Green Tea

Green tea is made from the leaves of Camellia sinensis, the same plant used to produce black and oolong tea. The difference lies mainly in how the leaves are processed. Green tea leaves are heated soon after harvesting rather than fermented, helping to preserve naturally occurring plant compounds known as polyphenols.

Among the best-known of these compounds are catechins, particularly epigallocatechin gallate, or EGCG. Green tea also naturally contains caffeine. Together, catechins and caffeine have attracted considerable interest for their possible effects on energy expenditure, fat oxidation and body weight.

Green tea is frequently promoted as a weight-management ingredient, but the evidence does not support viewing it as a standalone weight-loss treatment. Some clinical studies have reported small reductions in body weight, BMI or waist circumference, while other trials and systematic reviews have found little or no meaningful effect. If green tea does contribute to weight loss, current evidence suggests that the effect is likely to be modest.

Key Facts

  • Green tea comes from the Camellia sinensis plant and contains polyphenols known as catechins.
  • EGCG is one of the principal catechins found in green tea and is commonly standardised in concentrated green tea supplements.
  • Green tea also naturally contains caffeine, although the amount varies between drinks and supplements.
  • Catechins and caffeine have been investigated for their possible effects on energy expenditure and fat oxidation.
  • Some meta-analyses have reported small reductions in body weight and BMI following green tea supplementation, but results differ considerably between studies.
  • A Cochrane review concluded that weight loss associated with green tea preparations was very small and unlikely to be clinically important.
  • More recent research continues to suggest that any effect on weight is likely to be small and the certainty of the evidence is limited.
  • Green tea should not be considered a substitute for a balanced diet, regular physical activity or clinically appropriate weight-management treatment.
  • Concentrated green tea extracts require more caution than ordinary brewed tea because high doses of catechins, particularly EGCG, have been associated with rare cases of liver injury.

Medino Recommends

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Lamberts Green Tea 5000mg 60 Tablets

Lamberts Green Tea provides a concentrated green tea extract equivalent to 5000mg of green tea leaf per tablet. Each tablet provides 250mg of total polyphenols and naturally contains approximately 25mg to 40mg of caffeine.

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Lindens Health + Nutrition Green Tea 1000mg 100 Tablets

Each Lindens Green Tea tablet contains 200mg of a 5:1 green tea extract, equivalent to 1000mg of dried green tea leaf. It provides 120mg of polyphenols, including 80mg of catechins. The tablets are suitable for vegetarians and vegans and provide a straightforward way of supplementing green tea extract without the need to prepare several cups of tea.

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NOW Foods Green Tea Extract 400mg 100 Veg Capsules

NOW Foods Green Tea Extract provides 400mg of green tea leaf extract per capsule, standardised to contain at least 40% catechins. Each capsule contains up to 32mg of naturally occurring caffeine and also provides 60mg of vitamin C.

FAQs

What does the research say about Green Tea and its effects on the body?

Much of the research into green tea has focused on its catechins, particularly EGCG, together with caffeine.

These compounds have been investigated for their potential effects on energy expenditure, fat oxidation, cardiovascular health and antioxidant activity. Laboratory studies provide several possible mechanisms through which catechins could affect metabolism, but demonstrating a mechanism is not the same as showing meaningful weight loss in people.

A 2010 meta-analysis of 15 randomised controlled trials found that green tea catechins combined with caffeine were associated with modest reductions in body weight, BMI and waist circumference. The average reduction in body weight compared with caffeine alone was around 1.4kg. However, the researchers described the clinical significance of these changes as modest at best.

A later Cochrane review examining green tea preparations in adults who were overweight or obese concluded that the average amount of weight lost was very small and was not likely to be clinically important.

A 2020 systematic review and meta-analysis reported an average reduction in body weight of around 1.8kg and a small reduction in BMI, although the studies varied considerably in their doses, formulations, duration and participant characteristics.

More recently, a 2024 network meta-analysis found that drinking green tea was associated with a small reduction in body weight compared with placebo or water. However, the evidence was rated as low or very low certainty and many of the included trials had a high risk of bias.

Taken together, these studies suggest that green tea may have a small effect on body weight in some circumstances, but it should not be expected to produce substantial or reliable weight loss.

Can Green Tea help with weight loss?

Possibly to a small degree, but it is important to keep the size and certainty of the effect in perspective.

Some controlled trials and meta-analyses have found modest reductions in body weight, BMI or waist circumference when green tea or concentrated green tea extracts were used for several weeks.

Other analyses have found little difference compared with placebo. The US National Institutes of Health Office of Dietary Supplements concludes that, if green tea does have an effect on weight loss, the effect is small and unlikely to be clinically significant.

Green tea should therefore be viewed, at most, as potential additional support within a wider weight-management programme. Maintaining an appropriate energy intake, eating a balanced diet, remaining physically active and developing sustainable habits are considerably more important.

Taking a green tea supplement does not guarantee that you will lose weight.

How might Green Tea support weight management?

Two components are usually discussed in relation to green tea and weight management: catechins and caffeine.

Caffeine can temporarily increase energy expenditure and stimulate the nervous system. Green tea catechins, particularly EGCG, have also been investigated for their possible influence on thermogenesis and fat oxidation.

Some researchers have suggested that catechins and caffeine could work together to produce a small increase in daily energy expenditure or the amount of fat used for energy.

However, an increase in fat oxidation during a laboratory measurement does not necessarily translate into meaningful long-term weight loss. Body weight is influenced by total energy intake and expenditure over time, alongside sleep, activity, health, medicines, genetics and many other factors.

The proposed metabolic effects of green tea therefore provide a possible explanation for the small changes seen in some studies, rather than evidence that green tea acts as a powerful 'fat burner'.

Does Green Tea boost metabolism?

Green tea may have a small, temporary effect on energy expenditure, particularly when it contains both catechins and caffeine.

Studies investigating this effect have produced variable results, and differences in caffeine intake, green tea formulation, dose and individual metabolism may all influence the response.

Even where an increase in energy expenditure is measured, the effect is generally modest. It should not be interpreted as meaning that green tea substantially increases metabolism or allows someone to lose weight without changes to their overall diet and lifestyle.

Does Green Tea burn belly fat?

There is not enough evidence to say that green tea specifically targets abdominal or visceral fat.

Some trials and meta-analyses have reported small reductions in waist circumference following green tea supplementation. However, waist circumference is an indirect measure and does not demonstrate that green tea selectively 'burns' fat from the stomach.

Where weight or body fat is lost, the body determines where that fat comes from. Supplements cannot reliably direct fat loss towards a particular area.

Is drinking Green Tea the same as taking Green Tea extract?

No. Brewed green tea contains catechins and caffeine in a relatively dilute drink, while supplements can provide much more concentrated extracts in a single tablet or capsule.

Many weight-management studies have investigated concentrated preparations rather than ordinary cups of green tea, so results cannot always be applied directly from one form to another.

There are also important safety differences. Green tea consumed conventionally as a drink is generally considered safe for adults, although it contains caffeine. Concentrated extracts have been associated with gastrointestinal side effects and rare cases of liver injury.

How much Green Tea should I take for weight loss?

There is no established dose of green tea or EGCG that has been proven to cause weight loss.

Clinical studies have used widely differing quantities of catechins, EGCG and caffeine, making it difficult to translate research doses into a general recommendation.

If you use a green tea supplement, follow the manufacturer's dosage instructions rather than increasing the amount in an attempt to accelerate weight loss.

It is also worth looking at how much caffeine and EGCG a product provides rather than comparing supplements solely according to the equivalent milligrams of dried green tea leaf.

Are there any known side effects or precautions when using Green Tea?

Green tea consumed as a normal drink is generally well tolerated by adults, although its caffeine content can cause effects such as restlessness, difficulty sleeping, headaches, palpitations or digestive symptoms in people who are sensitive to caffeine.

Concentrated green tea extracts require greater caution. Reported side effects include nausea, constipation and abdominal discomfort.

Rare cases of liver injury have also been associated primarily with concentrated green tea extracts. The European Food Safety Authority reviewed this issue and found evidence of increased liver enzymes in some people taking supplements providing 800mg of EGCG per day or more. EFSA was not able to establish a dose of supplemental EGCG that could be considered completely free from risk.

Taking concentrated extracts on an empty stomach may increase exposure to EGCG, which is one reason many products specifically advise taking them with food.

People with liver problems should seek professional advice before using concentrated green tea extracts.

Does Green Tea interact with medicines?

Green tea and green tea extracts can interact with some medicines.

Research has identified interactions with medicines including nadolol, a beta blocker, and atorvastatin. Other interactions are also possible.

Anyone regularly taking prescription medication should therefore check with a pharmacist, GP or other healthcare professional before starting a concentrated green tea supplement.

Can I take Green Tea supplements during pregnancy or breastfeeding?

Green tea naturally contains caffeine, and concentrated supplements may provide substantially different quantities of catechins and caffeine from an ordinary cup of tea.

People who are pregnant or breastfeeding should take account of their overall caffeine intake and seek advice from a healthcare professional before using concentrated green tea supplements.

Individual product instructions should also be followed. Some green tea supplements specifically state that they are not suitable during pregnancy or breastfeeding.

How long does Green Tea take to work for weight loss?

There is no established period after which green tea can be expected to produce weight loss.

Most clinical studies examining changes in body weight have lasted for several weeks or months, with many running for around 12 weeks.

This does not mean that taking green tea for 12 weeks will result in weight loss. Even in studies that have found an effect, average changes have usually been small, and some participants will experience no meaningful difference.

Progress with weight management is better assessed through sustainable changes in diet, activity and health behaviours rather than expecting a green tea supplement to produce a particular amount of weight loss within a set timeframe.

What should I look for when purchasing Green Tea supplements?

Look for a product that clearly states how much green tea extract is supplied per serving and, ideally, provides information about its catechin, polyphenol or EGCG content.

An equivalent dried-leaf figure can be useful, but it does not necessarily tell you how much of the active catechins a supplement provides. Two products both described as high-strength green tea may contain quite different amounts of EGCG.

It can also be useful to check:

  • The amount of caffeine per serving
  • Whether the extract is standardised for catechins or EGCG
  • Whether it should be taken with food
  • The recommended maximum daily serving
  • Warnings relating to pregnancy, breastfeeding or liver conditions
  • Whether the product contains other caffeine-containing or weight-management ingredients

More is not necessarily better with concentrated green tea extracts, so the recommended dose should not be exceeded.

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