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Dr. Steve Phinney —

I can ride continuously for three hours and go 60 miles without any

hunger or food cravings or drop off in performance.  And I ride as well

in the last 20 miles coming home as I do going out.

Steve Phinney, can you tell us who you are?

I’m a medical doctor and have my training in internal medicine.  Early in my career developed an interest in nutrition and got a PhD in nutritional biochemistry.  That was 30 odd years ago, and since then my primary interests have been in weight management, ie, obesity, exercise and the human economy of the various fats we either put in our mouths or make in our bodies.

You’re a star in a Canadian documentary called My Big Fat Diet, because you helped a whole group change their eating habits to reduce insulin resistance and lose a lot of weight. you’re the co-author of a book about the Atkins Diet that’s been updated by you and two other clinician scientists.

Partially correct.  I had a bit part in My Big Fat Diet.  The star is Dr. James Wortman, a Canadian physician.  And yes, I’m a coauthor of the updated, new Atkins book which came out last March.

You’re also in the process of creating a new book that’s more technical about high fat diets.

That’s correct.  Dr. Volek, who’s one of the coauthors on the Atkins book felt, like me, that we needed to offer more information for people who are interested in the medical side of low-carb diets, with a more detailed explanation of the workings of the human body when carbohydrates are restricted.  It’s readable by both a health care professional and an interested, educated lay person.

Are you an athlete?

I’m physically active.  Though after high school, I’ve not been involved in competition athletics.

Do you eat a low-carb, high fat diet?

Yes, guilty as charged.

How low carb and how high fat?

I stay between 25 and 50 grams of carbohydrate a day.  I eat a moderate amount of protein.  It’s not a high-protein diet. I eat 2800 calories a day, and so if moderate protein is 500 to 600 calories a day and carbohydrate is around 100 calories a day, I’m eating over 2,000 calories of fat to maintain my body weight.  I run in the 70 – 80% of energy intake as fat.

From what most experts say about physical exercise, your muscles must be in shreds.  You’re not eating food that puts big stores of glycogen in your muscles.  Are you constantly sore and fatigued.

No, and one of the most fascinating things about switching from a high carbohydrate diet, which I used to follow, to a low carb diet, which I did six years ago . . . My primary form of purposeful exercise is bicycling, and my distances range from 20 to 60 miles, and I”ll do two or three rides a week.

I used to classify my rides as one banana rides, or two banana rides or three.  If I rode 60 miles, I had to take three bananas with me and had to eat one every hour.  Otherwise, I would be running out of power and dragging my tail home, or ordering a taxi.

That’s because my body would run out of carbohydrate fuel, and even though I had tens of thousands of calories of body fat, I couldn’t use it efficiently for exercise.  That’s where the concept of needing carbohydrates for exercise came from.

If a person goes through a few weeks of giving the body time to adapt to carbohydrate restriction–you do have to go through this gauntlet of forcing the body to adapt to a low carbohydrate diet, meaning let the cells alter their enzyme levels to efficiently burn fat for fuel, then, when I set out for a ride, I have 40,000 calories of body fat, and that’s accessible to me.

I carry no food now on my bicycle rides.  I carry water, but nothing that can raise my insulin levels, and now, I can ride continuously for three hours and go 60 miles without any hunger or food cravings or drop off in performance.  And I ride as well in the last 20 miles coming home as I do going out.

Maybe you’re riding more slowly than when you were doing the three banana rides.

No.  I ride as fast now, and I’m six years older now than I was when eating carbs.  And I’m at that point in life where my performance theoretically should be dropping off because of age, and I can ride 18 to 20 miles an hour still, and if some young person tries to speed up and go by me on a ride I can jump on their wheel and stay with them, just as well as I did ten years ago.

So you don’t need to have carbs to keep you going?  You don’t hit a wall the way you did when you were eating carbs?

That’s correct.  My gas tank got a lot bigger when I gave up carbs.  Because we can only store maybe 1500 calories as carbs.  If I burn 600 – 700 calories per hour, and I depend only on glycogen, that’s about two hours of fuel.  But if I have 30,000 to 40,000 calories of fuel in my fat, I can ride for days.

If you have that much fat on your body, does that mean you’re fat?

Body fat is in cells and there are cell membranes and cell nucleus and so on, and if you take that into account, then one kilogram, which is 2.2 pounds, contains about 7,000 calories of fat.  So if I have 40,000 calories of fat on my body, then I have about 6 kilograms of fat, meaning 12 to 14 pounds of fat on a body that weighs about 165 pounds.  I probably have more than that.  But my percentage of body fat . . . So around 15%.  Pretty lean for a guy my age.  A highly trained male marathon runner might be 8% fat, and if he weighs about 150 pounds, that’s about 12 pounds body fat, or about 40,000 calories of fat.

Are you the only person who uses a low carb diet and succeeds as an athlete?

Many people do, and they anecdotally note that their performance is as good or better than it was on high carbs.  Dr. James Wortman, for instance, the star of My Big Fat Diet, discovered in his 50s that he was a Type II diabetic, a disease that runs in his family.  He switched to low carb eating and his diabetes is completely controlled. He’s an avid skier, and I have personally seen him do a non-stop in a 5,000 foot descentof Whistler Mountain in British Columbia.  Obviously he’s not impaired by the way he eats.

But many sports physiologists warn that it’s not possible to be an athlete on a low carb diet.  They say that glycogen gets impaired on a low carb diet.  Glycogen is a starchy substance that’s made from sugar and stored in our cells.

Glycogen does go into the muscle and liver.  The muscle glycogen gets burned only in  that muscle.  The liver glycogen can be released into the bloodstream which is necessary to keep the brain happy.  The body’s energy economy includes not only fueling the muscle but fueling the brain.  If the brain fuel supply drops, you don’t feel well.  That’s called hitting the wall by runners and among bicyclers, it’s called bonking.

But the studies looking at carb dependency were all done for less than two weeks.  No study that went longer than two weeks has demonstrated the benefits of a high carb diet.  I personally put highly trained bicyclists on an Inuit diet for four weeks.  That’s the people who lived in the Arctic who ate a very low carb, very high fat diet.  For the first two weeks, the bicycle racers reported that their training was impaired and they didn’t feel well.  They were struggling with keeping up their training schedule.  But after two weeks, they reported feeling well and their performance, on tests, came back. and I knew this was true because I had to ride with them to keep them from stopping and eating something they shouldn’t.  We measured their peak aerobic power and their endurance time to exhaustion.  We did before and after performance, Same power curves on the indoor stationary bicycle at a set wattage over a period of time.  There was no reduction in performance after they had adapted for more than two weeks to a ketogenic diet.

As I did that project I became curious about people who had lived on that kind of Inuit Diet.  I read the journals of Arctic explorers.  One of them was a US army surgeon named Frederick Schwatka.  In 1881, he set out from the west coast of Hudson’s Bay.  He traveled the Arctic, overland with Inuit families, in search of a lost Royal Navy expedition that meant he traveled 15 months, over 3,000 miles on foot, in excellent health.

In his journal, he wrote, When first thrown wholly upon the diet of the native, one is ill-disposed to travel.  There is a weakness of the legs.  But this passes away after a few weeks and then long sledge travel are possible.

So it’s not just me.  It wasn’t just my bike racers.  It’s many people who find that when the body is given time to adapt, it’s remarkable in its ability to switch from dependency on carbohydrate, which is a very small fuel tank to the ability to access fat reserves without impairment of aerobic power and performance.

Steve Phinney, when you say adaptation takes two to three weeks, could someone be adapting by eating a low fat diet one day and a high fat diet another and gradually ease into this?

We have not studied that.  But informally, when people try that, they just feel lousy.  It’s a roller coaster ride, where you have a huge surge of insulin.  Then you deprive your body of the carbohydrate fuel.  The process of adaptation requires a consistent period of time for the body to make its peace with not having carbohydrates.  Most of the adaptation occurs in the first two weeks, but some of the fine tuning is going on four to six weeks after that.

What if someone’s afraid of fat, but they understand they need to cut back on carbs.  So they eat a 14 ounce steak at night to get energy from the protein in the steak.  Are they doing what you recommend.

The Inuit were not a literate culture, meaning they didn’t write down what they ate.  But people who lived among the Inuit and, I think, accurately recorded it, pointed out that the Inuit avoided actually eating lots of lean meat.  They had a name for an illness that happened if they ate too much protein and not enough fat.  The English translated the name of that s