Orlistat
A Medicine To Help With Weight Loss

How can I lose weight?

To lose weight, the best chance of long term success is to eat a healthy diet and, if you are able, to exercise regularly. See separate leaflet called 'Weight Reduction - How to Lose Weight' for details. There is only a limited role for medicines to help with weight loss.

Orlistat is a medicine that is sometimes advised. However, it is no 'wonder-drug', it only partially helps, and you still need to eat less to lose weight.

How does orlistat work?

Orlistat works by blocking chemicals (enzymes) in your gut which digest fat. Nearly a third of the fat that you eat is blocked by orlistat. The undigested fat is not absorbed into your body, and is passed out with your faeces (stools). The normal dose is one capsule, three times a day with each meal. However, you do not need to take one if there is no fat in the meal.

How effective is orlistat?

Studies have shown that, on average, orlistat plus a weight-reducing diet and exercise causes more weight loss than a weight-reducing diet and exercise alone. Some people lose 10% or more of their body weight within six months with the help of orlistat. In others, it is less effective.

One reason why orlistat may not work is that you may think that you can relax your weight-reducing diet, and the orlistat will 'do it all'. This is not true. You still have to eat less. Remember, orlistat prevents only some of the fat that you eat from being absorbed (just under a third). But, if you do not keep to a healthy weight-reducing diet, and eat more fat (chocolates, cakes, etc), the extra fat that you eat will easily cancel out the effect of the orlistat.

Guidelines for using orlistat

Doctors are expected to follow guidelines when prescribing orlistat. These include:

• your BMI (Body Mass Index - see below)
  • must be 30 or above, or
  • must be 28 or above, and you have a medical condition that would benefit from losing weight (such as diabetes or high blood pressure).
• you must lose at least 5% of your weight by three months from starting orlistat, and at least 10% of your weight by six months. If not, the orlistat should be stopped.
• you must be between the ages of 18 and 75 years.

Are there any side effects with orlistat?

The main side effects are caused by the fat which is passed out with your faeces. You may get fatty smelly stools, urgency to get to the toilet, oily spotting on your underclothes, and excess wind. These side effects are less likely if you eat a low-fat diet. They tend to settle with time, possibly because if they occur they remind you that you should be eating a low-fat diet! Other side effects are rare. (Read the packet leaflet for a full list of possible side effects.)

Pregnant women, breastfeeding women, and children should not take orlistat.

What is my body mass index (BMI)?

BMI, mentioned above, is a good estimate of how much of your body is made up of fat. It relates your weight to your height. You can work out your BMI by dividing your weight (in kilograms) by the square of your height (in metres). So, for example, if you weigh 70 kg and are 1.75 metres tall, your BMI is 70 / 1.75 x 1.75, which is 22.9. Alternatively, your practice nurse can measure and weigh you, and tell you your BMI.

Keeping to a reduced weight

A number of people who lose weight with the help of orlistat put the weight back on once the orlistat is stopped. Try to anticipate this.

Once you have lost some weight, you are more likely to keep your weight down if you stick to a healthy diet, exercise regularly (if you are able), and weigh yourself once a week.

Further help

See your practice nurse for further help and advice about a healthy diet and exercise. There are also more detailed leaflets in this series called 'Weight Reduction - How to Lose Weight', 'Healthy Eating', and 'Obesity and Overweight'.

© EMIS and PIP 2005   Updated: September 2005   PRODIGY Validated