Why No Weight Loss During Treatment?

Last Modified: March 19, 2010

Dear OncoLink "Ask The Experts,"

I am getting radiation therapy for pancreatic cancer. I have been told for years that I am a little overweight, but now they tell me not to lose weight. Why?

Karen Wagner MS, RD, LDN, Clinical dietitian specialist for the Abramson Cancer Center, responds:

This issue is often very confusing for people going through treatment. There are a number of good reasons though not to loose weight during treatment. Particularly for people going through radiation treatment, the way the doctors and technicians treat you is based upon a small treatment field or area. When you loose more than about 10 % of your weight, the team may need to stop treatment to make sure that the area they want to treat is still in the correct position. Additionally for anyone who will possibly be getting surgical resection after treatment, weight loss is associated with more complications after surgery. We want to keep you in the best possible condition to get through any other treatments that you may need after radiation.

Another important reason is that when people loose weight during cancer treatment they tend to loose more muscle mass than fat mass. People tend to be less active and they need more protein to heal and rebuild cells. This results in the body breaking down more muscle than it would under normal conditions of weight loss. By not loosing weight, you can help preserve your lean muscle mass.

The last reason I will touch on is that weight loss is associated with worse side effects of treatment and that may mean that your team will need to stop and re-evaluate their treatment plan for you if it appears that it is too toxic. Cancer treatment is not easy and we want to support you the best we can. We watch weight closely as an indicator of how well we are supporting you through your treatment.

This question and answer was part of the OncoLink Brown Bag Chat Series, Exercise, Nutrition and Cancer Webchat. View the entire transcript here.