Metabolic approaches to cancer: questions to ask your oncologist

CANCER SUPPORT · 8 MIN READ

Keto, fasting and metabolic protocols are everywhere online. Before you change how you eat during treatment, these are the questions worth bringing to your oncology team.

Summary

• There is no single cancer diet. What suits you depends on your treatment, your weight, your muscle and how you are coping.

• Restrictive diets and fasting can harm people who are losing weight or muscle.

• Bring any planned change in eating to your oncology team first.

Metabolic approaches to cancer have become one of the most searched topics in cancer care. Ketogenic diets, fasting, fasting-mimicking diets and metabolic protocols are discussed in books, podcasts and online groups, often with great confidence.

The research is still developing, and there is no single cancer diet. What matters most is how any change in eating affects you, the person going through treatment: your weight, your muscle, your blood sugar, your energy and your ability to complete treatment well.

What does metabolic health mean during treatment?

Metabolic health is how well your body manages energy: blood sugar, insulin, muscle and body fat. During treatment, it shapes how you cope. People who keep their muscle and steady their blood sugar often manage treatment better, whatever their diagnosis.

That is why the questions below are about you, not about the diet.

Why the same diet can suit one person and not another

A ketogenic diet or fasting might be considered, with medical supervision, for someone who is carrying extra weight and has stable muscle mass. For someone who is already losing weight or muscle, the same approach can make things worse. International clinical nutrition guidelines advise against restricting energy in people at risk of malnutrition during cancer treatment.

Your needs can also change during treatment. What suited you before surgery may not suit you during chemotherapy, and what suits you in a good week may not suit you in a hard one.

Questions to ask your oncologist

• Is there any reason a change in how I eat could affect my treatment?

• Am I at risk of losing weight or muscle, and how will we measure that?

• Does my treatment affect my blood sugar? Am I on steroids?

• Would you support me trying a lower-carbohydrate or time-restricted way of eating, and what would you want monitored?

• Should I avoid fasting before or after treatment days?

• Can I see an exercise physiologist on the team?

• What signs would mean I should stop and come back to you?

What tends to suit most people during treatment

• Enough protein at every meal, to protect muscle

• Steady blood sugar: no refined sugar, and carbohydrates from whole foods

• Regular meals rather than long gaps, unless your team advises otherwise

• Movement your team agrees with, including gentle strength work

• Regular checks of weight, muscle and energy, not just the scales

Principles, not rules

Dogmatic eating has little place during treatment. Principle-centred eating does: protect muscle, steady blood sugar, choose clean whole food, and adapt as your body and your treatment change.

How I work alongside your oncology team

I look at your weight, muscle, blood sugar, appetite and energy, and match food to you and your treatment stage. Plans are principle-centred and adapt as your treatment changes.

Any change is shared with your oncology team in writing before you begin.

Frequently asked questions

Is a ketogenic diet safe during chemotherapy? It depends on the person. For anyone losing weight or muscle, restrictive diets can make things worse. Ask your oncology team before starting.

Should I fast before chemotherapy? Fasting around treatment is still being researched and is not suitable for everyone, especially if you are losing weight. Check with your oncologist first.

What is the best diet during cancer treatment? Most people do well with enough protein, steady blood sugar, whole foods and regular meals. The details depend on your treatment and how you are coping.

Where to start

If you are weighing up a change in how you eat during treatment, an initial consultation is a place to think it through: your weight, muscle, blood sugar and treatment plan, and the questions for your team. Consultations are online, consult by consult.

This article is general education. In consultation, everything is coordinated with your oncology team.