Q: I take medications for high blood pressure and high cholesterol. I am also obese, which is another risk factor for heart disease. Should I be on a weight-loss drug?
A: You're right that being obese can put a heavy burden on your heart. It boosts your heart attack risk by about 60 percent. Diet and exercise are always the first steps toward controlling excess weight and other heart disease risk factors.
When lifestyle changes aren't enough, doctors often prescribe medications, like statins for high cholesterol. But the medical options for weight loss are more limited.
What's more, weight-loss drugs are only moderately effective. On average, they help people lose about 5 percent of their body weight over a period of six to 12 months. But the response varies widely. Some people may lose a lot of weight on a particular drug. Others may lose little or none.
And we don't yet have the tools to determine who will do well on a particular drug and who won't. So it's trial and error.
You may be a good candidate for a weight-loss medication if you have a body mass index (BMI) higher than 30, which is considered obese. (Go to www.health.harvard.edu/bmi to calculate your BMI.)
You may also benefit if you have a BMI of 27 or higher along with health problems related to your weight. These include Type 2 diabetes, sleep apnea, high blood pressure or chronic joint pain.
Finally, you may need weight-loss drugs if you are overweight and have been unable to lose weight despite eating a healthy diet and exercising regularly.
There are several FDA-approved weight-loss drugs on the market. I've put a table listing these drugs and how they work on my website, AskDoctorK.com.
In some cases, health conditions other than obesity influence which medication your doctor will prescribe. For example, a person with Type 2 diabetes might benefit from liraglutide (Saxenda). This injectable medication is also used to treat diabetes.
On the other hand, a person with a fast heartbeat shouldn't take phentermine (Adipex-P, Ionamin). This drug can speed up the heart.
As a general rule, you must lose at least 5 percent of your weight within three months in order to keep taking a particular weight-loss drug. If you don't, your doctor may prescribe a different drug, or a combination of two or more drugs.
Because weight-loss medicines have not proven dramatically effective, and because some new medicines have caused serious health problems, many doctors think it is a pipe dream to believe we will ever have a drug that safely and powerfully helps us to lose weight.
I'm more optimistic. Scientific research in the past 20 years has made major advances in understanding the body chemistry that controls weight and appetite.
It wouldn't surprise me if that research leads to powerful and safe weight-loss drugs in the next 20 years.
However, a healthy diet and regular exercise are always going to be important, too.
• Dr. Anthony Komaroff is a physician and professor at Harvard Medical School. To send questions, go to AskDoctorK.com, or write: Ask Doctor K, 10 Shattuck St., Second Floor, Boston, MA 02115.