Do Any Weight Loss Drugs Work?

A selection of weight loss pills and supplementsWeight loss pills are certainly becoming more popular, partly as the result of aggressive marketing online. The pharmaceutical industry is obviously very keen to create a weight loss pill for the mass market. The weight loss industry is very lucrative, and is still a growing industry as more people become obese. Estimates, based on current obesity trends, indicate that 50% of mean will be obese by the year 2050. A totally shocking prediction.

MotleyHealth’s Opinion on Weight Loss Drugs

Although we run through the various products that are currently on the market below, it is important that we make our stance clear from the start.

Weight loss drugs should not play any part in weight loss unless prescribed by a doctor. Over-the-counter (and those ordered online) will at best do nothing and at worse make you sick. While some of the drugs may aid weight loss, they will never result in more weight loss that diet and exercise.

We are not saying that weight loss pills are a waste of money simply because we endorse healthy eating and exercise as the best route to fitness. We endorse diet and exercise because it is the best, the easiest and the cheapest way to lose weight.

Health Warning

You should only consider weight loss pills if you have been prescribed them by your doctor. The only times they should be used is if you are unable to exercise due to severe obesity. All weight loss pills have known side-effects, and some may have yet undiscovered side-effects.

However, as some people will seek the pills anyway, we have decided to review what is currently available on the market. We certainly do not endorse their use. Always consult a medical professional before taking any medication.

What Are Weight Loss Pills?

Weight loss pills are generally designed to work by one of these processes:

  • By increasing metabolism – a common method that uses caffeine mostly
  • By aiding the breakdown of fat – another common method that uses some properties found in green teas
  • By suppressing appetite
  • By blocking the absorption of macronutrients – e.g. preventing fats or carbs to be taken into the body after digestion. Still experimental and can pose serious health risks

Important Note: Natural Herbs and Compounds – many pills are extracts and concentrations of various vegetables, fruits or other plants and have no scientific evidence of their effectiveness. e.g. Acai, African Mango, Raspberry Ketone (fruits), Green Tea (herbs) or Hoodia (plant). There are always vague studies, usually on rodents, that suggest a possible relationship between fat loss and the compound under certain circumstances, but never any evidence that they work on humans. Most of the early research is often found to have been false in follow-up trials. These are not strictly “drugs” or “medicine”. They are often not regulated by health bodies (such as the FDA) and rarely work. You can learn more about these on our Dangerous Diets page.

In short, the ones that boost metabolism only cause a small increase and strict diet is still required. The same is true for the pills that increase the breakdown of fats, as they exploit the findings in some studies into green teas for fat loss. In both cases the pills only make a small change to the amount of calories burned each day, certainly not enough to work in isolation.

Scientists are mostly working on producing a pill that block fats from being absorbed. This is potentially the best way to help people to lose weight, however, it also poses serious health risks.

Weight Loss Pills Alter Digestion

The three macronutrients that make up a human diet are carbohydrates, proteins and fats. Each of these is broken down (digested) by a different enzyme. For example, carbohydrates are broken down by amalyse enzymes to produce sugars, proteins are broken down by protease to produce peptides and fats are broken down by lipase to produce lipids. The body controls the production of these enzymes naturally, usually controlled by hormones.

So to reduce uptake of fat from the diet, weight loss pills will block the action of lipase, which means rather than fats being broken down and digested, they will be passed through the body and excreted.

This may sound like a good idea at first, but fats contain many essential nutrients and blocking all fat will lead to malnutrition and ill-health. So if you have heard news reports in recent years about weight loss pills that block fats, this is why they never make it to market – they are just too dangerous. People will abuse them, fail to follow the instructions and put their health at risk.

What Options Are On The Market?

The two main types of medicine that are on the market are a noradrenergic agent (which are essentially types of anti-depressant and should be administered by a psychiatrist) which acts as a short-term weight loss solution (defined as up to a 3 month treatment), and a lipase inhibitor (fat blocker) which is designed for long-term weight loss.


Phentermine suppresses appetite and makes you feel full quicker. Basically it is designed to block various neurological signals that makes us want to eat and also engages some hormones that make us want to stop eating. This drug used to be administered as phentermine-fenfluramine but led to increased blood pressure and heart problems so was withdrawn. Phentermine itself has a long list of side effects, some serious, such as irritability, nervousness, restlessness, insomnia, constipation, headaches, heart palpitations and high blood pressure. Branded as Adipex-P and Ionamin.


Another appetite suppressant that is taken before meals. Again, you should only take this after speaking with your doctor due to various possible side effects, conflicts with other medications and issues with dependency and addiction. Also many of the side effects seen in phentermine have been experienced. Branded as Tenuate.

Benzphetamine and Phendimetrazine

Two more drugs that manipulate the nervous system to control appetite and satiety. They both increase blood pressure and heart rate, so patients should be monitored by a doctor while taking this medication.


This is a lipase inhibitor (fat blocker). It binds to gastric and pancreatic lipases (enzymes that digest dietary fat), preventing these enzymes from hydrolyzing fat into absorbable free fatty acids. Basically, the fat passes through the gut without its energy being transfered into your body.

Various side effects are common, such as bloating, fecal urgency, fecal incontinence, and oily stools. Orlisat can block the uptake of vitamins A, D, E, and K so care must be taken to avoid malnutrition.

Orlistat is branded as Xenical (prescribed) and Alli (over the counter).


This drug is still in development (December 2010) and is similar to Orlistat. It is a fat blocker but with less common side effects.

Why The Drugs Often Fail

The problem with weight loss pills is that they simply do not tackle the root cause of the problem. People gain weight as a result of overeating. If you provide someone with a pill that blocks some fats and sugars, increases metabolism and suppresses appetite, they may well lose weight, but they will never learn how to manage their weight without pills.

Only by adapting to a better lifestyle, with an improved diet and becoming more active will people really be able to manage their weight in the long-term. Weight loss pills are not the solution – except in cases which require careful medical supervision, such as patients that have to lose weight quickly for surgery or other serious health reasons.

The pills that are marketed as metabolism boosters really do very little at all. Drinking more coffee may be as effective, cheaper and more pleasurable. The increased metabolic rate will never effectively burn enough calories to allow anyone to lose weight if they do not also change their diet. Exercising for 15 minutes in the morning probably has a better effect than any caffeine or green tea extract can.

So many people have managed to lose a significant amount of weight by following a simple calorie restrictive diet and exercise program that it does seem absurd that other people think that they can only lose weight by means of medication. Often some good old-fashioned advice and motivation will provide a better solution than pills.

More like this in the Weight Loss section

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