Dieting is big business. There’s no shortage of diet pills and supplements on the shelves promising weight loss, advocating a quick and easy pill-popping method so that you can shed kilos fast. But how effective are they, really, in delivering the true extent of their weight loss claims?
UK celebrity doctor, Dr Xand van Tulleken, seeks to test whether diet pills actually work in episode one of the new series, The Diet Testers, staring on SBS on Thursday 1 March at 8.35pm.
He hones in on three popular kinds of diet pills available in the UK and Australia – raspberry ketones, carb blockers and fat burners.
Here are the results of three experiments which feature in the show.
Raspberry ketone is the chemical compound gives berries their signature scent. Source: Sergey Kukota via Flickr
Tested: The Raspberry ketone diet pill
The raspberry ketone diet pill, made famous by Kim Kardashian’s usage, claims to help the body burn fat faster than usual. It is believed to achieve this by causing the fat within cells to break down more effectively and increasing your metabolism.
Purely for the sake of research, Dr Xand van Tulleken tests the pill by taking two doses a day as instructed for two days.
According to the label of the particular brand he samples, the raspberry ketone diet pill should have suppressed his appetite and cravings, and provided him with the willpower needed to diet.
So how’d he go? Did he feel less hungry or more energised?
All the evidence is from feeding raspberry ketones to rats and mice.
“The raspberry ketones I tested didn’t have any effect on me whatsoever, granted I only did two days and tried only one brand,” says Dr Tulleken on the show.
Professor of Metabolic Medicine at, believes that the marketing claims made by most raspberry ketone pills are not backed by appropriate evidence.
“I don’t think we know [if it helps us to lose weight] because experiments on humans conducted in a proper way have not been done,” says Prof Karpe, who appears in the show. “All the evidence is from feeding raspberry ketones to rats and mice.”
Dr Tullekan agrees: without wide-spread research conducted on humans, there’s no actual proof that raspberry ketone diet pills are overly effective in helping populations to lose weight.
“As far as we are aware, raspberry ketones have not been tried for weight loss in humans so there is not a shred of evidence that they will help people to lose weight.”
Tested: Carb blockers
The next diet pill on the show’s road-test circuit is a carb blocker. The diet supplement, also known as a , aims to help block the enzymes required for your body to digest specific carbohydrates.
Essentially, that means by taking a carb blocker pill, you’re still able to eat carbs but your body won’t digest it. So if the marketing promises ring true and this drug does what it claims, then you get to have your bread and eat it too – your body won’t absorb all the carbs in your blood or retain the associated calories.
There are many types of carb blockers available on the market. In episode one of The Diet Testers, Dr Tulleken teams up with the Oxford University scientist, Professor Karpe, on the show to examine this kind of diet pill more thoroughly.
If this [the pill] is effective then there will be a substantial portion of breakfast that won’t be absorbed. Then they are likely to end up with wind.
They conduct randomised double-blind placebo controlled trial for the show. They gave a small group of volunteers blood tests, then split the group up into two smaller groups: some who were given a placebo and others who were given a carb blocker.
The entire group then consumed a high carbohydrate breakfast of cereal and yoghurt. They then did a blood test each hour for four hours to find out whether the carbohydrates were absorbed into the blood stream.
“If this [the pill] is effective then there will be a substantial portion of breakfast that won’t be absorbed,” Prof Karpe says. “Then they are likely to end up with wind.”
Maybe it was because the cameras were on but on participant reported such obvious effects. In fact, according to Prof Karpe, “the people who took the carb blocker had exactly the same blood glucose levels as those with the placebo”.
“There is no difference between the groups here,” he says. “It did nothing.”
The study conducted for the show was only small and conducted over a limited period of time. Only one carb blocker was tested.
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Tested: Fat burner diet pills
Fat burners claim to help you to burn fat faster. There’s a number of different ways they can do this: increase your metabolism, curb your appetite and promote fat to be used for energy.
Prof Karpe and his team conducted the same experiment as the carb blocker test for the show, but this time around they used a fat burning diet product that aims to induce ketosis by raising the level of ketone bodies in the tissues.
Hence, blood tests were conducted as part of the experiment to examine the presence of ketone bodies and show if the body was actually burning fat.
This is just what we would expect from having an extra cup of coffee or something like that.
“The people who took the fat burner pill ended up with just slightly higher ketone bodies [in their blood],” says Prof Karpe. “So it worked to some little extent.”
But no, says Prof Karpe, it won’t help you to lose weight. “This is just what we would expect from having an extra cup of coffee or something like that.” So perhaps it’s best for you to spend your money on an extra cuppa instead.
The team concluded that fat burner diet pills wouldn’t do you any harm if you take them in the recommended dose but they are unlikely to help you achieve your weight loss goals.
Want to know whether there's any truth behind some of the world's most popular dieting methods? Watch the new season premiere of 'The Diet Testers', airing on SBS from Thursday 1 March at 8.35pm. Episodes will be available to watch after broadcast on
