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Does tea help weight loss? What green tea and oolong studies show
Not by much. A Cochrane review found green tea made almost no difference to weight outside Japan, and the small boost in calories burned seen in lab studies comes mostly from caffeine. Tea can still help in one plain way: an unsweetened cup can replace a sugary drink. Steady eating, movement and sleep do the real work.
Written by the Cardio Slim Tea reading deskUpdated · 8 min read
The idea
Why do people think tea helps with weight?
Tea leaves contain catechins and caffeine. In lab studies, both nudge up the number of calories the body uses at rest, so the idea of a slimming tea took hold.
Ads then stretched that idea. A small rise in energy use became "melting" weight in some marketing. The real question is simple: in people who drink tea for weeks or months, does weight go down more than in people who do not?
The best way to answer is to look at controlled trials, where one group drinks tea and a similar group does not. Let's take green tea first, since it has the most research.
Green tea
Does green tea help you lose weight?
Barely, if at all. A Cochrane review looked at 15 weight-loss and 3 weight-maintenance studies with 1,945 people (Cochrane - Green tea and weight loss).
Outside Japan, six studies with 532 people found a difference of just 0.04 kg. That is less than one-tenth of a pound, and it was not statistically significant. Studies in Japan reported larger changes, from 0.2 to 3.5 kg, but they could not be pooled together (Cochrane - Green tea and weight loss).
The review authors judged the loss too small to matter for health. Green tea also did not help people keep weight off (Cochrane - Green tea and weight loss). The NIH Office of Dietary Supplements puts it this way: drinking green tea is safe and might help with a small amount of loss (NIH ODS - Weight-loss supplements).
Green tea extract pills are a different product. They have been linked to liver injury and can raise blood pressure (NIH ODS - Weight-loss supplements). A cup of brewed tea is not the same thing.
Oolong
What about oolong tea?
The oolong evidence is thinner still. One 6-week study gave 102 overweight or obese adults 8 g of oolong a day. About two-thirds lost more than 1 kg (He 2009 - Oolong tea and weight).
That sounds promising until you look at the design. The study had no control group. Without one, there is no way to know how many people would have lost a kilogram anyway, just from being in a study and paying attention to their habits (He 2009 - Oolong tea and weight).
Note the dose, too: 8 g of oolong a day. That is about four times the roughly 2 g of tea a day in a Cardio Slim Tea pouch, by our math, and that 2 g is shared by 14 named herbs.
Caffeine
Is it the tea or the caffeine?
Mostly the caffeine. A meta-analysis found that mixes of tea catechins and caffeine raised 24-hour energy use by about 4.7%, roughly 100 calories. Caffeine alone did almost exactly the same, about 4.8% (Hursel 2011 - Tea catechins and energy use).
A hundred calories a day sounds useful. But it was measured over a day in a lab, not as weight lost over months. The body also adapts to regular caffeine.
| Drink | Caffeine |
|---|---|
| Green tea | About 37 mg (FDA - Caffeine: how much is too much) |
| Black tea | About 71 mg (FDA - Caffeine: how much is too much) |
| Oolong | Varies; no verified figure in our sources |
| Cardio Slim Tea | Not published |
| Daily limit for most healthy adults | 400 mg (FDA - Caffeine: how much is too much) |
The seller lists Cardio Slim Tea's green tea as decaffeinated. Decaf green tea would add little of the caffeine effect. Oolong in the blend still carries some natural caffeine, though the amount is not stated.
Cardio Slim Tea: from $49 a pouch60 g herbal tea · 2, 3 or 6 pouches · 60-day money-back guarantee
See packsAt a glance
How strong is the evidence for each tea?
Large review, tiny effect
1,945 people; about 0.04 kg outside Japan, not clinically important (Cochrane - Green tea and weight loss).
One uncontrolled study
102 people, 8 g a day for six weeks; no comparison group (He 2009 - Oolong tea and weight).
Small lab effect
About 100 extra calories a day used, almost all from the caffeine (Hursel 2011 - Tea catechins and energy use).
For more on these two leaves, see the green tea and oolong page.
What works
What actually helps with weight loss?
Slow, steady habits. The CDC says losing about 1 to 2 pounds a week makes it more likely the weight stays off. Even a 5% loss can improve blood pressure, cholesterol and blood sugar (CDC - Losing weight).
Build meals around plants
Vegetables, fruit, beans and whole grains fill you up for fewer calories.
Move a little most days
A walk after meals is a fine start. Add a few minutes each week.
Swap sugary drinks
An unsweetened tea, hot or iced, can replace soda or sweet coffee. That is where tea earns its place.
Protect your sleep
Short nights make hunger harder to manage.
The NIH says there is little scientific evidence that weight-loss supplements work, and some interact with medicines (NIH ODS - Weight-loss supplements). Our healthy weight loss guide goes step by step.
The pouch
What does this mean for Cardio Slim Tea?
The pouch says "Helps In Natural Weight Loss*", with the FDA asterisk. No study has tested Cardio Slim Tea itself, and its ingredient amounts are not published.
The sales page tells of a group losing an average of 31 pounds. It names no study, control group or sample size (Cardio Slim Tea sales page). The FTC says customer stories are never proof that a health product works (FTC - Health Products Compliance Guidance). See how to read weight-loss tea ads.
If you enjoy the tea as an unsweetened drink, it can fit a weight plan. Credit the swap and the habits, not the herbs.
Keep taking every prescribed medicine. Never stop or change one because of a tea; ask your healthcare professional first (AHA - Types of BP medications).
FAQ
Tea and weight loss: FAQ
Does green tea help you lose belly fat?
There is no good evidence that it targets belly fat. A Cochrane review found green tea made almost no difference to overall weight outside Japan (Cochrane - Green tea and weight loss), and no food or drink can remove fat from one spot. Overall habits change waist size over time.
How many cups of green tea a day for weight loss?
No amount has been shown to cause meaningful weight loss. Trials varied, and the overall effect was tiny (Cochrane - Green tea and weight loss). If you enjoy it, a few unsweetened cups fit within the FDA's 400 mg daily caffeine guide for most adults (FDA - Caffeine: how much is too much).
Is oolong tea better than green tea for weight loss?
That has not been shown. The main oolong study had 102 people, used 8 g a day for six weeks and had no control group (He 2009 - Oolong tea and weight), so it cannot prove oolong caused any loss. Green tea has more research, and it also shows little effect.
Does caffeine help you burn more calories?
A little, for a short time. Caffeine raised 24-hour energy use by about 4.8% in lab studies, roughly the same as tea catechins with caffeine (Hursel 2011 - Tea catechins and energy use). That has not translated into meaningful weight loss in longer trials.
Do slimming teas work?
There is little evidence they do. The NIH says weight-loss supplements in general have weak support and some interact with medicines (NIH ODS - Weight-loss supplements). Some slimming teas also contain laxative herbs, which shift water, not fat. Read every label before you drink.
Is green tea extract safe for weight loss?
Green tea extract is riskier than brewed tea. It has been linked to liver injury (LiverTox - Green Tea) and can raise blood pressure (NIH ODS - Weight-loss supplements). Talk to your doctor before taking it, especially if you have liver disease, heart disease or high blood pressure.
Will drinking tea before bed help weight loss?
Not in any proven way, and caffeinated tea at night can disturb sleep. Poor sleep makes hunger harder to manage. If you want a warm drink in the evening, choose one without caffeine and skip added sugar.
Who wrote this
Written and reviewed by
Pages built from the pouch, the brand graphic, the sales page and linked NIH, FDA, FTC and peer-reviewed sources.
Last updated . Read our editorial standards and how we check reviews. This website is run by an authorized U.S. retailer, not by the manufacturer. We earn money when you buy through our order links.
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