Orlistat: Blocking Fat To Lose Weight

The alarming rate at which obesity and weight gain is growing, the scientists are using their intellectual strength to the fullest to find a cure.

However, this problem would not arise if we would pull the reins over our gluttony or show some sincerity and real concern for our health and well being.

Medications are being devised to burn fat, to raise metabolism, to curb appetite, to regulate genes and hormones that control fat metabolism.

And one such technique is blocking absorption of fats from the diet which is brought about by a drug with the name Orlistat.

How does Orlistat Help in Weight Loss?

Orlistat is a lipase inhibitor or in simpler terms a fat-absorbing drug.

Its role in weight loss is based on the premise that eating fats makes us fat.

However, that is not totally correct and you can find that out here.

It is derived from the compound lipstatin isolated from bacteria Streptomyces toxytricini and its chemical name is tetrahydrolipstatin.

It is sold as a prescription drug by the name Xenical (120mg) and as an over the counter drug by the name Alli (60mg).

Our stomach and guts secrete a number of enzymes and hormones that aid in the digestion of food.

Ever enzyme acts specifically on a particular food component like amylase act on carbohydrates, lipase acts on fats.

Breaking down of food enhances its absorption in the body.

Our intestine can absorb 95% of the ingested fat and this helps us understand that on a long term diet rich in unhealthy fat can lead to weight gain.

Lipase is an enzyme that digests fat and there are many lipases based on the different organs that secrete them.

Pancreatic lipase is the lipase secreted by the pancreas- the same organ that secretes that insulin.

Lipase inhibitor binds to this enzyme and inhibits its activity. The fats remain undigested and pass out of our body in stools.

It facilitates the removal of all types of fat and prevents around 30% of the fats from being absorbed.

What does this mean?

Orlistat is a compound of bacterial origin. It inhibits the activity of enzyme- lipase and prevents breakdown and absorption of fats. It prevents 30% of ingested fats from being absorbed, thus preventing weight gain.

Science on Orlistat and Weight Loss

Since it is the only lipase inhibitor that has been developed into a drug, a number of clinical trials have been conducted to determine orlistat’s safety and efficacy in weight loss.

1. Research shows that orlistat indeed causes weight loss

Orlistat taken at a dose of 120mg thrice a day results in 200 Calorie deficit per day.  Orlistat, when combined with a low calorie diet, leads to a dose dependant increase in weight loss.

It is found to cause weight loss with decrease in leptin levels- the hormone that regulates appetite and fat deposition.

A clinical trial was conducted in the Netherlands, where subjects were assigned to a 500 Calorie reduced diet (30% calories coming from fats) for four weeks which resulted in a weight loss of 0.5-4 kg.

After that, they were treated with orlistat or placebo along with low-calorie diet for 12 weeks.

Weight loss in the orlistat group was around 4.3 kg while in placebo was 2.1 kg. Gastrointestinal side effects were mild or transient.

Results of a study investigating the safety and efficacy of orlistat for obesity treatment demonstrated a weight loss of 4.65kg and a 4 cm reduction in waist circumference in 24 weeks of treatment.

What does this mean?
Orlistat causes weight loss by absorbing fat which creates a 200 Calorie deficit each day.  It also influences leptin levels which is a hormone that controls appetite and fat accumulation. Orlistat treatment for3 months results in a weight loss ranging from 5-10% of initial body weight.


2. Orlistat is one of the best options for treating diabesity

Diabetes or diabetes-induced obesity is another health problem of growing concern. Diabetes can occur as a risk factor or consequence of obesity.

Insulin not only regulates blood sugar levels but also controls the deposition of fats.

Research claims that orlistat when used as a primary weight loss agent cause modest weight loss in diabetic patients.

The famous Xendos study reported that the risk of developing diabetes was 37.3% lower in orlistat-treated patients.

The risk of developing diabetes was reduced by 45% even in individuals who had impaired glucose tolerance.

In this study, initially for one year, a weight loss of 10.6 kg was seen treatment group whereas the placebo group lost 6.2kg. At the end of years treatment group lost 5.8 kg while the placebo lost only 3 kg.

This result of lowered diabetes risk in orlistat-treated patients is also proven by another study conducted.

What does this mean?
Human studies show that orlistat is effective in causing weight reduction in diabetic patients and also reduces the risk of developing diabetes in obese individuals. The XENDOS study shows that orlistat in combination with low calorie diet can cause twice the weight loss than diet alone.

3. It improves metabolic health

The advantage of orlistat treatment is that it not only causes weight loss but also improves metabolic health especially cholesterol levels.

A review study dating back to 2003 reported a significant decrease in blood pressure and cholesterol with orlistat treatment.

Another review of 28 studies also showed that 6-month treatment with orlistat brings favourable changes in cholesterol levels.

A 24 week study reported that orlistat can be useful for treating hypercholesterolemia- a condition characterized by excessively high cholesterol levels.

In addition, a weight loss of 5-10% and in some cases even more than that was observed.

Another study demonstrated weight loss of 7.4 kg in 6 months with a reduction in cholesterol levels with orlistat treatment.

What does this mean?
Apart from reducing body weight, orlistat also lowers blood pressure and cholesterol.

It helps in weight maintenance

A 1 year long study was conducted at the University of Colorado Health Sciences Center, USA to investigate the efficacy of orlistat in weight management.

Initially, the individuals were kept on a low energy diet for 6 months.

Then they were treated with 30, 60 or 120mg of orlistat thrice a day with maintenance diet for 1 year.
The group receiving 120mg orlistat regained less weight than placebo-treated group. Improvements in cholesterol levels were seen.

Another study  lasting for 1 year demonstrated that orlistat combined with an energy-restricted diet led to a weight loss of 8.5 % of initial body weight. 35% of the treated individuals lost 5% of their body weight while 28% lost at least 10% of their weight.

Around 1/3 of orlistat-treated patients achieved ‘clinically relevant’ weight loss.

Scientists in Switzerland investigated the ‘on/off’ approach of orlistat consumption on weight maintenance. Subjects took orlistat on a voluntary basis and 73% of those who completed the trial maintained 10% or more of their weight loss.

What does this mean?
Studies lasting for a year have shown that orlistat helps in maintaining lost weight and preventing weight regain.

It outshines other weight loss aids

Orlistat’s effect on weight loss is found to be comparable to that of low carbohydrate ketogenic diet.  Differences in cholesterol levels by both interventions are also similar.

A study was conducted to compare the effects of sibutramine (appetite suppressant- Meridia/Reductil) and orlistat on weight loss and other metabolic parameters.

Within 4 weeks of treatment, significant weight loss was observed in both groups.

Weight loss changes were more significant with sibutramine than orlistat. Yet orlistat had an added advantage of improving blood lipid levels and blood pressure.

A clinical trial was devised to determine whether which one of them: orlistat or sibutramine is better in reducing abdominal obesity.

The experimental groups were as follows:

  • Diet and sibutramine (10mg/day)
  • Diet and orlistat (3 x 120mg/day)
  • Diet, sibutramine and orlistat
  • Diet

For reducing BMI, sibutramine therapy was the best followed by a combination of both drugs and lastly orlistat monotherapy.

However, reduction in waist circumference was strongest in orlistat monotherapy.

What does this mean?
Orlistat is as effective as low carbohydrate, ketogenic diet in reducing weight. It is better than sibutramine in reducing abdominal obesity.


A dose of 120 mg of orlistat thrice a day is recommended as optimum for weight loss.  Consult your doctor for an appropriate dosage and treatment duration.


Since orlistat’s mechanism of action is to prevent fat absorption and inhibit the activity of digestive enzymes, a few gastrointestinal side effects are observed  :

  • fecal incontinence
  • flatus
  • oily discharge
  • oily evacuation
  • soft stools
  • Abdominal cramping

However, research  suggests that side effects due to fat malabsorption is seen only in 20% patients and lasts for 1 year.

The symptoms diminish in the second year of treatment.

Studies point out that orlistat may increase the rate of gastric emptying thereby negatively influencing post-meal glucose and insulin levels; this might affect appetite and increase hunger.

Also due to reduced absorption of fats, a deficiency of fat-soluble vitamins may occur.

So it is advisable to take oral vitamin supplements.

Another thing to be kept in mind is that orlistat works best with a low-calorie diet.

Orlistat should be avoided in certain conditions:

  • Pregnancy and lactation
  • Food absorption problems
  • Liver problems
  • Gall bladder problems
  • Thyroid issues
  • Eating disorders

Disclaimer: We strive to provide current and relevant information but drugs/supplements usually impact each individual differently. Thus, it is best to consult your doctor about the side effects, interactions with drugs, and the right dosage.


Orlistat’s efficacy in causing weight loss is well proven by research. It would work well for those who are resistant to weight loss and find it hard to give up on foods rich in fats.

But studies show that orlistat works well only in combination with a low-calorie diet. However, there are some things you can’t miss.

First, you cannot ignore the side effects caused by orlistat. Secondly, it is the unhealthy fats that make you gain weight.

You require healthy fats for the functioning of your body and for the absorption of vitamins. However, orlistat does not discriminate between types of fat and blocks all fat.

Lastly, orlistat may protect you against weight gain by a diet rich in fats but not from the weight gain caused by carbohydrate consumption.

We would suggest you try some natural lipase inhibitors if you are so keen on it. Consult your doctor before taking orlistat.

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