Does Coumadin (warfarin) affect your metabolism and cause weight gain?

My wife has been taking warfarin for over two months. When she started exercising for three days a week, in a month's time she has gained 12 pounds, and her diet did not change. Before she started exercising she was losing some amount of weight. She will be using warfarin for the next four months. Do you think warfarin has affected her metabolism? If yes how could she lose weight then?

The Health meets Food Team Says...

This is a very interesting question. There is no evidence that Coumadin® (warfarin) causes weight gain all by itself.  It is important to consider whether there is a medical issue that is leading to your wife's weight gain. It is key that she discuss this with her doctor. Perhaps there is another medication that she is taking that could lead to weight gain. Some people who take Coumadin for certain heart problems are more susceptible to congestive heart failure and that is the sort of issue her physician would want to know about.

The trouble with teasing out whether Coumadin causes weight gain is that when people start taking Coumadin, their diet changes. Often people will stop eating as many vegetables as they used to because so many common vegetables are high in Vitamin K. Vegetables have a low caloric density, meaning there are comparatively few calories in them by weight. You can eat quite a lot of them without eating many calories. (Compare this to potato chips, chocolate, or even breads.) Often people will replace the vegetables they were accustomed to eating with foods that are more calorie-dense, and as a result they gain weight. As little as 300+ more calories per day leads to weight gain, but because the volume of food they're eating is simliar to what they're used to, it seems that the only difference is that they're taking Coumadin. Sometimes a close look at what you're eating can reveal the small changes that are leading to weight gain.

Weight loss is accomplished in two ways: 1) by eating fewer calories and exercising more and 2) eating high quality calories.

The good news is that those same small changes can lead to weight loss. It can be a challenge when the amount and type of vegetables you eat is limited by your intake of Vitamin K, but often you can find vegetables that are low in Vitamin K - like zuchini, for example - that you'll enjoy as much as the vegetable you can't eat quite as often.

Often people will use supplements like sports drinks and the like while they are exercising, and these can be useful for those who exercise strenuously, but for many people they are actually just added calories. Keeping a food diary is a good first step for your wife. This can help her to get an idea of what she is eating.

Many times asking one's doctor for a referral to the dietitian can help and having the food diary can be an aid to helping create a diet that works for your wife.

Reviewed 08/21/2022

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