I think we started hearing about green tea as a magical weight loss potion some time in the early ’90s. The exoticism of the Far East probably plays into it, as well as the fact that only around a quarter of Chinese people are overweight (in the UK we’re nearing two thirds [pdf]). Green tea likes to pop up on lists of things which remove “toxins”.

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I like green tea. It tastes really nice with lemon. It also makes me feel healthy and radiant, which I chalk up to the fact that I’ve internalised all the endless messages about its health benefits like an entranced toxin-filled sponge.

In 1989 Todd Heatherton and his colleagues at the University of Toronto ran an experiment [pdf]. They gave people who were on a diet a pill and they told them that it would make them feel a) hungry, or b) full. The pill was a placebo, a sugar pill, in both cases – but the people who thought they should be feeling hungry ate more, and the ones who thought they’d be full ate less. Our expectations of how we should feel have a pretty potent effect on how we actually feel.

Green tea is not immune from this effect. This is especially true if you have just woken up on January 1st and started drinking green tea as part of your New Lifestyle™ which also includes not drinking whisky before noon and going for jogs before 6am. Yes, you might be feeling better because of the green tea, but those other things are probably having an effect too.

Plot twist: I did some research and it turns out that hey, actually green tea does have an effect on weight loss! Sort of. Maybe.

Some kind people in the Netherlands did a meta review of the literature a couple of years ago and found that out of 11 (long-term, blind, placebo-controlled) studies, 8 found that green tea led to weight loss. To be fair, most of these were carried out with Asian participants, so there could be environmental or cultural factors at work. The results are also far from impressively unequivocal and we’re talking about a difference of 2kg here, not ten. Still, it’s somehow a lot better than I expected.

Apparently it’s not just the caffeine, either. The thing in green tea that’s thought to help with weight loss is catechin, which is an antioxidant. It’s also found in vinegar and cocoa, which explains things like “the chocolate diet” and “I always drink a spoon of vinegar before each meal, darling.

If you like drinking green tea, by all means keep at it. Drink it for the lovely taste, the break from your usual builder’s brew, for the delicious placebo effect, but really – don’t drink it to lose five stone in three days. It ain’t magic.