Will I lose weight during chemotherapy?

Losing weight during chemotherapy treatment is very common. There are many factors that can contribute to weight loss while undergoing chemo. In the first few paragraphs, we’ll provide quick answers to common questions about losing weight during chemotherapy.

Quick Answers

Will I definitely lose weight during chemo? It’s very likely, but not guaranteed. Around 80% of people lose weight during chemotherapy.

How much weight will I lose? Most people lose between 5-10% of their body weight over the course of treatment. So someone who weighs 150 pounds may lose 7-15 pounds.

Why does chemo cause weight loss? There are several reasons chemo can lead to weight loss, including loss of appetite, changes to metabolism, fatigue, nausea, and mouth sores.

Is the weight loss permanent? Some of the weight loss may be muscle mass and fat, which can be regained after treatment. But losing weight is common and expected.

Should I be worried about losing weight? Mild weight loss is normal, but significant loss can be dangerous. Tell your care team if you lose more than 10-15 pounds.

What can I do to maintain my weight? Eat nutrient-dense foods, stay hydrated, exercise if possible, and ask your doctor about medications to stimulate appetite.

Why Does Chemotherapy Lead to Weight Loss?

There are several reasons why chemotherapy frequently causes weight loss in patients. Understanding the potential mechanisms behind chemo-related weight loss can help patients know what to expect and how to try to counteract it.

Loss of Appetite

One of the most common side effects of chemotherapy is a substantial decrease in appetite. Many of the chemotherapy drugs are designed to kill rapidly dividing cancer cells, but they can also damage healthy cells in the process. The cells in the digestive tract and gut are often affected, leading to mouth sores, nausea, vomiting, and loss of appetite.

Even powerful anti-nausea medications don’t always completely eliminate chemo-related nausea. The nausea and intestinal discomfort makes it physically difficult to eat enough, leading to decreased food intake and subsequent weight loss.

Changes to Metabolism

There is evidence that chemotherapy drugs themselves – as well as the cancer itself – can increase the body’s metabolic rate. A higher metabolism causes the body to burn through calories faster, which can lead to weight loss if calorie intake is not increased to match.

In addition, chemotherapy is known to cause dehydration and electrolyte imbalances. Maintaining proper hydration is important for health, and dehydration can also suppress appetite, leading to reduced food intake.

Fatigue & Weakness

Fatigue and general weakness are extremely common during chemotherapy. This severe tiredness makes basic daily tasks take much more energy. Something as simple as shopping for and preparing food can become exhausting.

Between the fatigue and weakness, patients undergoing chemo treatment often turn to easygrab pre-packaged snacks and meals rather than cooking full nutritious meals. Relying on this type of convenience food tends to reduce overall calorie intake, resulting in weight loss.

Mouth Sores

Chemotherapy frequently causes painful mouth and throat sores. Any irritation to the soft tissues of the mouth or GI tract can make eating physically uncomfortable. Attempting to eat can become so painful that cancer patients involuntary reduce their food intake just to avoid aggravating the mouth sores.

Loss of Muscle Mass

Being largely inactive during cancer treatment contributes to muscle mass loss. Bed rest and low activity allow the body to catabolize muscle proteins. Loss of strength and muscle mass makes daily functioning more difficult and requires less energy expenditure.

The combined effect of reduced appetite, nausea, fatigue, and inactivity creates a catabolic state in the body that causes weight loss and muscle wasting.

How Much Weight Will I Lose During Chemotherapy?

The amount of weight lost while undergoing chemotherapy treatment varies widely based on the individual. However, there are some general statistics that provide an idea of typical weight loss patterns:

  • Around 20-80% of people with cancer experience weight loss during chemotherapy treatment.
  • The average amount of weight lost is approximately 5-10% of body weight.
  • So for a 150 pound person, expected weight loss would be 7-15 pounds.
  • Weight loss of more than 10-15% of body weight is considered potentially dangerous.

These averages help provide a rough estimate, but many factors affect exactly how much weight an individual will lose. The type of cancer, chemotherapy regimen, nutrition, hydration, exercise, and medications can all impact weight fluctuations.

It’s impossible to predict exactly how much someone will lose during chemo. Checking weight at each appointment can allow the healthcare team to monitor significant changes and intervene if needed.

Weight Loss by Cancer Type

Some general statistics on weight loss experienced during chemotherapy based on cancer type:

  • Breast cancer: 27-100% experience weight loss; average 4-11 lbs
  • Gastrointestinal cancers: 83-87% experience weight loss; average 10-20 lbs
  • Lung cancer: Weight loss in 55-90%; average 14 lbs
  • Gynecological cancers: Up to 85% have weight loss
  • Hematological cancers: 27-48% have significant weight loss
  • Head and neck cancers: 90% with weight loss; average 9-18 lbs

As shown, the rate and amount of weight loss depends heavily on the type and location of cancer being treated. But these ranges demonstrate that most patients undergoing chemotherapy can expect to lose at least some weight.

Is Weight Loss Preventable During Chemo?

Can weight loss be prevented during chemotherapy treatment? While it is very common, weight loss is not an absolute certainty. There are some proactive steps patients can take to try to maintain weight during chemotherapy:

Eat More Calories

Increasing calorie intake to account for a higher metabolism and loss of appetite is important. Eating smaller, more frequent meals with nutrient-dense foods can help maximize calories.

Control Nausea

Discuss anti-nausea medication options with your care team to minimize appetite loss. Medications like Zofran or medical marijuana can be very helpful.

Choose Nutritious Foods

When eating is difficult, focus on getting essential nutrition through smoothies, shakes, eggs, nut butters, and other nutrient sources.

Exercise If Possible

Any physical activity, even light walking, helps maintain muscle mass and appetite. But don’t over-exert yourself when fatigued.

Stay Hydrated

Drinking water, broths, electrolyte beverages can prevent dehydration and subsequent appetite loss.

Ask About Medications

Medications like Marinol, megace, or medroxyprogesterone can help stimulate appetite. Discuss options with your doctor.

While these tips can help, they don’t always prevent weight loss completely. But being proactive provides the best chance of maintaining weight.

Is Losing Weight During Chemo Dangerous?

Mild weight loss of 5-10% of body weight is common and expected with chemotherapy. Losing this modest amount of weight is usually not dangerous. However, more significant weight loss can be concerning.

Losing more than 10-15% of total body weight rapidly is considered excessive and may indicate an underlying problem. Significant unintended weight loss usually warrants further evaluation to identify the cause. It may be necessary to adjust medications, provide nutritional support, or take other steps to slow or halt further weight loss.

Why Rapid Weight Loss Can Be Dangerous

There are a few reasons why significant weight loss during chemotherapy can be dangerous:

  • Malnutrition – Weight loss can indicate inadequate calorie and nutrient intake, leading to nutritional deficiencies.
  • Reduced strength – Losing muscle mass reduces physical abilities and stamina.
  • Immune suppression – Malnutrition negatively affects the immune system, which is already compromised during chemo.
  • Organ dysfunction – Rapid weight loss stresses the organs and impairs their function.
  • Emotional distress – Body changes from weight loss can negatively impact self-image and emotions.

Catching excessive weight loss early allows prompt intervention to reverse it. Nutritional counseling, exercise, appetite stimulants, and meal programs can help stabilize body weight if needed.

Does the Weight Come Back After Chemo?

Many patients wonder if they will regain the weight dropped during chemotherapy after finishing treatment. The answer varies based on individual circumstances:

  • Lost fat and muscle mass can gradually return to normal when appetite improves.
  • But some weight loss may be permanent if it resulted from surgery or intestinal changes.
  • Some patients may actually gain back more weight than they lost.
  • Estrogen therapy in women often leads to increased fat deposition after chemo.
  • Steroids taken during treatment can also increase fluid retention.

Overall, mild weight loss of up to 10-15 pounds is usually not permanent. While the lost weight tends to come back, it may balance out at a new normal body weight.

Gaining Weight Back Healthily

Here are some tips for regaining weight in a healthy way after chemotherapy:

  • Focus on nutrient-dense foods like avocado, nuts, olive oil for healthy fats
  • Eat plenty of lean proteins like chicken, fish, eggs, beans
  • Choose whole grains like brown rice, quinoa, oats
  • Fill up on fruits, vegetables, yogurt for fiber and nutrients
  • Stay active with walking, swimming, stretching
  • Work with a nutritionist or registered dietitian
  • Make dietary changes gradually

What Should I Eat During Chemo Treatment?

Maintaining good nutrition during chemotherapy helps patients better tolerate treatment and side effects. Here are some eating strategies that can help:

Focus on Calorie-Dense Foods

Getting enough calories each day from nutrient-rich foods provides energy for healing. Examples include:

  • Eggs
  • Full-fat dairy products
  • Avocados
  • Nuts, nut butters
  • Yogurt
  • Olive oil
  • Protein shakes

Eat Small Meals Frequently

Large meals may seem unappetizing when nauseated or fatigued. Eating smaller amounts every 2-3 hours helps maximize caloric intake.

Stay Hydrated

Drink plenty of water, electrolyte beverages, broths, juices, and smoothies. Dehydration suppresses appetite.

Focus on Nutrient Absorption

Choose cooked foods over raw, ground meats over steak, and cooked vegetables for easier digestion and absorption.

Reduce Fiber Temporarily

High-fiber foods can irritate the GI tract. Stick to white bread, white rice, pasta, and cooked vegetables.

Avoid Problem Foods

Stay away from overly sweet, fatty, or spicy foods if they trigger nausea or diarrhea.

Supplement If Needed

Nutritional supplements or shakes can provide extra calories and nutrients if appetite is poor.

Tips for Coping with Chemo-Related Weight Loss

Handling the weight fluctuations that come with chemotherapy treatment isn’t always easy. Here are some tips to help cope physically and emotionally:

  • Weigh yourself only once per week or as directed by your care team.
  • Focus on eating nutrient-dense foods rather than counting calories.
  • Accept that weight changes are temporary and do not reflect on you.
  • Exercise moderately to maintain muscle tone and fitness.
  • Communicate openly with your care team about concerns with weight change.
  • Join a support group to share common experiences.
  • Express your feelings to loved ones and ask for support.
  • Focus on the benefits of chemo rather than the temporary side effects.
  • Buy comfortable, loose-fitting clothing that accommodates weight fluctuations.
  • Make diet and fitness changes slowly and gradually once treatment ends.

When to Contact Your Care Team About Weight Loss

Routine monitoring of weight during chemotherapy provides important data to your cancer care team. In general, contact your doctor or nurse if:

  • You lose more than 5-10 pounds in one week
  • You lose more than 10-15% of your body weight overall
  • Appetite doesn’t improve within 2-3 days after chemotherapy
  • Nausea or vomiting persists more than 24 hours after chemo
  • You become physically weak, dizzy, confused from nutritional deficits
  • Normal foods become difficult to physically swallow comfortably

Significant or rapid weight loss sometimes necessitates a reduction or delay in chemotherapy dosing if there are concerns about malnutrition. Catching weight changes early allows for prompt intervention to stabilize nutrition and body weight while undergoing cancer treatment.


Weight loss during chemotherapy is extremely common, affecting around 80% of cancer patients undergoing treatment. Typical weight loss ranges from 5-15% of body weight, though the amount varies individually based on many factors.

There are several mechanisms that explain why chemo often leads to weight loss, including appetite changes, nausea, fatigue, metabolic shifts, dehydration, and loss of muscle mass. While mild weight loss is expected, losing more than 10-15% of body weight can become dangerous.

Preventing weight loss altogether is difficult, but staying hydrated, controlling nausea, exercising, and eating nutrient-dense calories can help minimize loss. Some of the weight lost during chemo is able to be regained after treatment ends as appetite and strength return.

Monitoring your weight, maintaining good nutrition, and reporting significant weight changes to your care team allows steps to be taken to keep weight stable during chemotherapy treatment.

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