer survivors. Methods: The effect of daily decaffeinated green tea intake on weight, body composition and changes in resting metabolic rate, energy intake, glucose, insulin, homeostasis model assessment - insulin resistance (HOMA-IR) and lipids was evaluated in overweight breast cancer survivors. Participants had a mean weight of 80.2 kg; body mass index (BMI) 30.1 kg m-2; and body fat 46.4%. Participants (n = 54) were randomised to 960 mL of decaffeinated green or placebo tea daily for 6 months. Results: Mean (SD) tea intake among study completers (n = 39) was 5952 (1176) mL week-1 and was associated with a significant reduction in energy intake (P = 0.02). Change in body weight of -1.2 kg (green tea) versus +0.2 kg (placebo) suggests a weight change effect, although this was not statistically significant. Decaffeinated green tea intake was associated with elevated high-density lipoprotein (HDL) levels (P = 0.003) and nonsignificant improvements in the HDL/LDL ratio and HOMA-IR (-1.1 +/- 5.9: green tea; +3.2 +/- 7.2: herbal). Conclusions: Intake of decaffeinated green tea for 6 months was associated with a slight reduction in body weight and improved HDL and glucose homeostasis in overweight breast cancer survivors.