Weight loss tea - does it work?

Compared with working up a sweat doing regular exercise, carefully planning out a balanced diet or swallowing supplements, sipping tea is a much more palatable option for losing weight. But can drinking a couple of cups of weight-loss tea every day really help you shed the kilos? We look at the evidence.

Labelled variously as 'slim', 'slender', 'body shape' or 'diet' tea, weight loss teas are widely available online and through retailers including supermarkets and chemists. But despite their popularity, a search of the medical literature turns up little in the way of published research on their effectiveness for weight loss (green tea aside).

So can they help you lose weight? We put this question to three experts:

Weight loss tea products contain a veritable smorgasbord of botanical ingredients, including a range of different tea leaves, herbs, spices and concentrated herbal extracts. We've listed some of the more common ones below.

Many have a long history of traditional use and are thought to have a variety of benefits , but in most cases more evidence is needed to support their effectiveness. For weight loss specifically there's little published evidence to support their use – at best, more definitive clinical trials are required before conclusions can be drawn.

Camellia sinensis (green tea) contains caffeine as well as compounds known as catechins. These are both thought to assist with weight loss by helping to increase energy expenditure (metabolism).

There have been a number of systematic reviews of studies focusing on green tea and weight loss. Their conclusions indicate a modest - but not always statistically significant - positive effect for some groups of people, which suggests that more research is needed.

Cinnamon - specifically the extracts of some cinnamon species - has been found to help improve blood sugar control and may be useful in the prevention and treatment of diabetes, according to a number of clinical investigations, but further trials are needed to establish its efficacy.

Dandelion contains chemicals that may increase urine production, but we could find no evidence to support its use for weight loss.

Fennel is used to help with various digestive problems including bloating, stomach upset and indigestion, but more evidence is needed to determine how effective it is for these uses.

Garcinia Cambogia contains the chemical hydroxycitric acid. It's suggested that this may help with weight loss by preventing fat storage and controlling appetite, although the evidence for this is inconclusive.

Hawthorn, also known as Crataegus pinnatifida, has been found to reduce the symptoms of heart failure and lower blood pressure in some human studies, but not others. Animal studies have also found it lowers blood cholesterol levels, but more research is needed.

Peppermint has been used in traditional medicine in many parts of the world to relieve indigestion. There's some evidence to suggest that taking peppermint oil orally reduces stomach pain, bloating, gas, and bowel movement frequency in people with Irritable Bowel Syndrome.

Senna - also known as Cassia Angustifolia - has a proven laxative effect and is used to treat constipation.

Yerba mate is a plant-based source of caffeine, which is a stimulant and is reported to be beneficial for weight loss due to its impact on increasing metabolic rate, but more evidence is needed to rate its effectiveness for this use.

Are weight loss tea products safe?

Weight loss teas are generally considered to be relatively low-risk, but some botanical ingredients can cause harm by themselves and also by interacting with conventional medicines.

Yerba mate, for example, can interact with stimulant drugs such as amphetamines and ephidrine, potentially resulting in increased heart rate and high blood pressure, so shouldn't be taken together. And people with gastrointestinal conditions such as ulcerative colitis or Crohn's disease should avoid using senna.

Either way, it's a good idea to check what's in the tea, just in case.

Consumers should be confident that the products they buy are safe and do what they say they're going to do – and regulation is necessary to achieve this. But we're concerned that weight loss teas fall into a grey area at what's known as the food-medicine interface, so aren't being suitably classified or regulated. And we're not the only ones.

"These types of products fall within a grey regulatory area, unfortunately, and companies are getting away with making claims that have little supporting evidence," says Professor Harvey.

Cancer Council NSW (CCNSW) has long been concerned about the potential impact that unsubstantiated health claims can have on people's food choices and ultimately their health.

Clare Hughes, CCNSW nutrition manager, tells us, "We are increasingly seeing claims about products that fall into that grey area between foods and therapeutics. In some cases it's food products that appear to be making therapeutic claims. In others, it's the form of the product – a pill or a powder for example – that suggest the product could be a complementary medicine, not a food. And sometimes the product is an ingredient that could go into a food or therapeutic good."

Regulation around claims for both food and complementary medicines needs to be strengthened so that companies can't exploit grey regulatory areas. If a product doesn't work or causes a problem it should be clear who consumers need to complain to.

Weight loss teas need to be classified as either food or medicine and regulated accordingly. We've written to the ACCC asking them to address this regulatory loophole.

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