Cancer’s Fuel Source: Why Cutting Carbs Could Save Your Life

What if one of the most promising cancer treatments doesn’t come from a pharmaceutical lab, but from understanding how cancer cells eat?

This isn’t about replacing conventional cancer treatment. It’s about understanding a biological mechanism that could make treatments more effective while potentially extending and improving patients’ lives.

The Metabolic Theory of Cancer

For decades, the medical establishment has treated cancer as primarily a genetic disease: random mutations cause cells to go rogue. But Professor Thomas Seyfried, a biologist who has dedicated 30 years to cancer research, presents compelling evidence for a different view: cancer is fundamentally a metabolic disorder.

“Cancer is getting worse, and there’s no major advance in reducing death rates,” Dr. Seyfried explains. “All major cancer research centers think cancer is a genetic disease. It’s not whether you believe, it’s what the data tell us, and the evidence is massive to support that cancer is a metabolic disorder.”[^1]

The key insight comes from Otto Warburg, who won the Nobel Prize in 1931 for discovering that cancer cells have a damaged ability to produce energy efficiently. Unlike normal cells, which primarily use oxygen to burn fuel in their mitochondria (the cell’s power plants), cancer cells rely on an ancient, inefficient process called fermentation. They can only use two specific fuels: glucose (sugar) and glutamine (an amino acid).

This isn’t a minor detail. It’s a fundamental vulnerability that can be exploited.

How Keto and Fasting Target Cancer Cells

Here’s where the metabolic approach becomes revolutionary: when you drastically reduce carbohydrates (through a ketogenic diet) or stop eating entirely (through fasting), something remarkable happens.

Your body runs out of glucose. In response, your liver begins breaking down fat and producing small molecules called ketones. These ketones become an alternative fuel source that can power your brain, heart, kidneys, and every other organ.

But here’s the critical difference: normal cells can use ketones efficiently. Cancer cells, with their damaged mitochondria, cannot.

As Dr. Mark Hyman explains: “Cancer has a metabolic capacity to only burn carbs. It can’t burn fat. So if you stop carbs and you eat fat, you can often change the trajectory of cancer.”[^2]

By transitioning your body into nutritional ketosis (through diet or fasting), you selectively starve cancer cells while continuing to fuel your healthy cells. The cancer cells, deprived of their preferred fuels, slowly weaken and die. Meanwhile, your immune system and healthy tissues remain well-nourished.

Real Cases: When Theory Becomes Life-Saving Reality

Dr. Boz’s Mother: A 70% Reduction in Six Weeks

Perhaps no story illustrates this approach more powerfully than Dr. Annette Bosworth’s (Dr. Boz) personal experience with her own mother.

In 2015, her mother walked into her office looking “gray” and “like a zombie.” Cancer had returned for the third time. Large lymph nodes bulged in her neck. The oncologist recommended immediate chemotherapy.

But her mother refused. She remembered what chemotherapy had done to her mind during previous treatments: “I didn’t know what a sewing machine was,” she said, referring to an activity she had loved her entire life.

The prognosis without treatment: six months to live.

Standing in the hospital waiting room, her mother asked the question that would change everything: “If it was you, what would you do?”

Dr. Boz had been researching ketogenic diets for brain injuries and cancer. She made a bold decision. They walked out of the hospital together, drove 100 miles to the family farm, and threw out every carbohydrate in the house.

Six weeks later, the results stunned even her oncologist friend:

Expected reduction with chemotherapy: 30%
Actual reduction with ketogenic diet: 70%

“He walks in, and he slides the piece of paper over to me and says, ‘How did you get her numbers to drop by 70%? There’s no drug on the market that would do that,’” Dr. Boz recalls.[^3]

Her mother transformed from looking like a dying 100-year-old to a vibrant woman who looked 40. She lived years beyond her prognosis, returning to her active life volunteering and serving her small community.

“When you put them in a ketogenic state, it really helped her cancer. It really did that Warburg effect,” Dr. Boz explains. “She was a new human within three weeks.”[^3]

Water Fasting and Lymphoma: 10+ Years Cancer-Free

Dr. Alan Goldhammer, who has supervised thousands of extended water fasts at True North Health Center, published remarkable cases in the British Medical Journal.

Case 1: Follicular Lymphoma

A young woman with follicular lymphoma had watched her disease progress for two years. Her oncologist told her diet didn’t matter and she could “eat whatever she wanted.”

She decided differently. She came to True North Health and completed a 21-day water fast.

“You could literally feel these tumors disappearing,” Dr. Goldhammer reports.

When she returned for her one-year follow-up CT scan, the initial results seemed too good to believe. The British Medical Journal asked them to follow her for three years to rule out spontaneous remission (which occasionally happens with lymphoma).

Three years later: cancer-free.

Ten years later: still cancer-free.[^4]

The key? After the fast, she maintained a whole-food, plant-based diet free of salt, oil, and sugar, sustaining the metabolic environment that kept cancer at bay.

Case 2: Stage 4 Lymphoma with Bone Metastasis

Another patient arrived with even more aggressive disease: stage 4 lymphoma that had spread to his bones. He had already failed chemotherapy.

His oncologist was “quite antagonistic” about fasting, worried it would make him too weak for treatment. But after a three-week fast, the oncologist changed his tune: “Wow, that’s really impressive. Why don’t you go back and do some more of that?”

The patient returned and completed a 39-day water fast. He achieved significant remission and has maintained it through dietary management.[^4]

Pablo: Refusing Standard Treatment

Dr. Seyfried references a patient he worked with named Pablo who had aggressive cancer. Instead of accepting radiation and chemotherapy, Pablo chose metabolic therapy.

“He didn’t take radiation or chemo. And he brought his glucose ketone index down to the 2.0 zone and kept it low,” Dr. Seyfried explains.[^1]

The glucose ketone index (GKI) is a measurement that divides your blood glucose level by your blood ketone level. A GKI of 2.0 or below indicates deep therapeutic ketosis, the zone where cancer cells are maximally stressed while healthy cells thrive.

Pablo supplemented this with non-toxic strategies and has outlived his prognosis by years.

The Science: How It Works

The Warburg Effect

In the 1920s, Otto Warburg discovered that cancer cells have fundamentally different metabolism than healthy cells. Even when oxygen is available, cancer cells preferentially use fermentation (energy production without oxygen) rather than oxidative phosphorylation (the efficient oxygen-using process in mitochondria).

This shift happens because of chronic damage to the mitochondria, the cell’s powerhouses. That damage doesn’t occur overnight; it’s a gradual process driven by:

Processed foods and excess carbohydrates
Lack of exercise
Chronic inflammation
Oxidative stress
Environmental toxins
Chronic emotional stress
Poor sleep

“Cancer is very preventable,” Dr. Seyfried emphasizes. “The problem is we’re doing everything we possibly can in our lifestyle to induce it.”[^1]

Selective Metabolic Stress

The beauty of metabolic therapy is its selectivity. Dr. Seyfried explains the mechanism:

“A solution to the cancer problem, to manage cancer without toxicity, is to simultaneously restrict the two fuels that are needed to drive this dysregulated growth [glucose and glutamine] while transitioning the whole body off to a fuel that the tumor cells can’t use, which is fatty acids and ketone bodies.”[^1]

When you enter nutritional ketosis through fasting or a ketogenic diet:

Blood sugar drops dramatically, removing cancer’s primary fuel
The liver produces ketones from stored body fat
Normal cells switch to burning ketones, which they handle efficiently
Cancer cells cannot effectively use ketones due to damaged mitochondria
Cancer cells are selectively weakened and become vulnerable to elimination

Enhanced Treatment Effectiveness

Here’s what makes this approach even more promising: metabolic therapy doesn’t just work on its own. It can dramatically enhance conventional treatments.

Dr. Seyfried’s colleagues in Istanbul, Turkey, have shown that “when you are in nutritional ketosis with a glucose ketone index of 2.0 or below, chemotherapies at much lower dosages can be even more therapeutically powerful.”[^1]

This means patients might achieve better results with fewer side effects by combining metabolic therapy with reduced-dose conventional treatments.

The Evidence from Our Evolutionary Past

If cancer were truly random genetic bad luck, we’d expect to see it throughout nature and human history. But we don’t.

In Traditional Societies:

Albert Schweitzer, the renowned humanitarian physician, noted something remarkable when he went to Africa: cancer was extremely rare in tribes living according to traditional ways. But when modern diet and lifestyle entered their societies, “cancer had a control.”[^1]

Similar observations were made of people living in the Arctic Circle and Aboriginal populations. Cancer was conspicuously absent.

In Our Primate Relatives:

“There’s never been a documented case of breast cancer in a female chimpanzee,” Dr. Seyfried notes. “And they’re 98% similar to us in gene and protein sequence.”[^1]

In Modern Examples:

We even see this in domesticated animals. Wolves in the wild don’t die from cancer. But cancer is the number one killer of domestic dogs. The difference? Diet and lifestyle.

For hundreds of thousands of years, our ancestors existed in a state of nutritional ketosis. Carbohydrates were scarce. Our species evolved burning primarily fat and ketones for fuel. Cancer was rare.

We didn’t evolve to eat “pork pies and Dunkin Donuts, jelly-filled donuts and pizzas,” as Dr. Seyfried colorfully puts it. “Our food science and technology and our society’s technology has evolved so much faster than our biology.”[^1]

Practical Implementation: The Keto Continuum

If you or a loved one is facing cancer, how do you actually implement metabolic therapy? Dr. Boz has developed a systematic approach she calls the “Keto Continuum”: a 12-step process for achieving and maintaining therapeutic ketosis.

The Basics

For a standard ketogenic diet:

Very low carbohydrates: Under 20-50 grams per day (typically 20-30 grams)
High healthy fats: About 70% of calories
Moderate protein: About 20-25% of calories

The goal: Consistently produce measurable ketones in your blood (at least 1.0 mmol/L, ideally higher for therapeutic purposes).

Time-Restricted Eating

As your body adapts, you progress to eating within narrower time windows:

16:8 (eating within 8 hours, fasting for 16)
23:1 (one meal per day)
Gradually shifting meal timing earlier in the day

Extended Fasting

For more aggressive metabolic intervention (especially for those with high insulin resistance or active cancer):

36-hour fasts
72-hour fasts
Multi-week water fasts (under medical supervision)

Dr. Goldhammer notes that the lymphoma patients who achieved remission typically needed 21 days or more of water fasting, followed by strict dietary adherence.[^4]

Measuring Success

Don’t guess; measure. Use blood ketone and glucose meters to calculate your Glucose Ketone Index (GKI):

GKI = Blood Glucose (mg/dL) ÷ 18 ÷ Blood Ketones (mmol/L)

For therapeutic purposes (cancer, serious neurological conditions):

Target GKI: 2.0 or below
Moderate ketosis: 3.0-6.0
Light ketosis: 6.0-9.0

Supporting Tools

Exogenous Ketones: For cancer patients who need high ketone levels quickly (such as before chemotherapy), supplemental ketones can help. Dr. Boz uses them for patients who “can’t afford to fast for 48 hours. They don’t have the time.”[^3]

Exogenous ketones:

Raise blood ketone levels within 15-20 minutes
Signal the liver to produce more ketones for the next 12 hours
Provide antioxidants for protection during chemotherapy or radiation
Help preserve muscle mass during treatment

Important Considerations and Cautions

This Is Not Medical Advice

Critical point: Metabolic therapy for cancer should be undertaken only with medical supervision, preferably with physicians experienced in this approach.

Dr. Boz is careful to note: “When I look at patients now who say, am I going to reverse my cancer with a ketogenic diet? I’m like, no, but you are going to deal with it a lot better.”[^3]

Individual Variation

What works for one person may not work identically for another. Factors that influence response include:

Type and stage of cancer
Metabolic health baseline
Genetic factors
Stress levels
Sleep quality
Activity levels

Potential Risks

Extended fasting and extreme carbohydrate restriction can be risky if they lead to:

Malnutrition
Excessive fatigue
Reduced treatment tolerance
Electrolyte imbalances

Professional monitoring of blood work, electrolytes, and overall health is essential.

Integration with Conventional Treatment

Most experts don’t advocate abandoning conventional cancer treatment entirely. Instead, they see metabolic therapy as:

A complementary approach that can enhance treatment effectiveness
A way to potentially reduce the doses (and side effects) of conventional treatments
A means of improving quality of life during treatment
A preventive strategy before and after active treatment

Beyond Cancer: The Broader Health Benefits

What makes metabolic therapy particularly compelling is that it doesn’t just target cancer. The same approaches that starve cancer cells also:

Reduce inflammation throughout the body: Even low-level chronic inflammation impairs healing and promotes disease. Ketogenic diets and fasting dramatically lower inflammatory markers.

Lower oxidative stress: This cellular damage accumulates from everyday life, stress, poor sleep, and environmental toxins. Reducing it enhances the body’s ability to repair and regenerate.

Reverse insulin resistance: High insulin levels not only fuel cancer growth but also drive obesity, diabetes, heart disease, and cognitive decline.

Improve cognitive function: The brain runs beautifully on ketones. Many people report enhanced mental clarity, focus, and mood stability in ketosis.

Preserve muscle mass: Unlike caloric restriction alone, ketogenic approaches (especially when protein is adequate) tend to preserve lean muscle while burning fat.

The Bigger Picture: Prevention

While these stories focus on cancer treatment, perhaps the most powerful application is prevention.

Dr. Seyfried puts it bluntly: “If you do metabolic therapy, you can actually reduce risk for cancer. You can take away the fear.”[^1]

Consider that:

Cancer develops gradually over years or decades
It requires chronic damage to cellular metabolism
That damage is largely driven by lifestyle factors we control

Every time you fast, every day you maintain nutritional ketosis, you’re:

Giving your mitochondria a break from constant fuel processing
Triggering cellular cleanup processes (autophagy)
Reducing the metabolic conditions that allow cancer cells to thrive
Training your body to efficiently use fat and ketones

The Path Forward

The evidence for metabolic approaches to cancer is growing, but it remains on the fringes of mainstream oncology. Dr. Seyfried notes with frustration: “Most of the poor oncologists never heard of what I’m talking. The stuff I’m telling you right now, they never heard of it.”[^1]

Why the resistance? Multiple factors:

Medical training focuses almost entirely on pharmaceutical and surgical interventions
The cancer industry is built around conventional treatments
Dietary interventions can’t be patented
The evidence, while growing, hasn’t yet reached the level of large randomized controlled trials (which require massive funding)

But the individual cases are impossible to ignore. When a 70% reduction in cancer markers happens in six weeks. When stage 4 lymphoma goes into remission with fasting. When patients outlive dire prognoses by years.

As Dr. Seyfried says: “If I had a drug that did what metabolic therapy did, are you kidding me? They’d be running all over the world.”[^1]

Taking Action

If you or someone you love is facing cancer:

Educate yourself thoroughly on metabolic approaches
Find knowledgeable medical support: Seek physicians experienced in metabolic therapy (they exist, though they’re not yet common)
Measure, don’t guess: Use blood testing to track glucose, ketones, and your GKI
Start where you are: Even modest carbohydrate reduction and intermittent fasting can begin shifting your metabolism
Prioritize overall metabolic health: Exercise, sleep, stress management, and community all matter
Be patient: Metabolic shifts take time; Dr. Boz notes her mother “was a new human within three weeks” but “this was a year and a half before she got to be the best version of herself”[^3]

For prevention:

Regular fasting: Even time-restricted eating (16:8) provides benefits
Periodic deeper fasts: Consider 24-72 hour fasts several times per year
Reduce processed carbohydrates: Even if you don’t go full keto, minimize sugar and refined carbs
Exercise regularly: It lowers both glucose and glutamine, the two fuels cancer needs
Build metabolic flexibility: Train your body to efficiently switch between glucose and fat burning

Conclusion: A Fundamentally Different Approach

The metabolic theory of cancer offers something conventional approaches often lack: a clear biological mechanism that explains both prevention and treatment.

Cancer cells aren’t mysterious entities with infinite adaptive capacity. They’re cells with damaged metabolism, dependent on specific fuels, operating in the body’s metabolic environment.

Change that environment, and you change their ability to survive.

The stories of Dr. Boz’s mother, the lymphoma patients at True North Health, and countless others suggest we may have been overlooking one of nature’s most powerful anti-cancer interventions.

As Dr. Seyfried concludes: “When they come to know what I know about this disorder, and then they realize what we’ve been doing in a misdirected way, it’ll be recognized as the greatest tragedy in the history of medicine.”[^1]

But knowledge creates opportunity. If metabolic dysfunction creates cancer, then metabolic health can prevent and potentially treat it.

The power may have been on your plate all along.

References

[^1]: The Groundbreaking Cancer Expert: This Common Food Is Making Cancer Worse – Dr. Thomas Seyfried on The Diary Of A CEO with Steven Bartlett

[^2]: How to Improve Your Vitality & Heal From Disease – Dr. Mark Hyman on Huberman Lab

[^3]: Insulin Doctor: This Is The First Sign Of Dementia – Dr. Annette Bosworth on The Diary Of A CEO with Steven Bartlett

[^4]: Water Fasting Scientist: Surprising Link Between Fasting & Cancer – Dr. Alan Goldhammer on The Diary Of A CEO with Steven Bartlett

[^5]: Tim Ferriss: 4 Science-Backed Tools That Rewired Decades of Childhood Trauma – Tim Ferriss on The Diary Of A CEO with Steven Bartlett