Consumed for thousands of years, especially in Asia, tea leaves contain numerous active ingredients. The most important are catechins (polyphenols from the flavonoid family, recognised as antioxidants), L-theanine (an amino acid derived from glutamine) and theine (the same molecule as caffeine) (1).
There are, however, a wide variety of teas. What’s more, the way in which the leaves are prepared before preserving has a significant impact on the tea’s ultimate content of active ingredients (2).
Black tea leaves undergo oxidation which promotes a bitter taste, increases the content of theine but reduces that of catechins.
In contrast, green tea is exposed to heat as soon as it has been picked, which prevents oxidation of the leaves. Two methods are used for this: the Chinese method (in which the leaves are heated in a tank) and the Japanese method (in which the leaves are steamed, preserving the tea’s active ingredients even more).
These methods of preparation mean that green tea contains 15%-30% catechins (compared with an average 9% for black tea), of which 50% -75% are epigallocatechin gallate (EGCG), tea’s most potent compound (3).
Matcha, sencha, gyokuro, bancha and genmaicha are all varieties of green tea that contain high catechin levels.
Although the various health authorities in Europe do not currently recognise the efficacy of green tea for weight loss, numerous studies have been exploring this question for a number of years.
And their results have been consistent: visceral fat loss was greater in subjects who consumed catechins than in controls (4-6).
Other studies have investigated the moderating effects of caffeine and the role of ethnicity. One study published in the International Journal of Obesity concluded that drinks containing catechins or a mixture of caffeine and epigallocatechin gallate (ECGC) had a mildly positive effect in reducing weight and fat mass (7).
Interestingly, this study revealed that increased caffeine intake reduced the slimming effects of green tea. Ethnicity also seems to play a role, with green tea’s slimming benefits appearing to be more marked among Asian populations, though this needs further investigation.
However, it appears that the benefits of green tea alone are not enough to produce weight loss or reduce abdominal fat effectively; other measures are needed.
A key factor in losing weight, especially slimming down the tummy, is achieving the right calorie balance. Based on your basal metabolic rate and activity level, you need to work out the amount of calories you consume each day (check out our article How many calories should you eat and burn each day?).
To lose weight, you need to consume fewer calories than you burn; it’s as simple as that.
There are, however, a few measures that can help with this:
With its diuretic and draining effects, green tea offers some efficacy in aiding weight loss and supporting health. Drinking a lot helps to eliminate toxins from the body, hence green tea’s detox reputation – and all without consuming too much caffeine.
In addition, by filling up the stomach, green tea curbs hunger and thus helps to reduce the amount of food consumed.
Drinking green tea with lemon is an excellent choice as the lemon juice helps acidify the pH of the drink. This improves the body’s acid-base balance, which is great for the metabolism, and therefore, weight loss.
Nevertheless, it’s unrealistic to rely on green tea for rapid weight loss: no ‘quick fix’ approach to losing weight i effective over the long-term. Successful slimming requires a gentler, more measured approach.
Anytime! But ideally, before meals (breakfast, lunch and dinner) or when you’re feeling a bit peckish. Drinking green tea before a meal helps to reduce your appetite (by curbing hunger) and enables you to properly digest all the drink’s micronutrients.
As much as you want! 3 to 5 cups of green tea a day would seem to be a good basis for aiding weight loss through adequate hydration.
While it’s perfectly possible to drink green tea throughout the day, you can also take advantage of dietary supplements that contain green tea’s active ingredients in order to obtain their benefits at higher doses:
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