The ketogenic, or keto, diet has gained fame for its rapid weight-loss promise and supposed metabolic edge. Built around high fat, very low carbohydrates, and moderate protein, it aims to switch the body’s fuel source from glucose to fat, a state called ketosis.
But what happens when the same logic is applied to something as complex as cancer? Can cutting carbs actually “starve” tumours, or could it, in some cases, end up feeding them instead? According to Dr Bhavisha Ghugare, Senior Consultant, Surgical Breast Oncology at HCG Cancer Centre, Borivali, it’s time to separate the hype from the human biology.
What keto claims and what science says
The keto diet’s popularity in cancer discussions comes from a simple theory: since most cancer cells rely heavily on glucose, depriving them of sugar might slow their growth. “While this theory sounds logical, breast cancer is not a single disease,” Dr Ghugare explains. “It has many subtypes, each behaving differently. At present, there is not enough scientific evidence to say that the keto diet is beneficial or harmful in treating breast cancer.”
In short, what might work in lab models doesn’t necessarily translate safely or effectively to real-world patients.
When fat becomes fuel for cancer cells
Emerging research now suggests that some aggressive breast cancers can, in fact, use fat, or ketones, as an alternative energy source. In such cases, a high-fat, low-carb diet could do the opposite of what’s intended.
“These cancer cells adapt quickly,” says Dr Ghugare. “Instead of starving, they can thrive on ketones, the very molecules a keto diet increases. This shows why a single diet can’t suit all cancer types — the biology is far too complex.”
The takeaway? What fuels healing in one situation might quietly feed disease in another.
Why drastic diet changes can be risky during treatment
Cancer treatment already puts enormous strain on the body, altering hormones, metabolism, and liver function. Adding an extreme diet can worsen that burden.
“Very high-fat diets can raise cholesterol and affect liver health,” Dr Ghugare cautions. “Meanwhile, cutting out whole food groups — fruits, grains, and legumes — can lead to nutrient deficiencies and increased inflammation.”
Since many breast cancer therapies already increase cardiovascular risks, diets that spike inflammation or disrupt balance may do more harm than good.
Finding balance: the healthy side of low-carb living
Not every aspect of carbohydrate restriction is unhealthy. Avoiding refined sugar and processed foods is undeniably beneficial. Replacing them with whole foods and healthy fats — nuts, seeds, olive oil, and avocados — can support healing and hormone balance.
“The goal should never be strict restriction,” says Dr Ghugare. “The goal is nourishment, food that supports treatment, recovery, and long-term health.”
There is no single ‘anti-cancer’ diet
What truly helps, experts agree, is variety. A balanced plate, colourful vegetables, seasonal fruit, whole grains, lean protein, and moderate healthy fats, provides the antioxidants, fibre, and energy the body needs to recover and resist recurrence.
Before adopting any major dietary change, especially one as restrictive as keto, it’s vital to consult an oncologist or clinical nutritionist familiar with your treatment plan. “Every patient’s body and tumour behaves differently,” Dr Ghugare reminds. “Your diet should help your therapy, not compete with it.”
The keto diet may be fashionable, but when it comes to breast cancer, food isn’t just fuel; it’s chemistry. What helps one person may harm another. The safest path forward? Science, supervision, and moderation. Dr Ghugare sums up, “Healing isn’t about extremes. It’s about giving your body what it truly needs, not what’s trending.”
Also read: Breast cancer cases rising among young women: Expert explains causes and concern
