Prof Stephen Phinney – The Art and Science of Low-Carb Living at The Old Mutual Health Convention

We are facing an epidemic of obesity and diabetes globally. If we don’t resolve it, it will bankrupt us.

One way is with a ketogenic diet that is low-carb, high-fat, moderate protein.

My research has been into ketogenic diets for improved athletic performance, but the principles are the same for non-athletes, for weight loss and treatment of diseases such as obesity, diabetes or pre-diabetes (insulin resistance).

When you restrict protein to moderate in the diet, and eat very little carb, your body turns some of the fat you eat or have stored into chemicals called ketones.

Ketones have a bad name among doctors and dietitians, because we were taught that when ketones get really high, they could turn into ketoacidosis that can kill. That only happens when your body can’t make insulin as in Type 1 diabetes.

Type 2 diabetes doesn’t go into ketoacidosis, because even if you have a little insulin in your body, you won’t go into ketoacidosis. If you eat protein in moderation and keep carbs low (under 50g) your ketones will stay in the range between 1 and 3 millimolas – what we call nutritional ketosis. It is safe, not dangerous at all, as some people still think.

If you eat too many carbs, you go into what we call the carbage zone – when the carbs in the body suppress your body’s ability to utilize fat for fuel.

The nutritional ketosis range is where ketones act as a sustaining fuel for the body. Instead of using blood sugar for fuel, if you take away the carbs over a course of a few weeks, once you get into that adapted state, ketones become your source of fuel. It involves four phases – adapt, adjust, build, maintain.

The true experts in a properly formulated ketogenic diet are Inuit women. We don’t know precisely what they ate, but Dr Frederick Schwatke, an American medical doctor and explorer, tried to find out. He made an expedition to the arctic for two years from 1878 to 1880, and made this observation:

“When first thrown wholly upon a diet of reindeer meat, it seems inadequate to properly nourish the system, and there is an apparent weakness and inability to perform severe exertive fatiguing journeys. But this soon passes away in the course of two or three weeks.”

This observation was written a century before “keto-adaptation” or “fat adaptation” was known. Schwatke was the first experiment in human keto-adaptation. It showed that you can’t make transition from high carb to low overnight. Most of the studies done comparing low-carb high-fat diets have less than 2-week duration.

After Schwatke, Harvard-trained anthropologist Vilhjalmur Stefansson went to the Arctic to study the Inuit language and culture with a group of Inuit on the Canadian Arctic coast

Stefansson wrote extensively about these experiences in both scientific literature and in books for the lay public. A main theme of his writing was the adaptation of the Inuit culture to survive as nomadic groups in the arctic on a diet of the products of hunting and fishing.

His claim that you could live and function well on products of just one food group caused controversy. He so scandalised the nascent nutrition establishment at the time that he agreed to be locked up in a hospital for a year by doctors who put him on a diet of meat and fat expecting him to very sick, and possibly even die. They expected him to get scurvy. He didn’t.

This was known as the 1928 Bellevue Stefansson Experiment. Data were written up and in it, and it was stated that the experiment failed. It would be unethical to do something like that today.

The experiment shows principles of low-carb eating in the Inuit diet:

  • A low-carb diet as eaten by aboriginal is not high protein. It is moderate protein and high fat: 80% of calories came from fat.
  • The Inuit eat meat frozen or raw. They boiled and drank the broth. That is an important point.
  • They eat animals ‘nose to tail’: liver, kidneys, the bone marrow which is rich in fat, great source of iron.

That kind of traditional diet is very different from what official dietary guidelines advise today.

I came to the question of keto diets for athletes as a young scientist in the late 197os, early 1980s. I thought I had found something original, although Schwatke scooped me by 100 years.

My research aimed at preventing athletes from “hitting the wall”. An athlete hitting the wall is like a gasoline tanker running out of diesel fuel on the highway. It is common among endurance athletes.

The current consensus still is that a high carbohydrate diet is necessary for competitive endurance sports performance. My research has shown that it isn’t.

There is some scientific support for “carbohydrate loading” to enhance sports performance. But all studies showing benefits of high carb over low carb involved adaptation periods of less than 14 days. Some of these studies involved very high protein intakes (>300 grams per day). None purposefully supplemented minerals

Studies show that even in a very lean athlete (10-15% body fat), the body still has more than 50,000 kcal of fat reserves plus 20-30,000 kcal protein when hitting the wall happens. Therefore hitting the wall represents a failure of inter-organ fuel partitioning, not a lack of fuel.

My research has involved looking at optimal fuel flow for brain and muscles.

My point of entry into the research was my own personal experience of riding my bicycle during medical training.

It has been thought that if endurance athletes went on an Atkins type diet it would impair their performance. My research shows this is not the case. It adds new evidence that if you eat saturated in healthy diet, and eliminate sugar and refined carbs, it’s definitely not dangerous.

I started studying ketogenic diets for athletes using the ketone zone – from nutritional ketosis to post-exercise ketosis.

We designed the Keto-adaptation Demonstrated Vermont study, published in 1980.

  • 6 subjects were “locked up” for 7 weeks
  • After a week of baseline studies, all subjects ate a meat/fish/poultry supplemented fast (~600 kcal/d) with supplemental minerals and vitamins
  • Endurance performance was assessed at baseline, 1 week, and 6 weeks of the ketogenic diet
  • At 6 weeks, each individual’s weight loss was compensated by a backpack loaded to recreate their starting weight.

The study showed that given 90 grams per day of protein as meat, adequate salt and potassium, trace minerals and vitamins, obese humans adapt to recover full endurance performance within 6 weeksIt appeared to validate an Atkins diet for endurance, but there were variables that needed to be investigated.

Rather than have people lose weight during the experiment, we looked at highly trained athletes who know what exhaustion feels like.

In 1983, the Keto-adaptation Confirmed MIT Study verified the “Vermont Study” result for a full-calorie (eucaloric) ketogenic diet given to 5 highly fit and lean bicycle racers. Key management factors were protein content, type of dietary fat, major & trace minerals:

  • 4 weeks of adaptation was allowed between baseline and final endurance tests
  • Diet composition was patterned after Stefansson
    • 15% protein
    • 80+% fat
    • < 2% carbohydrate

Among the findings was that there was no change in peak aerobic power endurance time to exhaustion. Although having half as much glycogen before exercise, these athletes used it only one fourth as fast once keto-adapted.

Our interpretation of the data was that keto-adaptation is associated with a dramatic shift in whole-body fuel use during exercise. Despite 90% of calories coming from fat, their bodies had become skilled at preserving glycogen. It was a remarkable change in fuel use.

We published the data, and we sat there. You can have data in sight for years, but if no one wants to see it, it just sits there.

I have been considered a heretic for my views on low-carb, high-fat diets. I became so frustrated trying to get the message out that this is not dangerous, that eventually, I dropped out of academia. I call myself a recovering academic.

Later, I met Dr Jeff Volek, who took my data and said we should look at it from the perspective of current literature.

Although a critical mass of experimental data on ketogenic diets and ketone physiology has been generated in the last decade demonstrating safety and therapeutic efficacy in managing a range of clinical conditions, there has been little effort focused on studying the keto-adapted athlete.

However, the long-standing dogma that carbohydrates are not only preferred but an essential fuel for athletes is collapsing under the weight of empirical evidence from pioneering athletes who have abandoned carb-dense foods in favor of a low-carbohydrate, high-fat, moderate-protein diet.

These ‘keto-adapted’ athletes aren’t just finishing races; some are winning & setting records.

We’ve also written studies with Prof Tim Noakes on pioneering athletes who have adopted low-carb, high fat as a lifestyle. One is Tim Olsen, who in 2012 won the Western States 100 mile Endurance Run in his best time. Critics said it was a once-off. Tim Olsen went back the next year and won the race again.

In 2013 we designed the FASTER study to characterize the metabolic and physiologic differences between high-calibre runners habitually consuming a very low-carbohydrate diet (LCD) versus a traditional high-carbohydrate diet (HCD).

It showed that keto-adapted athletes are phenomenal fat burners. It also showed remarkable rates of fat oxidation.

There is also growing research to show the positive effects of ketogenic diets in people with metabolic syndrome in reducing cardiovascular disease risk factors in 12 weeks.

A water-shed paper recently published in the journal Science reported that the primary circulating ketone (b-hydroxybutyrate or BOHB) is a potent regulator of a group of genes that protect cells from oxidative stress. This protects the body from inflammation that lies at the heart of life-threatening disease.

Two recent studies have showed that BOHB is a longevity metabolite. One study showed that elevated BOHB levels extended life span by 26% in worms, and the other showed that BOHB corrected the metabolic defects in a mouse model of accelerated ageing.


One poorly explored variable has been fatty acid composition – the percentage of saturated, polyunsaturated and monounsaturated fats, as well as the amount of linoleic acid (an omega 6 fatty acid) and alpha-linoleic acid (an omega 3 fatty acid) in all the different oils.

For ordinary living, here is an example of meals for a Day in the Low Carb Life:


black coffee

4 sausages


2 cups mixed greens

6 oz water pack tuna

10 black olives

½ cup blue cheese dressing (yogurt)


2 oz mixed nuts, broth

2 oz soft cheese with

6 oz celery


8 oz tomato bisque

8 oz steak

4 oz buttered green beans

4 oz sautéed mushrooms

4 oz maple walnut ice cream

(Made w/ sucralose/xylitol)

This gives a total of Total: 2100 kcal fat, 600 protein, 150 carbs (74% fat, 5% carb, 21% protein)

How to keep up a ketogenic diet:

There are 7 steps to sustainability:

  1. Moderate protein
  • 5-2 g/kg (based on reference body wt.)
  1. Enough energy
  • Mostly from fat, no fear of saturates
  1. The right kinds of fat are critical
  • Eat monos and saturates for fuel
  • Limit high polyunsaturated sources (soy, corn, cottonseed)
  1. Mineral management
  • Supplement sodium 2 g/d for carbs < 50
  • Replace magnesium to stop muscle cramps
  1. When in doubt, eat less carbs
  2. When in doubt, eat more fat
  3. Pleasure and satisfaction
  • Satiety, Taste, Variety
  • Guilt-free eating

We also need to rethink sodium guidelines. Studies have not taken into consideration populations that were in nutritional ketosis, which would limit the upside risk of sodium intake while increasing the downside risks.


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