Green Tea for Weight Management
Tea, the most popular beverage, is consumed by two-thirds of the world’s population. Many health benefits have been related to drinking tea, including the benefit for weight management. Several human studies found that consumption of about 3–5 cups tea per day for several weeks showed a small reduction on weight or body mass index (BMI) and improved on metabolic biomarkers (1).
A randomized, double-blind trial was conducted in women with abdominal obesity (with a BMI ≥ 27 kg/m2 and a waist circumference ≥ 80 cm). These women were randomly assigned to either a high-dose green tea group (high-dose green tea extract - epigallocatechin gallate, EGCG, at a daily dosage of 856.8 mg, n=39) or placebo group (n=38) (2).
Significant weight loss, from 76.8 ± 11.3 kg to 75.7 ± 11.5 kg (p = 0.025), as well as decreases in BMI and waist circumference from 31.0 ± 3.8 kg/m2 to 30.6 ± 3.9 kg/m2 (p = 0.018) and 95.1 ± 9.6 cm to 92.8 ± 9.8 cm (p = 0.023), respectively, were observed in the treatment group after 12 weeks of high-dose EGCG treatment. There was also a trend of decreased total cholesterol, reaching 5.33%, and decreased LDL plasma levels. There was good tolerance of the treatment among subjects without any side effects or adverse events. This study showed that 12 weeks of treatment with high-dose green tea extract could result in significant weight loss, reduced waist circumference, and a consistent decrease in total cholesterol and LDL plasma levels in women with central obesity (2).
In a randomized controlled trial conducted in 35 subjects with obesity and metabolic syndrome, subjects were given 4 cups of water a day as a control group, 4 cups of green tea a day as the green tea group, and 4 cups of water plus 2 capsules of the green tea extract as the green tea extract group for 8 weeks. The tea and extract groups had similar dosing of epiogallocatechin-3-gallate (EGCG), the active compound in green tea (3).
The results showed that 4 cups of green tea beverage consumption or 2 capsules of the green tea extract per day could significantly decrease the body weight and BMI compared to those of control group (-2.5 ± 0.7 kg, p <0.01, and -1.9 ± 0.6, p < 0.05, respectively) over 8 weeks. Green tea beverage showed a decreasing trend in LDL-cholesterol and LDL/high-density lipoprotein (HDL) vs controls (p < 0.1). Green tea beverage also significantly decreased malondialdehyde and hydroxynonenals (MDA and HNE, oxidative stress markers) (-0.39 ± 0.06 µM, p < 0.0001) vs controls (3).
A 12- week clinical trial was conducted in which 120 (25 male, 95 female) healthy, overweight and obese persons with a BMI of 25–38 kg /m2 were divided into 2 groups. The study used a green tea formula containing 6 g of green tea powder in a meal providing 1800 kcal a day as the treatment group and a normal diet without green tea powder as a control group (4).
More weight loss was found in the treatment group than the control (6.8 vs 2.3 kg; p <0.001). Also, the treatment group had a greater change in total cholesterol (185.2 vs 215.2 mg/dL; p =0.011) and low-density lipoprotein cholesterol (106.7 vs 127.6 mg/dL; p< 0.005). Among completers only, the treatment group again lost more weight (6.8 kg; n=54 vs 0.8 kg; n=56; p=0.001) and had a greater reduced total body fat mass (7.6%; n=37 vs 0.5%; p=0.005). This study showed that the green tea meal replacement formula could result in a greater decrease in the body weight, fat mass, and waist circumference than the control group (4).
In a double-blind trial, Japanese men and women received 583 mg of tea catechins as the treatment group and 96 mg of tea catechins as the control group per day for 12 weeks. The subjects consumed one can (340 mL) of the test beverage each day for a 12-week period. The time of ingestion of the test beverage was not limited, but it was recommended that the subjects drink the test beverage within 1 hour of their evening meal (5).
Decreases in body weight (-1.7±1.5 vs -0.1±1.7 kg), body mass index (-0.6±0.6 vs 0.0±0.6), body fat ratio (-2.5±3.3 vs -0.7±2.8 %), body fat mass (-2.7±2.6 vs -0.5±2.3 kg), waist circumference (-2.5±2.2 vs 0.0±2.5 cm), hip circumference (-2.3±2.0 vs -0.1±2.4 cm) were found to be greater in the catechin group than in the control group. A greater decrease in systolic blood pressure (SBP) (-9 ± 12.1 vs -2.9 ±12.0 mmHg ) was found in the catechin group compared with the control group for subjects whose initial SBP was 130 mm Hg or higher. Low-density lipoprotein (LDL) cholesterol (-0.09 ± 0.49 vs 0.04 ±0.52 mM) was also decreased to a greater extent in the catechin group (5).
A typical cup of green tea usually contains 250–350 mg tea solids, of which 30–42% are catechins and 3–6% caffeine. The major active constituents of tea are catechins, and among them, EGCG is the most potent and much of the health effect of green tea is predominantly credited to it (6). The average daily intake of EGCG resulting from the consumption of traditional green tea can range between 90 and 300 mg, and may reach 860 mg (the high dose used in some human studies) in adults who consume large quantities of these drinks. These studies have shown that drinking green tea can help with weight management.
References:
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Konstantinidi, M., & Koutelidakis, A. E. (2019). Functional Foods and Bioactive Compounds: A Review of Its Possible Role on Weight Management and Obesity’s Metabolic Consequences. Medicines, 6(3). https://doi.org/10.3390/medicines6030094
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Chen IJ, Liu CY, Chiu JP, Hsu CH. Therapeutic effect of high-dose green tea extract on weight reduction: A randomized, double-blind, placebo-controlled clinical trial. Clin Nutr. 2016 Jun;35(3):592-9. doi: 10.1016/j.clnu.2015.05.003. Epub 2015 May 29. PMID: 26093535.
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Basu A, Sanchez K, Leyva MJ, Wu M, Betts NM, Aston CE, Lyons TJ. Green tea supplementation affects body weight, lipids, and lipid peroxidation in obese subjects with metabolic syndrome. J Am Coll Nutr. 2010 Feb;29(1):31-40. doi: 10.1080/07315724.2010.10719814. PMID: 20595643.
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Tsai ChH, Chiu WC, Yang NC, Ouyang CM, Yen YH. A novel green tea meal replacement formula for weight loss among obese individuals: a randomized controlled clinical trial. Int J Food Sci Nutr. 2009;60 Suppl 6:151-9. doi: 10.1080/09637480903136667. PMID: 19736596.
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Nagao T, Hase T, Tokimitsu I. A green tea extract high in catechins reduces body fat and cardiovascular risks in humans. Obesity (Silver Spring). 2007 Jun;15(6):1473-83. doi: 10.1038/oby.2007.176. PMID: 17557985.
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Khan N, Mukhtar H. Tea and health: studies in humans. Curr Pharm Des. 2013;19(34):6141-7. doi: 10.2174/1381612811319340008. PMID: 23448443; PMCID: PMC4055352.
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