What is the evidence behind weight loss pills?

Dr Nick Fuller
Leading Obesity Expert at the University of Sydney and founder of Interval Weight Loss.

New data has just been released showing that nearly half of us are now taking vitamins and supplements – everything from multivitamins, to supplements for digestive health, and formulas for healthy joints. 

This is now a billion dollar market with no sign of it slowing down. And with two in three people now struggling with their weight, weight loss supplements make up, what is, one of the largest growing markets in the world! Sadly, this comes as no surprise, with many turning to these pills in a desperate attempt to shift the kilos. 

The list of dietary and weight loss supplements is exhaustive. It’s a perplexing field to navigate with the most popular weight loss supplements containing more than one specific ingredient – often including a concoction of ingredients such as vitamins, minerals and herbs.

But do any of the weight-loss supplements actually work?

Here are four common ingredients we now see in weight loss supplements:

1. Green coffee extract

There are many weight loss supplements that contain an extract from coffee - green coffee extract - as their main ingredient. Green coffee extract is rich in chlorogenic acid which is purported as the active ingredient for weight loss. One such example is ‘Hydroxycut’. Despite several safety recalls of this product over the past decade, this company has succeeded with master craft marketing ever since its development. Earlier formulations contained ephedra, a stimulant that causes heart problems and stroke, and consequently it was banned in 2004. But clever entrepreneurial activity saw revised formulas back on the market. Serious safety concerns meant it was banned again, and the product we see on the shelves today is again a different formulation, containing green coffee extract.

There is no scientific evidence to suggest green coffee extract assists with weight loss. And there is no research that specifically looks at the Hydroxycut product range to show that it works. In fact, all of the research they cite on their website has either been withdrawn due to serious scientific flaws; is unpublished - meaning it was never reviewed outside of the company; or has been translated from other languages, with serious question around the science.

2. Hemp seeds

Yes, it is what you think it is. Hemp seeds are the seeds of a variety of Cannabis plant, which is where marijuana comes from. Can you believe that this is the latest buzz and promise to solve all our weight problems? Sorry to be the bearer of bad new but there is no research to suggest that hemp can help with weight loss and this is just clever marketing. In fact, many of the sites that claim it helps with weight loss simply reference other sources that are just making the same bold statements as themselves without any proof. Clever isn’t it!

We can get all of the nutrition that companies selling hemp are basing their marketing on - for example, a source of good fats and high in protein - from plenty of wholesome nutritious foods that don’t contain tetrahydrocannabinoids (THC). Even though these levels are considered very low when compared to marijuana, it won’t help with weight loss, and certainly not worth any potential health risk that can be associated with ingestion of THC.

3. Garcinia 

Garcinia cambogia is a plant that produces a fruit. The skin of the fruit contains the active ingredient, hydroxycitric acid (HCA) which is its purported active ingredient for blocking the formation of fat and weight loss. Most of the science investigating whether Garcinia Cambogia actually works has been conducted in animals. And for those well conducted studies that have been conducted in humans it’s proven to be no better than a placebo or dummy pill, or in the best case provide very small amounts of weight loss – 1 kg - that is not clinically meaningful.  

There are many products that contain garcinia as one of their listed ingredients. ‘Fat Blaster’ is one example with its revised formula containing garcinia, green tea, green coffee extract and guarana. But again there is no evidence supporting the bold weight loss claims it makes.

4. Capsaicin 

Capsaicinoids are the active components in chilli peppers which give them their heat. Some research suggests it increases the amount of energy we burn after a meal but the science on its weight loss potency is lacking. 

No studies have tested capsaicin as a stand-alone ingredient for weight loss but instead have only tested multi-ingredient supplements which contain other herbs and stimulants such as caffeine, guarana, raspberry ketones, garlic and ginger. All of these ingredients lack the science to justify their cost.

Take home messages:

1. Some vitamins and supplements do have evidence supporting their claims for different health conditions, but with respect to the ingredients and weight loss pills reviewed here, this is certainly not the case.

2. Any products with the words ‘shred’, ‘blaster’ or ‘skinny’ aren’t going to do what they promise and it’s simply a clever marketing scheme. Avoid them at all cost.

3. Ensure to review the science when it comes to choosing a weight loss supplement. Don’t believe the bold statements that a company makes on its website. Investigate yourself!

4. Avoid supplements that contain a mixture of ingredients as they are less likely to be safe for consumption and may cause serious health problems.

5.  The same product can vary enormously between manufacturers so make sure to buy the specific supplement and brand with proven research supporting its claims.