Update on the Evaluation of the Anti-Obesity Effect of Green Tea (Camellia sinensis)

Objective: Obesity is a worldwide rising risk factor for numerous incommunicable illnesses. The most common interventions have been ineffective from a public health perspective. Green tea (Camellia sinensis) seems to be an effective well-known alternative but there is a need to see the most updated and reliable information on the matter. The study aimed to verify how effective is green tea as reductor of human body mass index (BMI). Methods: This meta-analysis reviewed recent controlled randomized trials on the effect of catechin and caffeine in the BMI of adult male and female subjects. The analysis did not include studies including alternative therapies or drugs potentially affecting BMI. The studies presented the quantity of catechin and caffeine (mg). Body mass index and waist circumference were measured before and after the interventions. The trials lasted two to eight months, depending on the study designs. Results and Conclusion: Five studies met the criteria for the current analysis. In one study, the subjects took oral capsules of green tea extract (379mg). Overall, daily doses of catechin varied from 208-1200mg, and caffeine from undetectable levels to 480mg (the tea products were either enriched, capsules or canned with known levels). All showed reduction in body weight, the average BMI reduction was 0.68 kg/m2, and waist circumference was 1,5cm. There was a direct relationship between the concentration of catechin and reduction of BMI, but the BMI appeared to drop to a certain threshold of "optimal" weight, close to values considered as normal weight by the World Health Organization (WHO). There were few cases suggesting abdominal discomfort, but there they did not require additional treatment or hospitalization. Green tea consistently showed ability to reduce weight to a less risky level for health. Yet, it is now necessary to develop dose-response models for its active compounds and clarify the dynamics of the dosage over time. Furthermore, green tea is perhaps more effective in synergy with wellknown methods to maintain or reduce weight, such as balanced diets or physical exercise.