Green Tea & Fat Metabolism
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Green Tea Catechins & Fat Metabolism
Green Tea & Fat MetabolismMacKenzie StarkMacronutrient Metabolism12-6-12
The Obesity Epidemic Obesity is currently viewed as one of the most serious health problems of the 21st century.Obesity is a medical condition in which an individual has excess body fat in relation to lean body mass.Defined as having a BMI of 30 or higher.Associated with T2DM, CVD, hypertension, and certain cancers. Green Tea ComponentsDuring the past 10 years, green tea has been studied for its potential as a natural agent for weight loss.Green tea contains polyphenol components, also known as catechins.The most abundant catechin in green tea leaves is epigallocatechin gallate (EGCG). Researchers have proposed that EGCG may have an anti-obesity effect.
Fatty Acid SynthesisFatty acid synthesis is the creating of fatty acids from acetyl-CoA and malonyl-CoA precursors. Acetyl-CoA is carboxylated to malonyl-CoA by the enzyme acetyl-CoA carboxylase (ACC).Malonyl-CoA can then feed into the fatty acid synthase system.Series of enzymatic reactions occur and the end product is palmitic acid.Fatty acids are stored as triglycerides in adipose tissue.
Acetyl-CoA carboxylation to Malonyl-CoA
Fatty Acid Synthase System
The Effect of CatechinsThe exact mechanism of catechins on fatty acid synthesis is inconclusive.However, researchers have proposed that catechins have the ability to inhibit the action of ACC.This would reduce the production of malonyl-CoA.The reduction in malonyl-CoA would directly decrease fatty acid synthesisMalonyl-CoA is a highly regulated molecule in fatty acid synthesis, and it inhibits carnitine palmitoyl transferase I.Relieving inhibition of CPT1 allows more fatty acids to enter the mitochondrial matrix and effectively increases Beta-oxidation of fatty acids.
Clinical Trial 1This study consisted of 30 volunteers-15 were put in the experimental group and 15 in the control group.Between the ages of 20 and 50, with a BMI greater or equal to 24 kg/m2.Experimental group consumed two 325 mL of a green tea beverage each day containing 267 mg catechins and 18 g of inulin powder.Control group consumed two 325 mL of a green tea beverage each day containing 81 mg catechins. Each group ate three meals provided by the hospital, and all other foods and beverages that contained catechins, polyphenols or caffeine were prohibited. Study lasted eight weeks, where the first six weeks were the experimental weeks, and the last two weeks were a follow-up period. Body weight, BMI and fat mass were measured in each group at the third, sixth and eighth week. ResultsThere was a significant reduction in body weight, BMI and fat mass in the experimental group compared to the control group at the third and sixth week.These differences were maintained during the two week follow-up period.The mean BMI in the control group was 26.7 at baseline and remained the same after six weeks.The mean BMI of the experimental group was 27.3 at baseline and decreased to 26.6 after six weeks. Results show that catechin-rich green tea plus inulin may have beneficial effects in people who are overweight or obese.
Clinical Trial 2The second study consisted of 240 Japanese men and women with visceral fat-type obesity between the ages of 25 and 55.The control group received one 340 mL green tea beverage daily with 96.3 mg catechins and 75 mg caffeine. The experimental group received one 340 mL green tea beverage daily with 582.8 mg catechins and 72.3 mg caffeine. Dietary intake was not monitored, but food products and/or medications known to influence lipid or CHO metabolism were prohibited. The study started with a two week run in period and a 12 week treatment period. Each subject visited the medical institution at four week intervals to have their anthropometrics and biochemical labs recorded.
ResultsAfter the 12 week trial, the results showed a significant decrease in body weight, BMI, body fat ratio, body fat mass, waist circumference, and hip circumference in the experimental group.Lean body mass significantly increased over time.Total fat area, visceral fat are, and subcutaneous fat area all significantly decreased in the experimental group compared to the control group.The mean BMI decreased by 0.6 in the experimental group, and there was no change in BMI in the control group after 12 weeks. Results suggest that continuous ingestion of catechins in high amounts reduces body fat and might prevent obesity. Catechin/controlWeek 0Week 4Week 8Week 12Value at Week 12* Body weight (kg) Catechin73.3 (9.7)72.5 (9.8)72.2 (9.8)71.6 (9.8)- 1.7 (1.5)Control72.1 (10.0)71.9 (10.1)71.9 (10.2)72.1 (10.3)- 0.1 (1.7)BMI (kg/m2) Catechin26.9 (1.9)26.6 (1.9)26.4 (1.9)26.2 (1.9)- 0.6 (0.6)Control26.7 (2.1)26.6 (2.2)26.6 (2.2)26.6 (2.2)- 0.0 (0.6)Body fat ratio (% ) Catechin30.7 (6.4)30.0 (5.8)28.9 (6.3)28.3 (6.1)- 2.5 (3.3)Control30.7 (5.4)30.2 (5.7)29.2 (5.6)30.0 (5.6)- 0.7 (2.8)Body fat mass (kg) Catechin22.3 (4.6)21.6 (4.0)20.6 (4.1)20.0 (4.0)- 2.3 (2.6)Control22.1 (4.4)21.6 (4.7)20.9 (4.6)21.5 (4.7)- 0.5 (2.3)Lean body mass (kg) Catechin51.0 (9.4)50.9 (9.3)51.5 (9.8)51.6 (9.7)0.6 (2.3)Control50.1 (8.6)50.3 (8.6)51.0 (8.9)50.5 (8.8)0.4 (2.3)Waist circumference (cm) Catechin87.2 (5.2)86.3 (5.3)85.5 (5.5)84.7 (5.5)- 2.5 (2.2)Control86.5 (6.1)86.4 (6.5)86.6 (6.8)86.5 (6.7)0.0 (2.5)Hip circumference (cm) Catechin98.0 (4.7)97.2 (4.5)96.3 (4.4)95.7 (4.4)- 2.3 (2.0)Control97.2 (5.6)97.0 (5.9)97.1 (6.0)97.1 (6.0)- 0.1 (2.4)Total fat area (cm2) Catechin324.3 (79.3)308.4 (79.9)- 16.0 (46.6)Control315.8 (77.1)316.0 (79.0)0.1 (32.6)Visceral fat area (cm2) Catechin109.2 (42.3)98.9 (38.6)- 10.3 (23.3)Control107.7 (44.0)103.8 (38.9)- 3.9 (24.9)Subcutaneous fat area (cm2) Catechin215.2 (66.9)209.5 (66.3)- 5.7 (38.5)Control208.1 (60.7)212.1 (64.9)4.0 (24.8)DiscussionBoth studies suggested that green tea catechins ingested in high amounts increase fat loss in overweight or obese individuals.However, the exact mechanism regarding the effect of catechins on fat metabolism is inconclusive and further studies are needed. Several limitations to each study. The first study added inulin. Inulin is a naturally occurring soluble fiber. Inulin can give you a feeling of fullness and suppress your appetite. Could this account for the weight loss?Green tea contains caffeine, which has been studied for its effect on weight loss. Synergy effect?The dosage of catechins in the experimental groups was very high. Equivalent to 8-10 cups of green tea daily. Whats the best way to ingest high amounts of catechins? ConclusionCatechins found in green tea appear to aid in the reduction of fat.Green tea catechins appear to be safe, as no adverse reactions were seen in either study.A natural and effective supplement that can be used to support weight loss in overweight or obese individuals.Questions?