Anti-obesity orlistat and colorectal cancer risk

A few weeks ago, a middle-age patient who has been taking orlistat regularly for weight loss asked about the increased risk of developing cancer, especially colon cancer, with prolonged intake of the product.

Orlistat, which is available locally under different brand names, is the only anti-obesity drug approved for over-the-counter sale. When a drug is approved as such, that means there’s no significant risk for people to take it even without a doctor’s prescription.

For those who have taken the product, they know that it is a potent inhibitor of the absorption of dietary fats in the intestines. Hence, one needs to go to the bathroom shortly after eating a fatty meal because the fat goes down the gut with reduced absorption and has to be passed out. Therefore, common side effects experienced by those who take it include oily stools, fecal spotting, diarrhea and abdominal pain.

I remember a patient telling me this about her experience with orlistat: “I don’t trust it when I fart, because almost always, something goes with it.”

Despite the “small accidents” one can have with orlistat, a lot of patients doctors prescribed it to seem not to mind because they get the kind of waistlines they want.

It has been shown to be effective in reducing weight and  waist circumference at the same time improving levels of blood pressure, cholesterol and blood sugar. There are studies showing it may also help in preventing the development of type 2 diabetes.

So everything seems to be well on the waist-reduction front with orlistat until a study got published suggesting a risk for colon cancer development related to the drug. Researchers S.B. Garcia, L.T. Barros, A. Turatti et al. reported in 2006 that in preclinical studies using experimental rats, orlistat was associated with increased numbers of cells believed to be potential precursors of colon cancer. They called these cells as “aberrant cryptic foci.”  The experts were divided whether or not these are real precursors of colon cancer.

US FDA conclusion

However, the various clinical trials involving orlistat didn’t show any red flag as to the possibility of developing cancer. And after pooling all data, the United States Food and Drug Administration concluded that there was no evidence of a causal link between the use of orlistat and the risk of colorectal cancer.

For those who may still have some apprehensions with the use of orlistat, a recent population-based study by J.L. Hong et al. published two months ago in the British Medical Journal also concluded that there’s no evidence that starting treatment with the drug raises the risk of developing colorectal cancer; well, at least in the short term.

The researchers aimed to examine the risk of colorectal cancer after orlistat initiation in the United Kingdom’s population. The study involved 33,625 adults aged 18 years or over who started treatment with orlistat. Each orlistat initiator was matched to up to five non-initiators (n=160,347) on age, sex, body mass index and calendar time.

According to the authors, orlistat initiators were more likely to have a previous history of diabetes or hypertension and to receive prescriptions for anti-diabetes drugs, statins and aspirin compared with non-initiators. The authors reported that in the data analysis, there were 57 colorectal cancer events among orlistat initiators and  246 among non-initiators. The median follow-up times were 2.96 and 2.86 years, respectively, for orlistat initiators and non-initiators.

There was no statistically significant difference in the risk of developing colorectal cancer in orlistat initiators compared to non-initiators.

One limitation of this study is that the observation or follow-up period was only around three years. It’s true it may take a longer time to develop clinically apparent colorectal cancer.

For those who don’t find the clinical data on orlistat reassuring enough, going back to the mainstay of treatment of overweight and obesity is the best option. The good old diet and exercise still remain the best strategies in effectively and safely reducing weight.

Basic weight-loss regimen

To summarize a basic weight-loss regimen:

One must reduce the amount of fat in the diet by limiting it to no more than 25 to 35 percent of total calories. A high-fat diet by itself is linked with the development of colon cancer. A diet rich in fruits, grains, vegetables and lean protein—avoiding overconsumption of saturated fat from animal meat and trans fats—would be ideal.

One must also maintain a normal weight through regular exercise, consisting of at least four days of exercise per week, at least 30 minutes each session. Leisurely walking may not be good enough. One must aim for at least moderate intensity exercise, which could increase the heart rate and breathing rate. To sustain the habit, one must choose an exercise one enjoys.

If one is taking orlistat, I don’t think the available data warrant discontinuation of the drug. It would be prudent though to consult one’s doctor about lowering the dose of orlistat to achieve one’s weight goals, along with diet and exercise.