How Do Diet Pills Work?

At the moment my life seems to have turned into a horribly gender clichéd romcom, in which I need to lose weight to get into an oh-so-special dress for a wedding. Imagine if you will, the voice-over guy introducing the trailer to my life, ‘Liz Granger is too tight-fisted to buy a new dress, but Liz Granger is about to find out sometimes losing weight to fit into an old dress isn’t as easy as it seems. Can Liz do it? Maybe with a possible love interest, some good friends, a little motivation and an exercise montage…she just might.’ I’m lining up Jen for the role.

Turns out the obstacle in this film would be the fact I like crisps, drink too much wine and avoid exercise.  So what’s a girl (or boy) to do?  There must be a quick fix answer, surely. Well, my fascination with everything that allows you to procrastinate on the internet has led me to some rather shady websites that peddle weight loss pills that promise you can lose a stone in two weeks. With this in mind I decided to look into the ‘science’ of how diet pills work – after all if they look like a real medicine they must work like a real medicine. Maybe I’m just thinking of the placebo effect there. Anyway these are some types of pills I found that you can pop à la the internet:


Yes, apparently if you want to lose weight you need to poop and you need to poop a lot. I can’t quite fathom this one, but I guess the logic is that if the food passes through you quickly enough it doesn’t get absorbed in your intestines. I can’t help but think it would be more pleasant to just eat healthily and not have diarrhoea, but I’m old-fashioned like that. A lot of the herbal diet pills you can buy are actually just weak laxatives and diuretics (diuretics make you pee more). Maybe if it’s natural it’s not as gross.


Most diet pills have caffeine in; there is evidence to suggest caffeine suppresses appetite and it certainly peps you up. I’m not convinced though, I drink a lot of coffee and I don’t think it’s making me any thinner. But then again, maybe if I didn’t drink coffee I’d be the size of a blimp. I’m guessing the caffeine just makes you feel like the pills having some kind of instant positive effect on your energy levels.

Fat Burners and Appetite Suppressants

This is a weird one. Lots of the active ingredients found in diet pills have some evidence to suggest they suppress appetite but they are also often marketed as ‘fat burners’ that speed up the metabolism.  Other fat burners have vague ingredients like ‘açaí berry extract’. Maybe they do burn fat, it’s difficult to say, but with most evidence (when there is evidence) being anecdotal rather than from a controlled trial, I’d be sceptical.

Incidentally, açaí berries are the fruit world’s answer to beefcake the powdered form is a third fat, and 100g of the powdered berries gives you 530 calories – twice as many calories as the same amount of French fries from McDonald’s. The main selling point of açaí berry extract is that it’s supposed to speed up metabolism because it is full of antioxidants. One of the most potent antioxidants that exist is vitamin C, so if consuming antioxidants makes you lose weight, you’d be better off buying a 90p packet of vitamin C tablets. But truth be told, you’d pee most of the vitamin C out and this is almost certainly what would happen with the vitamins in powdered açaí berry. So if I took them I’d pee out most of the goodness but I would still absorb the calories – brilliant.

 A compound called Phentermine is found in a lot of diet pills. It affects the fight or flight chemical messenger in the brain called noradrenaline (norepinephrine for Americans) and this is thought to suppress hunger. Its actions in the brain are actually pretty similar to those of a family of drugs that include amphetamine. You remember amphetamine, that illegal drug of abuse that is heavily addictive? Although Phentermine is considered a little safer than amphetamine it is still associated with high blood pressure and can affect the heart rate. During most of the 1990s a lot of diet pills contained Phentermine paired up with another compound called Fenfluramine – together they combined forces to make Fen Phen.  After around 10 years on the market Fen was linked to heart disease and was banned. I don’t know about you but that makes me a bit more cautious of diet pills in general.

A popular pill ingredient is p57 derived from a plant called Hoodia. Although there is evidence to suggest it can affect signalling in the brain and suppress the appetite of rats, the rats in question were injected with the molecule directly into their brain. So unless you’re going to inject your brain with p57, (to be clear no one should EVER do that), I’d take that with a pinch of salt.

Another potential appetite suppressant is an ingredient called 5HTP. Your body can convert 5HTP into serotonin, an important chemical messenger in the brain that controls mood and appetite. The problem is that taking in a lot of 5HTP doesn’t necessarily mean it will be made into serotonin. The body has some awesomely complex and amazing mechanisms for keeping all the hormones inside you balanced at the right level. Even if the building blocks for serotonin are available, it doesn’t mean it will be made into it so there’s a good chance you’ll just excrete it (hopefully without the aid of a laxative).

Fat binders

Regular laxative-induced diarrhoea not sexy enough for you? Why not try uncontrollable oil seepage. That’s right, seepage. Fat binders, unsurprisingly, bind to fat and stop it being absorbed. And when it’s not absorbed guess where it goes? These pills tend to make people avoid fatty food for obvious reasons, which also helps with weight loss. It’s pretty crazy we live in a society where people have to be scared of oil seepage to stop eating fatty food. Now where did I put those crisps….

My Options

So, here are my options: something that makes me go to the loo a lot, something that makes me poop fat, a questionable concoction herbal and non-herbal compounds that may or may not work but cost quite a lot of money and finally, lots of caffeine. It’s almost like eating sensibly and exercising might be an easier option.

It’s OK though, the conclusion to my movie is that I gave up and bought a dress that fits me. Don’t get me wrong I’m pretty happy with my size – there’s way too much pressure for women (and men) to be slim for superficial reasons. But thinking about all this did make me want to get healthier because basically I don’t want to get cancer, diabetes, heart disease or any of the other many weight- related diseases.  With this in mind I am going to start exercising more, try to kick the crisps habit and cut down on the wine. I definitely won’t be taking any diet pills, because even if they do work there is no way it is healthy to lose a stone in two weeks, no matter how much you don’t want to shell out for a new dress.

Post by Liz Granger

Twitter: @Bio_Fluff

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