Jennifer was not in a good mood. "Doctor, I am getting fat! Look at me. I have been eating like crazy. I do not understand this. Do you think that it has anything to do with those antidepressants that the psychiatrist gave me? My boyfriend thinks so. I've been overweight my entire life, the last thing I need is to gain more weight." Jennifer was understandably distressed. Her boyfriend had hit the nail on the head! Her increased appetite and subsequent weight gain resulted from the antidepressants that she was taking. She was weaned off them and she is gradually losing her excess weight.

Research conducted by Dr Louis Aronne, director of the Comprehensive Weight Control Program at New York - Presbyterian Hospital /Weill Cornel Medical Center and past president of the North American Association for the Study of Obesity, suggests that fewer than five per cent of overweight Americans got that way because of their medications. Although the figure is not great, it is a cause for concern because of the increasing number of chronic illnesses that are treated with drugs.

Certain prescription drugs used to treat depression, mood disorders, psychotic behaviour, seizures, migraines, diabetes, cancer, high blood pressure and heartburn can cause weight gain - sometimes up to 10 pounds a month. In addition, corticosteroids such as prednisone (taken by people with severe allergies, asthma or arthritis), hormone replacement therapy, oral contraceptives and even over-the-counter antihistamines can cause you to gain weight. While no one knows exactly how many prescription drugs can cause weight gain, experts estimate the list includes more than 50 common medications.

So how do these drugs do this? In many and varied ways. Some antihistamines increase weight by making you lethargic or sleepy - that means you will burn fewer calories throughout the day. The anti-psychotics, for example haloperidol and clozapine, affect metabolism and can add as many as five pounds a week. Insulin and anti-diabetic drugs known as sulphonylureas can induce hypoglycemia (low blood sugar) which in turn stimulates appetite. A class of antidepressants, SSRIs, target the mood and appetite-related neurotransmitter serotonin and may cause weight gain.

It is almost impossible to predict the weight gain during treatment because our various body chemistries cause us to react differently to drugs. To confuse the issue, any medication can cause changes in weight.

If you gain five or more pounds in a month without overeating or decreasing your exercise, your medicine cabinet may be at the root of the problem, particularly if you recently started a new medication. At that point, you can check the package insert or ask your pharmacist if weight gain is among the side effects of your medication. Even if you suspect a prescription medication is causing weight gain, never stop taking the drug without consulting your doctor, because stopping some of these medications on your own can have very serious consequences. In many cases, the doctor will be able to switch you to another medication that has the same desirable effects but which will not cause weight gain. No one should be complacent because drugs that lead people to put on just 10 or 20 pounds a year, if taken for many years, can add up to big problems over time.

Growing concern about weight side effects from anti-psychotics prompted a joint panel of the American Psychiatric Association, the American Diabetes Association and other medical groups to issue a consensus statement urging doctors to monitor weight in patients who are taking them, and to consider switching medications for patients whose body weight increased by five per cent or more.

What to do ?

You can take steps to help work off any excess pounds. Keeping a food diary of what you eat and when you eat it is probably the best behavioural tool for losing weight. Dr George Blackburn, associate director of the division of nutrition at Harvard Medical School, where he teaches a course on drugs and weight gain, says eating 100 to 200 fewer calories each day is enough to counteract the kind of weight gain you would experience while taking most drugs, especially if you increase your exercise .

Why not buy a pedometer and start walking. You burn off 100 calories with every 2,500 steps - that may just be enough to offset any drug-induced weight gain.

Dr Jacqueline E. Campbell is a family physician in private practice.
E-mail drjcampbell14@yahoo.com

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