When it comes to weight loss products, one of the most commonly posed questions certainly is how they actually work. And this question goes beyond just curiosity – the way slimming pills act in the organism in order to help the user lose weight makes the difference between healthy and unhealthy options, it is what makes certain products safe and legal and other dangerous, unregulated and illegal.

However, as is implied, there is no single answer to this. On the contrary, how weight loss pills work will depend on the nature of the specific weight loss tablet you are using. On the other hand, we can roughly group the available and regulated medications into several groups that share more or less similar mechanisms of action, albeit with slight differences.

What’s on this page?

So, for example, we have weight loss supplements which are available over-the-counter and which act significantly different as compared to typical prescription-only weight loss pills. Some of this might reduce the appetite of the user (or claim to do so), others might increase the rate at which the body spends energy and burns calories.

Weight loss medicines based on orlistat as an active ingredient are the only kind of prescription medications for losing weight in the UK. They include branded medications such as Xenical, generic Orlistat and Alli which is not a prescription medication in the narrower sense of the word, but which still requires the user to get an assessment by a doctor or pharmacist prior to use. These medications act very differently from supplements and appetite suppressants.

How does Orlistat work?

While the majority of medications, regardless of their specific intention, are uptaken into the bloodstream after which they become effective, orlistat-based drugs act in a different way – locally, directly in the gut.

Medically classified as a lipase inhibitor, Orlistat works by inhibiting the activity of specialised enzymes produced by the pancreas and gastrointestinal tract, called lipases. Without inhibitory activity of Orlistat, these enzymes help the body to extract fat from the food consumed, absorbing it into the blood before either converting it into energy or storing it. Orlistat interferes with this process by inhibiting lipase function and thus preventing fats from being absorbed, causing them to instead be excreted through faeces.

In order to be effective, orlistat-based medications should be taken just before or very shortly after consuming a meal. As such, they act specifically to prevent the fat from being absorbed from the most recent meal. So, if you plan to have a fat-free meal, you do not have to take the medication.

While Orlistat can’t completely prevent fat uptake, it still makes a significant difference by stopping at least 30% of the fats consumed from being absorbed. The studies have confirmed that this is enough to drastically reduce the intake of fats and calories, especially in people with a BMI of 27 or more. One such study showed that orlistat-based medicines can help users lose as much as one kilo per month.

Non-prescription weight loss medications

As of 2015, orlistat-based medications such as Xenical and Alli are the only weight loss prescription medicines available on the UK market. However, while Orlistat certainly holds its monopoly when it comes to weight loss medicines, there are several other non-prescription supplements and aids which can be legally obtained in the UK from high street pharmacies.

Because of this, you should be very careful when buying weight loss medication, especially when it’s online. If your supplier claims to have access to prescription medications other than Xenical, Orlistat or Alli, it is most likely an unsafe treatment which you should avoid. These medications are completely unregulated, meaning that they are not subject to strict regulations regarding manufacturing standards and clinical testing, making it impossible to correctly assess their safety or know with certainty how they work in the body.