Weight Loss with Cancer: Causes and Nutrition Tips

Dr. Boris Wydoff

Weight Loss with Cancer: What Should You Do First?

Weight loss with cancer can be linked to reduced appetite, treatment side effects and changes in metabolism. It is important not to wait until the weight loss becomes obvious to others. Start monitoring your body weight regularly, pay attention to your appetite and muscle strength, and try to get enough protein and energy. Be sure to tell your oncologist if your weight continues to drop, even if you still feel reasonably well.

Start with three steps:

1. Monitor your body weight. Weigh yourself regularly, preferably using the same scales and under the same conditions. Keep a record of the results so you can track changes rather than relying only on your appearance or how your clothes fit.

2. Watch for warning signs. Rapid weight loss, reduced muscle strength, loss of appetite, feeling full quickly and persistent weakness are all reasons to inform your oncologist. Do not wait until you become severely malnourished.

3. Support your nutrition starting today. If you cannot manage a normal-sized portion, divide it into several smaller meals. For example, eat an egg with cottage cheese, add milk to your porridge, or include fish, yogurt and other protein-rich foods that you can tolerate.

The main goal is not simply to regain your previous weight, but to preserve muscle, provide your body with energy and help it cope with treatment more easily. At the same time, it is essential to find out why you are losing weight. Sometimes the problem is not just inadequate food intake but also changes in metabolism.

Why Do People Lose Weight with Cancer?

Weight loss during cancer can happen gradually or quite rapidly. You may notice that your clothes have become looser, you no longer feel like finishing your usual portions, and physical activities that once seemed easy have become difficult. Sometimes fat tissue decreases, sometimes muscle is lost, and sometimes both happen at the same time.

Doctors identify several mechanisms behind this condition. One is inadequate nutrient intake: you eat less than your body needs. Another is a change in metabolism, in which your body uses more energy than it receives.

It is especially important to distinguish ordinary weight loss from cancer cachexia. Cachexia is a complex syndrome involving the loss of muscle and fat tissue, weakness and metabolic changes. It can develop even when a person continues to eat normally.

That is why simply increasing the amount of food you eat is not always enough. If your body is losing muscle and strength, we need to understand why this is happening and find a comprehensive way to support you.

How Does Weight Loss Happen with Cancer, and What Causes It?

The causes may be related both to the disease itself and to anticancer treatment. Several factors can affect the same person at once, so there is no single explanation that applies to every patient.

One common cause is reduced appetite. Food no longer makes you want to eat as it used to, certain products may start to seem unpleasant, and the smell of cooking can make you feel nauseated. As a result, you get fewer calories and less protein than your body needs to maintain its strength.

Another factor is treatment side effects. Chemotherapy can cause nausea, vomiting, diarrhea, constipation, dry mouth and changes in taste. Sometimes painful sores develop in the mouth or throat, making swallowing difficult.

Some patients struggle with early fullness. They eat very little and already feel that their stomach is full. Even when they want to eat, finishing a normal portion becomes difficult.

Pain, anxiety, low mood and constant fatigue also play a role. When you sleep poorly, experience discomfort and feel emotionally overwhelmed, preparing food and eating can become an additional burden.

There are also factors related to the location of the tumor. For example, cancers affecting the digestive system can make it difficult to eat and absorb nutrients. Nutritional problems are particularly common when the intestines, stomach, pancreas or liver are affected.

Is Weight Loss Inevitable with Cancer?

No. Having cancer does not mean that you will necessarily lose weight. Your body's response depends on the type of cancer, its specific characteristics, your overall health and the treatment you receive.

Some patients maintain their usual weight throughout treatment. Others lose weight, while some actually gain it. Certain types of hormone therapy and some medications can increase appetite and cause fluid retention.

That is why the same number on the scales does not always indicate the same state of health. For example, weight gain may be caused not by muscle and nutritional recovery but by fluid accumulation.

Sudden weight loss with cancer requires particular attention. Do not assume that it is simply due to stress, age or poor appetite. Even if you continue eating, changes in your body weight should be discussed with your treating specialist.

Severe weight loss during cancer should not be viewed as an inevitable part of the disease either. The sooner we identify the causes of inadequate nutrition and muscle loss, the sooner we can provide appropriate support.

What Kind of Weight Loss with Cancer Should Raise Concern?

Your appearance alone is not enough to assess the situation. Some people do not notice changes for a long time, especially if their weight tends to fluctuate. Others first notice the problem when their clothes become loose, their arms and legs look thinner, or they feel unusually weak.

Rapid weight loss with cancer is particularly concerning when accompanied by a worsening appetite, constant fatigue and reduced muscle strength. You may find it harder to climb stairs, walk your usual distances or do household chores.

Pay attention to other changes as well:

• Food has become less appealing than before;
• You feel full after just a few spoonfuls;
• You regularly experience nausea or vomiting;
• Your sense of taste has changed;
• You have difficulty chewing or swallowing;
• You have a dry mouth or soreness in your mouth;
• Digestive problems have become more frequent;
• Your usual physical activities have become harder to manage.

None of these signs alone establishes a diagnosis. For example, weakness may be related to anemia, treatment side effects, sleep problems or inadequate nutrition.

Your doctor will assess not only your body weight but also how it has changed, your eating habits, muscle strength, accompanying symptoms and examination results. If necessary, a clinical nutrition specialist will be involved in your care.

What Works for Maintaining Strength During Cancer Treatment? How Should You Eat?

When you have cancer, you sometimes need to rethink your usual ideas about healthy eating. During treatment, your body may need more energy and protein than the body of someone without the disease. Overly strict dietary restrictions can make nutrient deficiencies worse.

The main goal is to provide your body with enough calories, protein, fats, carbohydrates, vitamins and minerals. Your diet should be tailored to the foods you can tolerate, the condition of your digestive system and the recommendations of your medical team.

1. Eat Smaller but More Nutritious Meals

If your appetite has decreased, do not try to finish a large plate of food in one sitting. Instead, have several small meals throughout the day. This is particularly important if you feel full quickly or experience nausea after eating.

For example, instead of having one large breakfast, divide your usual portion into several smaller parts: eat a little porridge first, then have some cottage cheese or yogurt later. You can also have small snacks between main meals.

The important thing is not to rely on empty snacks that take up space in your stomach but provide very few nutrients. Choose foods that contain protein and energy.

2. Include a Source of Protein in Every Main Meal

Protein is essential for maintaining muscle tissue. When you are losing weight, it is particularly important not to let your diet consist mainly of tea, bread, vegetable dishes and small amounts of porridge.

Good sources of protein include:

• Eggs;
• Cottage cheese and other dairy products;
• Plain yogurt;
• Fish;
• Legumes;
• Nuts;
• Tofu.

Try to spread protein-rich foods throughout the day rather than leaving all your protein intake until dinner. For example, you could have an egg and cottage cheese for breakfast, fish for lunch, yogurt as a snack, and a dish containing legumes or tofu for dinner.

Your protein needs should be determined individually, taking into account your kidney function, digestion and your specialist's recommendations. If ordinary food is not enough, discuss specialized nutritional drinks with your doctor.

3. Increase the Calorie Content of Your Usual Meals

When you feel full quickly, simply increasing portion sizes does not always help. It is more practical to make smaller amounts of food more nutritious. You can do this in several simple ways:

• Porridge: Add butter, milk or milk powder if you tolerate these foods well.
• Mashed potatoes: Enrich them with milk and butter.
• Cream soups: Add suitable dairy products or a little oil.
• Cottage cheese and yogurt: Combine them with nuts or other calorie-rich ingredients that you can tolerate.
• Vegetable dishes: Use vegetable oil to increase the energy content of each portion.
• Smoothies and shakes: Prepare nutritious milk-based drinks with yogurt, cottage cheese or other suitable ingredients.

This approach helps you get more energy without forcing yourself to eat significantly larger portions.

4. Choose Food Textures That Suit How You Feel

If chewing or swallowing is painful, do not force yourself to eat dry, hard foods. During these periods, smooth soups, soft porridge, cottage cheese, yogurt and other foods with a suitable texture may be easier to manage.

If ordinary food makes you feel sick, you can discuss liquid options with your doctor, such as nutritional drinks, smoothies, milkshakes and soups. These may be more convenient on days when eating a full meal is difficult.

If you have soreness in your mouth or throat, difficulty swallowing or persistent vomiting, simply changing your menu is not enough. You need to inform your medical team about these symptoms so they can identify the cause and provide appropriate support.

5. Maintain Proper Hydration

Not drinking enough fluids can make you feel even worse, especially if you are experiencing vomiting or diarrhea. If you have no individual fluid restrictions, spread permitted drinks into small portions throughout the day.

You can take small sips of water between meals rather than trying to drink a large amount at once. If drinking makes your stomach feel overly full, discuss a more comfortable schedule with your doctor.

There is no universal daily fluid requirement for all cancer patients. Some accompanying conditions require fluid restriction, so you should follow your treating specialist's recommendations.

6. Do Not Try to Lose Weight or Impose Strict Restrictions

During treatment, you should not switch to fasting, detox programs or eliminate entire food groups on your own in an attempt to cleanse your body. Such restrictions can further reduce your intake of energy and nutrients.

If your appetite has decreased, the goal is not to make your diet as restrictive as possible, but to maintain adequate nutrition while taking food tolerance into account. If your weight continues to drop despite dietary changes, you need to consult your oncologist and a clinical nutrition specialist.

My Advice: What I Have Observed About Supporting the Body

First. I recommend paying special attention to nutrition when you feel weak. In my books, I describe freshly squeezed vegetable juices as an additional source of nourishment for people experiencing fatigue and nervous exhaustion. I mention combinations of carrots, celery, parsley, spinach and lettuce. In my view, these juices require very little digestive effort and can help support the body when appetite is poor and ordinary food is difficult to manage. I associate their effects with nourishing the nervous system and blood. However, with cancer, food safety is important: medical specialists do not consider juices a complete substitute for nutritious meals, and when immunity is reduced, they recommend avoiding unpasteurized juices.

Second. I believe it is especially important not to overload your diet with complicated food combinations when you are ill. In *The ABCs of Health*, I write that different foods require different amounts of time and conditions for digestion. According to my approach, when food is too complicated and the body has to use a lot of energy to process it, that energy is diverted from other tasks. That is why I favor simple, straightforward meals and paying close attention to what goes into your diet. However, there is an important consideration when it comes to cancer-related weight loss: medicine prioritizes providing enough calories and protein, even if this means choosing more nutritious and varied meals.

Third. I believe maintaining strength depends on the functioning of the entire body. In my chapter on cancer, I emphasize the importance of nutrition, blood, lymph and circulation. In my view, we cannot treat the body as a collection of separate organs: illness affects the person as a whole. That is why I recommend conserving your energy, alternating activity with rest and avoiding nervous exhaustion. At the same time, modern oncologists assess muscle loss separately and recommend choosing physical activity according to the patient's condition.

Fourth. I believe we should not expect immediate changes. In my books, I remind readers that the body needs time to regain its balance. With cancer, I would particularly emphasize the importance of being patient with yourself: do not blame yourself for a reduced appetite, weakness or changes in weight. My approach to supporting the body should never become an additional source of restrictions. If your weight continues to fall, you need to tell your treating oncologist and work together to find a way to preserve your nutrition and strength.

What Foods and Remedies Should You Avoid During Chemotherapy Without Your Doctor's Approval?

During anticancer treatment, even familiar foods and herbal remedies require careful consideration. Some substances can change how medications work, so you should not experiment with supplements or concentrated extracts on your own.

Be particularly careful with the following foods and remedies:

• St. John's wort. It can affect the concentration of certain anticancer medications and change how they work. Do not take it as an infusion, medicinal-strength tea or supplement without consulting your oncologist.
• Grapefruit and grapefruit juice. They can affect the metabolism of certain medications and the concentration of active substances in your body. Avoid them during treatment until your doctor gives you permission.
• High doses of antioxidants. Taking them during chemotherapy or radiation therapy without your doctor's approval is not advisable. This primarily concerns concentrated supplements, not ordinary portions of vegetables and fruit.
• Concentrated herbal extracts. Even if a plant seems harmless, a concentrated product can interact with medications. Do not start taking such products on your own.

This does not mean that patients must avoid all plant-based foods. Ordinary vegetables and fruit do not need to be automatically excluded from your diet. What matters is the quantity, form of consumption, individual tolerance and possible interactions.

Before using any herb or supplement or making changes to your diet, talk to your oncologist. Do not stop prescribed medications or replace them with products from naturopathic programs.

When to See a Doctor

When you have cancer, it is important to distinguish between situations requiring immediate medical attention and symptoms that should be discussed at your next appointment.

When to Seek Urgent Medical Attention

The following symptoms require immediate medical assessment:

• A temperature of 38 °C or higher, or chills during chemotherapy. Contact your oncologist immediately. Do not try to bring down the fever on your own and wait for improvement: during chemotherapy, a fever can be a sign of a serious complication.
• Shortness of breath, chest pain or swelling in one leg. Do not delay seeking medical help, especially if these symptoms appear suddenly.
• Vomiting for more than a day or being unable to drink. This creates a risk of dehydration and requires urgent assessment.
• Blood in your stool or vomit, or black stools. These signs should not be dismissed as mere treatment side effects or dietary changes.
• Fainting or a rapid heartbeat. These are particularly dangerous if accompanied by severe weakness, dizziness or a worsening general condition.

If you experience chest pain, severe shortness of breath, fainting or another acute condition, call emergency services. Do not wait for your next scheduled clinic appointment or try to determine the cause of the symptoms yourself.

When You Should Make a Routine Appointment

Do not put off discussing the following changes with your doctor:

• Unexplained weight loss has started.
• Your appetite has decreased significantly, and your usual diet is no longer providing enough nutrition.
• You have persistent nausea, diarrhea or constipation.
• You are having difficulty chewing, swallowing or keeping food down.
• You feel unusually full after eating only a small amount.
• Your muscle strength is decreasing, and familiar activities are becoming more difficult.
• You are experiencing pain, anxiety or low mood that interferes with normal eating.

It is particularly important to tell your doctor about any changes in weight, even if they seem minor. You do not need to wait until you become severely malnourished to ask for help.

During your consultation, discuss your diet, possible treatment side effects and whether you need support from a clinical nutrition specialist. Sometimes changing your menu is not enough, and additional nutritional support may be necessary.

You can learn more about how I approach this subject on the page "Oncology".

Boris Wydoff — naturopath and author, Ph.D. in nutrition. For over fifty years I have helped people restore health through nutrition, cleansing and the power of the mind — in Europe, America and Asia. About the author →

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