Weight loss - Medical information

  • Orlistat 120mg (Xenical) and orlistat 60mg (alli) capsules for weight loss in adults.
  • Orlistat 120mg capsules for use when BMI is over 30.
  • Orlistat 60mg capsules for use when BMI is over 28.

An overweight person has large amounts of fat stores and this fat is what contributes to their weight, body shape, and also many poor health effects. Orlistat reduces the absorption of fat and, as part of a lifestyle change, can help with weight reduction.

How to assess weight: overweight and obese

The words 'overweight' and 'obese' are medical terms, relating to the health risks from having too large fat stores. The World Health Organisation considers obesity to be a chronic disease.

We all have a general idea of what seems like a healthy weight, and what appears to be too much or too little. However, our mental picture is heavily influenced by the size and shape of the people we generally see around us, and so can often be unreliable. In fact three quarters of adults between age 45 and 74 in England are overweight or obese.

Body Mass Index (BMI) is a calculation combining weight and height, which gives a clearer indication of whether a person is in the healthy or overweight zones.

BMI and healthy weight

Weight BMI kg/m2
Underweight < 18.5
Healthy weight 18.5-25
Overweight 25-30
Obese 30-40
Severely obese > 40

Does being overweight or having obesity matter?

Yes! The bottom line is that people with obesity or overweight die younger from a variety of causes.

Many chronic conditions and cancers are directly linked to being overweight or obese. These include:

  • Coronary heart disease
  • Type 2 diabetes
  • High blood pressure
  • High cholesterol
  • Stroke
  • Dementia
  • Breast cancer
  • Bowel cancer
  • Non-alcoholic fatty liver disease
  • Respiratory problems and asthma
  • Gallbladder disease
  • Gastro-oesophageal reflux disease
  • Kidney disease
  • Osteoarthritis
  • Sleep apnoea
  • Depression and anxiety

Having obesity or being overweight can worsen general body aches and pains, and can have a marked effect on mobility, making daily life more difficult and leading to a lower quality of life.

It is recommended that anyone with a BMI over 30 should have a medical check up to assess and manage their personal health risks.

Studies show that people with obesity or overweight who lose at least 5-10 kg will significantly improve their general health.

How to lose weight

Our bodies are designed to store any excess food and calories as fat. This is obviously a good thing if food supplies are scarce. However in a developed society without major food famine, there is often a tendency to eat more than our bodies actually need and so more and more fat stores are laid down.

The simple answer to losing weight is to limit food and calorie intake to less than the body requires so that the body starts to use up the stored fat. But in reality it is often much more complex and difficult!

There is a huge industry promoting different programmes and diets to assist and encourage people in this. Some are scientifically developed, some involve low calorie replacement meal products, some can seem very extreme! Each person needs to find the method which works best for them, but losing weight will usually involve a commitment to a lifestyle change with new healthy eating patterns and more exercise!

Orlistat capsules have been medically proven to help with weight loss as part of those changes.

Weight loss is not easy and, sometimes it takes a long time and many tries, with weight going up as well as down, to find the best long-term diet and exercise solution for you. Remember - any weight lost and kept off will have permanent positive impacts on your health.

What is orlistat?

Orlistat is available as 60mg or 120mg strength hard capsules; as branded Xenical (120mg) or alli (60mg), and also as a generic medicine. The active ingredient is orlistat.

Orlistat inactivates the gut enzymes needed to absorb fat from food. When taking orlistat 120mg, about a third of the fat which is eaten passes straight on through the system and leaves the body in the stools. With orlistat 60mg, a quarter of the fat eaten will pass straight through. Orlistat reduces the calories being absorbed and contributes to weight loss.

  • We supplies Orlistat 120mg (Xenical) for people with a BMI over 30.
  • We supplies Orlistat 60mg (alli) for people with a BMI over 28.

Orlistat 120mg can also be used in some situations by people with a BMI between 28 and 30 if they have other risk factors for weight-related illness. Discuss with your regular doctor if you think you may benefit from Orlistat 120mg but your BMI is less than 30.

Orlistat will only help with weight loss alongside other changes including diet and exercise.

How to eat when taking orlistat

Orlistat is only effective if taken alongside a nutritionally-balanced, calorie-controlled diet. About a third of the calories should be from fat. Fat can often be 'hidden' within foods and it may be easier to use a fat calculator, initially, to work this out. The food, calorie, and fat intake should be spread evenly over 3 meals. Calorie and fat counters and diet apps may be helpful to set targets and monitor the diet.

A nutritionally balanced diet includes:

  • Five portions of fruit and vegetables per day.
  • High fibre, starchy foods.
  • Low fat milk and dairy.
  • Small to moderate portions of protein: meat, fish, eggs, beans, lentils.


  • Cut down/cut out high-fat foods, sugar, and salt.
  • Don't fry meals - grill or steam instead.
  • Cut down alcohol consumption (high in calories).
  • No snacks containing fat between meals - NO biscuits, cakes, savoury snacks, crisps.

This healthy balanced diet will lead to many health benefits as well as weight loss.

See also Diet plans for diabetics which are also really useful for non diabetics, prediabetics, and anyone wanting to lose weight.

How to take orlistat capsules

The capsules are usually taken 3 times a day, 1 capsule with breakfast, lunch, and dinner. The capsule can be taken just before the meal, with the meal, or up to an hour after the meal. The capsule should be swallowed whole with water. If a meal is missed, or the meal contains no fat, then the capsule should not be taken.

If a meal is known to contain very high amounts of fat then it is best to miss out the dose of orlistat, as there will be significant side effects.

Benefits of exercise on weight loss

Orlistat helps to reduce the amount of energy (calories) which is going into the system, but weight loss will be more effective when combined with an additional increase in the amount of energy being used. Most energy is used by the body when active, especially when exercising.

Exercise is seen by many as very daunting, with talk of gyms and running or swimming. In fact any moderate increase in activity will contribute not only to weight loss but to improvements in general health. The easiest exercise is the simplest - walk more.

Lots of studies have shown that 20-30 minutes of walking per day makes a big difference to health. You may need to double this in order to really assist in losing weight. As well as exercise, the World Health Organisation (WHO) also recommends limiting the amount of time spent sitting, especially in front of screens.

For exercise to help with weight loss, the key is increasing the amount of exercise from what has been normal for you. As with diet, it is important to introduce more exercise into your life in a way which you will be able to maintain.

Simple ways to increase walking include:

  • Getting off the bus a stop early.
  • Walking or cycling to the shops instead of using the car/bus.
  • Choosing a walk instead of watching TV, even if you feel tired!
  • Walking with a friend instead of meeting over a coffee.

Of course you can still choose a gym membership, a new active hobby, getting a dog, etc. - but be sure that these will actually lead to an ongoing increase in exercise.

Who should not take orlistat?

Orlistat should not be used in the following situations:

  • Allergy to orlistat or other capsule ingredients.
  • Malabsorption conditions - unable to fully absorb food from the gut.
  • Cholestasis - liver and bile duct disorder.
  • Pregnancy.
  • Breastfeeding.
  • Under 18 years old.

Orlistat 120mg (Xenical) and orlistat 60mg (alli) should not be used together.

Special care with orlistat

  • Kidney stones may develop if you already have kidney disease.
  • Thyroid hormone levels may drop.
  • Fat-soluble vitamin levels (vitamins A, D, E, & K and beta-carotene) may fall. If the diet does not contain adequate fruit and vegetables, a multivitamin supplement can be taken at bedtime.
  • After losing large amounts of weight, the dose of many medications may need adjusting. Consult your regular doctor after significant weight loss if you have diabetes, high blood pressure, high cholesterol, epilepsy, hypothyroidism.
  • Anyone who has suffered from Anorexia or Bulimia in the past.

Other medicines with orlistat

Blood levels of many other drugs may be affected. If taking any of the following, discuss with your regular doctor before starting orlistat:

  • Anticoagulant drugs especially warfarin.
  • Ciclosporin.
  • Levothyroxine.
  • Amiodarone.
  • Acarbose.
  • HIV medication.
  • Anti-epileptic medication.
  • Diabetic medication.
  • Antidepressants, antipsychotic medication, anti-anxiety medication.

Possible side effects of orlistat

Orlistat is not absorbed, and mostly remains in the gut so most of the side effects are related to the digestive system. As it prevents absorption of fat, the fat passes straight through the system and may lead to symptoms such as: abdominal discomfort, an urgent need to open the bowels, flatulence (wind) with discharge, oily discharge, oily or fatty stools, or fatty diarrhoea. These side effects often settle with time and with reducing dietary fat intake.

If there is actual bleeding from the bowel, consult your regular doctor.

Headaches and upper respiratory infections are also sometimes reported.

Further information in the manufacturer's patient information leaflet (links below).

Weight monitoring whilst taking orlistat

Orlistat 120mg (Xenical) should be stopped if you have not lost at least 5% of your starting weight after 3 months of treatment.

If weight loss is continuing, orlistat 120mg can be safely continued indefinitely, but clinical studies have not continued beyond 4 years.

If your BMI drops to between 28 and 30, We recommends swapping from orlistat 120mg to 0rlistat 60mg.

The manufacturers recommend that orlistat 60mg (alli) should be stopped after 3 months if there has been no weight loss, at all. Alli can be bought without a prescription. It is not recommended to be used for longer than 6 months in total. As with orlistat 120mg (Xenical), orlistat 60mg (alli) can actually be safely used indefinitely, but use of alli beyond 6 months is 'off label' and doctors take responsibility for the prescribing. We does not prescribe alli, if your BMI is below 28.