Regular consumption of green tea may have benefits for dieters. So far no large, conclusive studies have been done, and the few existing human studies have been equivocal. In fact, one study published in the 2004 British Journal of Nutrition suggests that green tea may actually hinder maintenance of a good weight after weight loss. But animal studies, in which variables like food intake and exercise levels can be tightly controlled, and a few human studies show several benefits.
May Promote Weight Loss
One study reported in the 2005 issue of Obesity Research looked at weight loss in overweight and moderately obese people. Researchers reduced the subjects' calorie intake, causing four weeks of weight loss followed by three months of weight management. They found that green tea that had been spiked with extra caffeine caused weight loss by burning fat. A green tea spiked with a low level of caffeine also helped with weight loss maintenance.
May Reduce Food Intake
An animal study reported in the 2000 issue of Endocrinology may help explain why green tea seems to help with weight loss. Researchers injected rats with pure green tea catechins and looked at the effects on their endocrine systems. They found that one of those catechins, epigallocatechin gallate, significantly reduced food intake. Though oral administration of EGCG didn't cause as great a result, these researchers propose that long-term oral use might also have benefits.
May Burn Fat
In another animal study reported in the November 2000 issue of American Journal of Clinical Nutrition, researchers again found that green tea extracts injected into rats caused weight loss. They suggest that these extracts may "stimulate thermogenesis and fat oxidation." In other words, they may help burn fat. However, this study found that the effect was short-lived. Within a week the rats adapted to the extract and needed a higher dose to get the same effects. When researchers stopped giving the rats the extract, the weight came back.
May Reduce Fat Gain
A 2003 Journal of Nutritional Biochemistry article suggests that green tea may even help slow expected weight gain. Rats were feed green tea along with a high-fat diet. The tea increased energy expenditure and suppressed the expected fat gain.
References
- "British Journal of Nutrition"; Effects of green tea on weight maintenance after body-weight loss; Eva M. R. Kovacs; 2004
- "Obesity Research"; Body Weight Loss and Weight Maintenance in Relation to Habitual Caffeine Intake and Green Tea Supplementation; Margriet S. Westerterp-Plantenga; 2005
- "Endocrinology"; Modulation of Endocrine Systems and Food Intake by Green Tea Epigallocatechin Gallate; Yung-Hsi Kao; 2000
- "American Journal of Clinical Nutrition"; Modulation of obesity by a green tea catechin; Yung-hsi Kao; November 2000
- "Journal of Nutritional Biochemisty"; Green tea reduces body fat accretion caused by high-fat diet in rats through β-adrenoceptor activation of thermogenesis in brown adipose tissue; J.J. Choo; Novemebr 2003
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