Health effects of green tea catechins in overweight and obese men: a randomised controlled cross-over trial

Randomized controlled cross-over trial in sedentary, non-smoking overweight or obese men aged 40 to 69 years with BMI 28 to 38 kg/m2. Participants were studied at the Colworth Laboratory in the UK, with assessments at baseline and 6 weeks across two treatment periods.

Decaffeinated green tea extract (DGT; Sunphenon 90LB) was given orally as 530 mg per capsule, two capsules per day, taken 1 hour before breakfast and 1 hour before the evening meal for 6 weeks. The active supplement contained at least 75% catechins and less than 1% caffeine; placebo was used in a randomized cross-over design.

Green tea catechin supplementation increased circulating and urinary catechins, confirming absorption, but did not lower blood pressure or improve metabolic biomarkers over 6 weeks. Plasma EGCG was detectable after DGT treatment at a mean of 98 ng/ml, while baseline levels were undetectable; urinary EGC increased 28-fold and 4'-O-methyl EGC increased 34-fold in the DGT group. A period-by-treatment interaction suggested less weight gain in the first intervention period: body-weight change was -0.64 kg with DGT versus +0.53 kg with placebo, P=0.025. LDL-cholesterol decreased with DGT and increased with placebo after outlier removal, P=0.04, but other metabolic outcomes were not significantly affected; no robust genotype-by-treatment effects were seen.

The trial was short and included only middle-aged men, limiting generalizability. The crossover design showed a period-by-treatment interaction, and the weight and LDL findings were secondary or sensitivity-dependent rather than consistent primary effects. The sample was modest and not all randomized participants completed both phases, reducing precision for subgroup and genotype analyses.