Understanding Weight Loss Caused by Chemotherapy

Despite what you've heard, weight loss is not a given

Weight loss may seem like the silver lining of chemotherapy, but the truth is that not everyone on treatment loses weight. It's one of the false impressions we've gotten from the media, where the person with cancer looks thin and frail. Although it is possible to lose weight, it is certainly not everyone's experience.

Person standing on scale
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Everyone responds differently to chemotherapy, and there are many factors that play a role in how treatment will affect your weight.

Understanding your nutritional needs and the possible side effects of treatment are the first steps to ensuring you maintain your ideal weight during the course of chemotherapy.

This article will review why weight loss happens during chemo and how to manage your weight during treatment.

Factors Contributing to Weight Loss

When people lose weight during cancer treatment, it is often due to an inability to maintain good nutrition. Chemotherapy might cause nausea and a general loss of appetite, while vomiting and diarrhea can greatly impact your ability to retain nutrients from the foods you eat. If someone is constipated, they may not be hungry.

At times, foods can taste and smell very differently due to cancer treatment. For this reason, many specialists recommend limiting your favorite foods as any changes in taste or smell will be more profoundly perceived, creating an aversion to them even after treatment is complete.

Mouth sores can also be a side effect of chemotherapy. Having them on your gums, throat, tongue, or inner cheek can make eating certain foods extremely difficult, exacerbating the pain you may already be feeling. Spicy, salty, or sour foods are especially problematic.

Managing Weight During Chemo

One of the main goals you should strive for during chemotherapy is to keep your weight stable. Even If you are overweight, your healthcare team may not want you to start losing. You can, however, focus on having a more healthy diet, which you can carry over post-treatment to reach your ideal weight.

If your healthcare provider approves, work together to create an exercise plan to meet your fitness needs. Walking, yoga and other forms of exercise are not only ideal ways to keep fit, but they can also help relieve stress, elevate your mood, and even reduce fatigue.

Overexertion is not advised as it can wear you out and cause inflammation that can worsen any side effects you may be experiencing.

Working with a dietitian experienced in cancer therapy can be highly beneficial. A professional trained in the nutritional needs of a person with cancer will be more able to formulate, monitor, and adjust your diet as you move through treatment. Many cancer centers have a nutritionist on staff or can refer to a certified professional in your area.


Good nutrition is essential during chemotherapy. If your caloric intake is too low, it can lead to weight loss and can leave you feeling unable to cope physically and mentally with your treatment

In addition to good nutrition, physical activity can also be beneficial if approached wisely and under the supervision of a medical professional. Even a little outdoor activity (such as gardening) can prevent the loss of lean muscle mass key to maintaining strength and mobility.

Good planning, a balanced diet, and a moderate approach to fitness are three things you need to ensure you meet your health goals during chemotherapy. 

A Word From Verywell

Good nutrition is so important during cancer treatment. It can be a stressful time for your body. Ensuring it has the things it needs to perform at its best can help you feel better. If you're unsure of what to eat or how to get started, contact your healthcare team, and they can provide you with resources.

Frequently Asked Questions

  • Do most people gain or lose weight during chemo?

    It all depends on the chemo medicines. Some chemo drugs are likely to cause swelling in the body, leading to weight gain. If steroids are prescribed with chemo, they can increase appetite. Some chemo medications may lead to weight loss due to decreased appetite and taste changes.

  • What types of cancer cause the most weight loss?

    One study found that the most cancers associated the most with weight loss include:

    • Prostate cancer
    • Colorectal
    • Lung
    • Gastroesophageal
    • Lymphoma
    • Pancreatic
  • How fast is weight loss in cancer?

    This can vary for each individual, based on their cancer type. Generally, any unintentional weight loss needs to be reported to a healthcare provider, so they can investigate the cause.

  • What happens if you lose too much weight during chemo?

    Losing too much weight during chemo may cause the oncologist to hold the chemo treatment or reduce the dose. Too much weight loss can be dangerous and lead to complications if not managed properly.

6 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  2. Chaveli-lópez B, Bagán-sebastián JV. Treatment of oral mucositis due to chemotherapy. J Clin Exp Dent. 2016;8(2):e201-9. doi:10.4317/jced.52917

  3. Sánchez-lara K, Ugalde-morales E, Motola-kuba D, Green D. Gastrointestinal symptoms and weight loss in cancer patients receiving chemotherapy. Br J Nutr. 2013;109(5):894-7. doi:10.1017/s0007114512002073

  4. LeVasseur N, Cheng W, Mazzarello S, et al. Optimising weight-loss interventions in cancer patients—A systematic review and network meta-analysisPLOS ONE. 2021;16(2):e0245794. doi.org/10.1371/journal.pone.0245794

  5. Cancer.Net. Weight gain.

  6. Nicholson BD, Hamilton W, O’Sullivan J, Aveyard P, Hobbs FR. Weight loss as a predictor of cancer in primary care: a systematic review and meta-analysisBr J Gen Pract. 2018;68(670):e311-e322. doi: doi.org/10.3399/bjgp18X695801

By Julie Scott, MSN, ANP-BC, AOCNP
Julie is an Adult Nurse Practitioner with oncology certification and a healthcare freelance writer with an interest in educating patients and the healthcare community.

Originally written by Lisa Fayed