The study, published in Obesity, reports that mice given EGCG in addition to a high-fat diet gained weight 45% more slowly than the control group of mice eating the same diet without EGCG.
In addition to lower weight gain, the researchers reported that mice fed the green tea supplement showed around a 30% increase in faecal lipids – suggesting that the EGCG limits fat absorption.
"Our results suggest that if you supplement with EGCG or green tea you gain weight more slowly," said research leader Joshua Lambert, who is assistant professor of food science in agricultural sciences at Penn State University, USA.
"There seems to be two prongs to this," explained Lambert. "First, EGCG reduces the ability to absorb fat and, second, it enhances the ability to use fat."
Green tea and EGCG
The majority of science on tea has looked at green tea, with benefits reported for reducing the risk of Alzheimer's and certain cancers, improving cardiovascular and oral health, as well as aiding in weight management.
Green tea contains between 30 and 40 per cent water-extractable polyphenols, while black tea (green tea that has been oxidized by fermentation) contains between 3 and 10 per cent. The four primary polyphenols found in fresh tealeaves are epigallocatechin gallate (EGCG), epigallocatechin, epicatechin gallate, and epicatechin.
Lambert and his team noted that several studies have shown that green tea, and its major polyphenolic component EGCG, may modulate body weight and fat levels. The new study examined the ability of EGCG to modulate fat absorption and BW gain in high fat-fed obese mice and sought to gain insight into the mechanisms of action.
Lambert and his colleagues supplemented obese mice with EGCG for 6 weeks, whilst on a high fat diet.
"There's no difference in the amount of food the mice are eating," said Lambert. "The mice are essentially eating a milkshake, except one group is eating a milkshake with green tea."
The research team reported that mice given EGCG with the high-fat diet reduced body weight gain by 44% compared to mice just given a high-fat diet.
“EGCG [also] caused a 29.4% increase in mean faecal lipid levels compared to HF mice. This increase suggests that EGCG decreases lipid absorption ... To our knowledge, this is the first demonstration of EGCG-induced changes in faecal lipid output by obese mice,” reported Lambert and his team.
They added that EGCG was also found to dose-dependently inhibit pancreatic lipase (PL) – an enzyme that is key to the breakdown and absorption of fat.
“We report for the first time that EGCG inhibited pancreatic lipase in a non-competitive manner with regard to substrate concentration,” said the researchers.
“These results suggest that EGCG may modify the active site of PL irreversibly, perhaps through some oxidative interactions with cysteine residues,” they suggested.
They concluded that treatment of high fat-fed obese mice with 0.32% EGCG can modulate body weight gain, “and these effects appear to be due in part to EGCG-mediated modulation of lipid absorption possibly via PL.”
Published online ahead of print, doi: 10.1038/oby.2011.139
“(−)-Epigallocatechin-3-gallate Inhibits Pancreatic Lipase and Reduces Body Weight Gain in High Fat-Fed Obese Mice”
Authors: K.A. Grove, S. Sae-tan, M.J. Kennett, J.D. Lambert