Effectiveness: One study showed that it caused 9.5 kg of weight loss over a 3 month period.
Side effects: If you are caffeine sensitive, you may experience anxiety, jitteriness, tremors, nausea, diarrhea and irritability.
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Bottom Line:Unfortunately, there is only one study on this supplement and no data on long-term effectiveness. More research is needed.
2. Green Coffee Bean Extract
They contain two substances believed to help with weight loss, caffeine and chlorogenic acid.
How it works: Caffeine can increase fat burning, and chlorogenic acid can slow the breakdown of carbohydrates in the gut.
Effectiveness: Several human studies have shown that green coffee bean extract can help people lose weight.
A review of 3 studies found that the supplement made people lose 2.5 kg than placebo, a dummy pill.
Other benefits: Green coffee bean extract may help lower blood sugar levels, and reduce blood pressure. It is also high in antioxidants
Side effects: It can cause the same side effects as caffeine. The chlorogenic acid in it may also cause diarrhea, and some people may be allergic to green coffee beans
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Bottom Line:Green coffee bean extract may cause modest weight loss, but keep in mind that many of the studies were industry sponsored.
3. Garcinia Cambogia Extract
It is a small, green fruit, shaped like a pumpkin.
The skin of the fruit contains hydroxycitric acid (HCA). This is the active ingredient in garcinia cambogia extract, which is marketed as a diet pill.
How it works: Animal studies show that it can inhibit a fat-producing enzyme in the body and increase levels of serotonin, potentially helping to reduce cravings
Effectiveness: One study with 130 people compared garcinia against a dummy pill. There was no difference in weight or body fat percentage between groups
A 2011 review that looked at 12 studies on garcinia cambogia found that, on average, it caused weight loss of about 2 pounds (0.88 kg) over several weeks
Side effects: There are no reports of serious side effects, but some reports of mild digestive problems.
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Bottom Line:Even though garcinia cambogia may cause modest weight loss, the effects are so small that they probably won’t even be noticeable.
4. Caffeine
Caffeine is the most commonly consumed psychoactive substance in the world (6Trusted Source).
It is found naturally in coffee, green tea and dark chocolate, and added to many processed foods and beverages.
Caffeine is a well known metabolism booster, and is often added to commercial weight loss supplements.
How it works: Short-term studies have shown that caffeine can boost metabolism by 3-11%, and increase fat burning by up to 29%
Effectiveness: There are also some studies showing that caffeine can cause modest weight loss in humans
Side effects: In some people, high amounts of caffeine can cause anxiety, insomnia, jitteriness, irritability, nausea, diarrhea and other symptoms. Caffeine is also addictive and can reduce the quality of your sleep.
There really is no need to take a supplement or a pill with caffeine in it. The best sources are quality coffee and green tea, which also have antioxidants and other health benefits.
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Bottom Line:Caffeine can boost metabolism and enhance fat burning in the short term. However, a tolerance to the effects may develop quickly.
5. Green Tea Extract
Green tea extract is a popular ingredient in many weight loss supplements.
This is because numerous studies have shown the main antioxidant in it, EGCG, to aid fat burning.
How it works: Green tea extract is believed to increase the activity of norepinephrine, a hormone that helps you burn fat
Effectiveness: Many human studies have shown that green tea extract can increase fat burning and cause fat loss, especially in the belly area.
Side effects: Green tea extract is generally well tolerated. It does contain some caffeine, and may cause symptoms in people who are caffeine sensitive.
Additionally, all of the health benefits of drinking green tea should apply to green tea extract as well.
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Bottom Line:Green tea and green tea extract can increase fat burning slightly, and may help you lose belly fat.
6. Conjugated Linoleic Acid (CLA)
Conjugated linoleic acid, or CLA, has been a popular fat loss supplement for years.
It is one of the “healthier” trans fats, and is found naturally in some fatty animal foods like cheese and butter.
How it works: CLA may reduce appetite, boost metabolism and stimulate the breakdown of body fat
Effectiveness: In a major review of 18 different studies, CLA caused weight loss of about 0.2 pounds (0.1 kg) per week, for up to 6 months .
According to another review study from 2012, CLA can make you lose about 3 lbs (1.3 kg) of weight, compared to a dummy pill.
Side effects: CLA can cause various digestive side effects, and may have harmful effects over the long term, potentially contributing to fatty liver, insulin resistance and increased inflammation.
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Bottom Line:CLA is an effective weight loss supplement, but it may have harmful effects over the long term. The small amount of weight loss is not worth the risk.