Cardoso GA, Salgado JM, de Castro Cesar M, Donado-Pestana CM. The effects of green tea consumption and resistance training on body composition and resting metabolic rate in overweight or obese women. J Med Food. 2013;16(2):120-127.

Addressing the rising obesity rates, researchers have examined the effects of green tea (Camellia sinensis) on weight loss because of its thermogenic and antiobesity properties. Some investigators have reported enhanced thermogenic effects of green tea when combined with exercise; this association increases energy expenditure, which enhances metabolism and promotes weight loss.^1,2 These authors investigated the effects of green tea consumption combined with resistance training on the body composition and resting metabolic rate (RMR) in overweight and obese women.

Thirty-six women in Saõ Paulo, Brazil were recruited through brochures, newspaper announcements, and local television advertisements. The women were sedentary, aged 20 to 40 years, and had a body mass index (BMI) of 25-35 kg/m².

For 4 weeks before the intervention, the women ate 1,200 kcal daily, with green tea providing the only polyphenols in their diet. The authors determined that a 4-week period was needed for the metabolic adaptation of the women. After that time, say the authors, any weight loss would be attributed to green tea consumption. The women were then divided into 4 groups: group 1 (green tea), group 2 (placebo), group 3 (green tea + resistance training), and group 4 (placebo + resistance training).

At that time and after 8 weeks of study intervention, the following were measured: biochemical variables, body composition, and RMR. For groups 3 and 4, a one-repetition maximum (1RM) was determined at baseline. During the 8 weeks, all women consumed 20 g of either green tea or placebo daily (10 g at 10 a.m. and 10 g at 4 p.m.) diluted in 200 mL of ice water.

The green tea and placebo were donated by Sanavita Industry in Piracicaba, São Paulo, Brazil. The study product contained powdered green tea, orange (Citrus sinensis) pulp, vitamin C, zinc, selenium, lemon (Citrus × limon) flavor, chlorophyll dye, and sucralose. Nutritionally, the product consisted of an energy value of 30 kcal (126 kJ); 7.5 g of carbohydrates; 15 mg of sodium; 2.1 mg of zinc; 13.5 mg of vitamin C; 10.2 mg of selenium; and 160 mg of total polyphenols. A 10-g portion of green tea contained 20 mg of caffeine. The placebo had the same nutritional composition and the same ingredients, except for the green tea.

Three times weekly, the women in groups 3 and 4 completed a resistance training program―3 sets of 10 repetitions of 10 exercises, with 60 seconds of rest between the repetitions. The women drank the green tea or placebo 10 minutes before each training session.

The authors report that in group 1, body mass, BMI, waist circumference, and body fat mass and percentage decreased, while the lean mass increased slightly. The subjects in group 1 lost an average of 5.7 kg (12 lbs 9 oz) (7.8%), which is probably due to the thermogenic effects of green tea,³ suggest the authors. The decreased body fat and increased lean body mass "can be attributed to increased mobilization of body fat as a source of energy, which preserves lean body mass," write the authors, noting that these findings are consistent with a study reporting that both fat oxidation and energy expenditure increased due to the bioactive compounds in green tea.⁴

Group 2 showed no improvement in any anthropometric parameter.

Group 3 showed no change in body weight or BMI; however, those subjects saw a significant decrease in waist circumference and body fat mass and percentage (P<0.05), and a significant increase in lean body mass (P<0.05). These findings, say the authors, were "due to adaptation to resistive exercise."⁵

Group 4 showed no changes in body weight or BMI; those subjects improved in the other variables, but not significantly.

The RMR decreased significantly in groups 1 and 2 (P<0.05), while groups 3 and 4 saw significant increases in RMR (P<0.05). In group 1, the RMR for body mass did not change; and in group 2, a measurable, but not significant, decline was observed. The RMR for body mass in groups 3 and 4 increased significantly, with the greatest increase seen in group 3 (P<0.05).

Groups 3 and 4 were the only groups that showed changes in the biochemical variables. Although triacylglyceride (TAG) levels decreased in both groups, the decrease was significant (P<0.05) only in group 3. The group 3 TAG levels decreased 8.7% more than in group 4. The authors attribute this reduction to the significant loss of body fat influenced by resistance training and green tea consumption. The authors cite an earlier study reporting that green tea catechins modulate the effects of the sympathetic nervous system on the oxidation of lipid deposits in a way superior to that of exercise alone.⁶ This would explain the greater decrease in TAG levels in group 3 versus group 4.

The subjects in groups 3 and 4, who completed the resistance training program, showed increased muscle strength (P<0.05), with those in group 3 showing the greatest improvement.

The authors conclude that, "Green tea promoted changes in body composition, weight loss, the maintenance of lean body mass, loss of body fat, decreased waist circumference, and lowered body fat percentage." When accompanied by resistance-training exercises, green tea consumption resulted in decreased waist circumference, body fat mass and percentage, and TAG levels, as well as gains in lean body mass and strength.

―Shari Henson

References

¹Murase T, Haramizu S, Shimotoyodome A, Tokimitsu I, Hase T. Green tea extract improves running endurance in mice by stimulating lipid utilization during exercise. Am J Physiol Regul Integr Comp Physiol. 2006;290(6):R1550-R1556.

²Venables MC, Hulston CJ, Cox HR, Jeukendrup AE. Green tea extract ingestion, fat oxidation, and glucose tolerance in healthy humans. Am J Clin Nutr. 2008;87(3):778-784.

³Shixian Q, VanCrey B, Shi J, Kakuda Y, Jiang Y. Green tea extract thermogenesis-induced weight loss by epigallocatechin gallate inhibition of catechol-O-methyltransferase. J Med Food. 2006;9(4):451-458.

⁴Dulloo AG, Duret C, Rohrer D, et al. Efficacy of a green tea extract rich in catechin polyphenols and caffeine in increasing 24-h energy expenditure and fat oxidation in humans. Am J Clin Nutr. 1999;70(6):1040-1045.

⁵Evans WJ, Cannon JG. The metabolic effects of exercise-induced muscle damage. Exerc Sport Sci Rev. 1991;19:99-125.