There's no way to know in advance whether someone will gain weight on a certain drug, or whether a slightly different compound will have a different effect on the waistline — or rather on the brain and appetite centers that contribute to that waistline. In fact, a drug that makes one person pile on pounds could suppress the appetite in another patient.
While taking antidepressants known as SSRIs, for example, which include drugs such as Prozac and Zoloft, some people gain weight, some lose it and others see no change, says Lawrence J. Cheskin, M.D., director of the Johns Hopkins Weight Management Center and an associate professor at the Johns Hopkins Bloomberg School of Public Health.
Diabetes drugs also can make people gain, which Duke diabetes expert Lien notes is ironic because obesity is associated with diabetes in the first place.
Of course, a drug may not be the only reason for weight gain. The stress and pain of being ill can make people eat more and exercise less. Cheskin says it's important to look at the whole picture — diet, drugs, exercise, lifestyle.
If you gain five pounds, that added weight may or may not be related to the medicine you're taking, Cheskin says.
None of this means that patients can't or shouldn't take drugs in these categories. But it does mean they need to discuss weight issues with their physicians, and educate themselves, too, about side effects, says Harvard's Blackburn. That's particularly important for people who are already overweight, or who have had ups and downs with their weight in the past.
Usually, the physician will be able to find another drug that works without adding pounds. For instance, Lien says metformin (also known as Glucophage) is often preferred for diabetics and it doesn't carry the same risk of added weight as insulin and several other diabetes drugs.