What If Fat is the Solution? An Interview with Drs. Jeff Volek & Stephen Phinney Part 1

What If Fat is the Solution? An Interview with Jeff Volek & Stephen Phinney by Dana Carpender

Written on January 6, 2013, updated on April 4, 2023.

This article was originally written in 2013 by Dana Carpender in an exclusive interview with Drs. Jeff Volek and Stephen Phinney for our April 2013 digital issue of CarbSmart Magazine. The article discusses the benefits of a low-carbohydrate, high-fat diet and the misconceptions surrounding this dietary approach. While the article was originally published a decade ago,we feel that the information is exciting enough that it deserves another outing, this time in a free venue. Dana hopes to re-interview either or both of these gentlemen soon.

Jeff Volek and Stephen Phinney
Jeff Volek and Stephen Phinney

Drs. Volek & Phinney Reveal Secrets of The Art & Science of Low Carbohydrate Performance – An Exclusive Interview by Dana Carpender

The Art and Science of Low Carbohydrate Living“We just don’t have enough research yet,” is a standard argument of low-carb detractors. This is untrue, there is quite a lot of research, and the body of knowledge expands daily. (It also ignores the fact that there was never much evidence in favor of a low fat/low cholesterol diet, but that’s another article.) Among the most committed researchers are Stephen Phinney and Jeff Volek. Written for doctors, their book The Art And Science Of Low Carbohydrate Living is perhaps the most complete book written on the topic to date.

The Art and Science of Low Carbohydrate PerformanceDespite the increasing acceptance of carbohydrate restriction for weight loss, there is still a general belief that serious exercise requires carbohydrates, even “carb-loading.” Steve Phinney, an enthusiastic endurance athlete, started researching the effects of carbohydrate restriction on athletic performance as far back as the 1970s, and Jeff Volek, aware of this research, experimented with carbohydrate restriction while powerlifting. Their love of sports and interest in ketogenic diets led to The Art And Science Of Low Carbohydrate Performance, very possibly the only book of its kind.

Dana: Drs. Phinney and Volek, thanks so much for agreeing to this interview. Your work is some of the most exciting stuff going on in the low-carb world. How did you get interested in carbohydrate restriction? It’s been an article of faith in the sports world, in particular, that carb-loading is essential to performance; what made you look at the opposite tack?

exercise - hiking - getting active again
Photo by Toomas Tartes on Unsplash

Steve: As a life-long endurance athlete (cycling, hiking, mountaineering), I’ve experienced many episodes of hitting the wall (aka bonking), which I learned to avoid by constantly eating carbs. So when I started using a ketogenic diet to treat severe obesity in the 1970s, I cautioned my patients that their exercise capacity would be limited due to their very low carb intake. However, one of my patients, a middle-aged guy, trained for and ran a 10K race in the latter half of losing 80 pounds on a very low-carb diet. His comment that he felt like crap for a few weeks, but then got his power back, prompted me to do my first study in untrained obese subjects in 1977. That paradoxical result led me back to graduate school and my Ph.D. research with highly trained athletes, which reinforced and extended those original observations. So way back then, we punched a big hole in the carbohydrate-loading hypothesis even though we were trying to prove that it was correct.

Jeff: like many people, my initial encounter with low carbohydrate diets was through personal experimentation. I had just completed dietetic training in the early 1990s and was obsessive about limiting fat in my diet. On a whim, I decided to try the Atkins Diet, and was shocked at how much better I felt. This ignited a passion to study the details of carbohydrate restriction that has continued to this day.

Weightlifting and Power Lifting
Photo by John Arano on Unsplash

Early on I became aware of Steve’s work published a decade earlier. I remember thinking how bizarre it was that virtually no one (including Steve) conducted follow-up studies to confirm and expand these provocative results. At this time I was competing in powerlifting, and found that my strength-to-mass could be improved on a very low carbohydrate diet. I started planning low-carb experiments in the mid-1990s while a doctoral student. My doctoral dissertation focused on lipoprotein responses to a ketogenic diet. The positive results inspired me to pursue a series of experiments that eventually led to crossing paths with Steve. Then things got really interesting, and fun!

Dana: While I exercise, I have never been a serious athlete — I was a fat, awkward kid — but Jeff, your personal reaction to Atkins is so familiar to me — trying a low carbohydrate diet and being shocked and dazzled by how much better you felt, and how quickly. I didn’t even go through the “Atkins Flu” — within three days my energy level had skyrocketed. Once that happens, it’s obvious that everything you thought you knew about nutrition was wrong. It’s a powerful thing. Maybe most exciting from the standpoint of having been born with a hinky carbohydrate metabolism, it’s an amazing thing to suddenly have so much energy you want to exercise.

What can an athletic individual expect in the first few weeks of carbohydrate restriction? How rapidly will things change?

Jeff Volek and Stephen Phinney
Steve and Jeff: Within two days of cutting carbs below 50 grams per day, the bottom falls out of high-end performance (i.e. anything sustained above 50% of peak power, or alternatively a hard resistance exercise workout). Trying to avoid falling off that cliff by easing down gently on carbs over a matter of weeks delays the plunge, but doesn’t seem to avoid an obligate period of adaptation. People vary in how long it takes to get their power back once they are fully ketogenic, but most athletes (and untrained folks as well) feel that they’ve turned the corner after 2 weeks, and are back to or above their prior capacity in 4-6 weeks. After that, any additional changes are more subtle. But whether due to fine-tuning their diet, changes towards a leaner body composition, or adaption in muscle architecture, some athletes report that they function even better after 6 months of nutritional ketosis than after those first 6 weeks.

Dana: Seems easier to me to simply go for it, but then I’m that sort of person.

It seems likely that a keto-adapted individual would have greater endurance than when they were relying on a glucose-based metabolism, since even slim people have enough fat to fuel them for quite a while. Is this your experience?

exercise - running - getting active again
Steve and Jeff: Yes, from a purely metabolic standpoint humans have a much larger fat than a carbohydrate fuel tank. A 150-pound male marathon runner at 7% body fat (or a 115-pound female runner at 10% body fat) will have over 35,000 Calories of fat stores, but never more than 2,000 Calories of carbs as glycogen. A limitation of the high-carb approach is that the frequent consumption of sugars and starches limits access to the fat fuel tank, in essence locking an athlete into a glucose-based metabolism. After 4-6 weeks of keto-adaptation (the process of switching over to a fat-dominated metabolism), muscle glycogen stores are cut in half, but its rate of use is reduced by a factor of 4. In its place, the body adapts to use fatty acids and ketones as its primary fuels, so that moderate supply of glycogen actually lasts longer.

Since a typical marathoner burns about 100 Calories per mile, runners learn by experience how to make those 2,000 Calories of glycogen (i.e. the amount of glycogen achievable by carb loading) last to the finish line. But if they get it even slightly wrong (i.e. running out of glycogen at mile 24 or 25), they may end up walking the last mile or two.

ultra-marathon events
Photo by Mārtiņš Zemlickis on Unsplash

Not surprisingly, it is in ultra-marathon events (Ironman triathlons, 50- and 100-mile races) where the keto-adapted athlete can have a major advantage over standard high-carb fueling strategy. In the last few years, low-carb runners have begun to not just win but even set course records in these longer events.

Dana: Very interesting; I didn’t realize that marathoners had to make mental calculations of how far they can go before they crash. I wonder how long it will be before word of superior endurance on a ketogenic diet spreads among serious runners?

Back in 1996, I had a massage client who was a serious runner — competed at Indiana University here in town. She was, of course, eating a low-fat diet with tons of carbs. Most people would have thought her to be in terrific shape, but as her massage therapist, I knew what kind of a beating her body was taking. More interesting, though, was the fact that she was often ill — colds and other viruses seemed to find a friendly environment in her “healthy” body. She missed out on the trials for the Goodwill Games because she came down with whatever bug was going around.

Enter The Zone had recently come out, and I tried to convince her to read it, but she was convinced that she needed to carb load to be competitive. I have wondered since how she was, and if she ever tried carbohydrate restriction. I’ve never been a competitive athlete — heck, I was literally a gym-class drop-out — but I suspect that word spreads in the community.

In anatomy and physiology class, they taught us that aerobic exercise could be fueled by glucose or fat, but that anaerobic exercise, of necessity, demanded glucose. Yet I have made good progress with heavy resistance exercise — using a Slow-Burn style workout — while eating a very low carbohydrate diet and even had some good workouts while fat-fasting. What’s up with anaerobic exercise and carb restriction? Do, say, bodybuilders actually need some carbs, at least immediately prior to lifting? How about sprinters?

Steve and Jeff: In the end, all exercise is fueled by high-energy phosphates (AtP and creatine-phosphate). At rest, our muscles always have a small amount of these instantly available, so the amount of exercise you can do is determined by how quickly these high-energy molecules can be regenerated once exercise begins. As we noted previously, being keto-adapted allows a much higher percentage of muscle energy to come from fat. This works not just during continuous aerobic exercise, but in between lifts when doing a resistance workout. Thus a keto-adapted person uses less glycogen to replete these high-energy phosphates as long as s/he keeps breathing.

Dana: What I’m hearing is that I’m using my glucose and glycogen during the actual lift, but in even the few moments between reps I’m burning fat and/or ketones. Nifty!

exercise - sprinting - other activities - getting active again

Steve and Jeff: Sprinting is a bit of a different dynamic, depending upon the duration/distance. Since muscle glycogen is somewhat reduced but certainly not eliminated, it can still be accessed for anaerobic metabolism to lactate. Thus short sprints are unlikely to be affected by being keto-adapted. However, coming up with a ‘kick’ in the last 200 meters of a 1,500-meter race might be a problem. On the other side of the fence, however, doing 15-second intervals every minute or two tends to be well tolerated because of the speed of recovery in the keto-adapted state.

‘Recovery’ is a very important concept in sports nutrition, albeit one that is complex. In the very short term (i.e. a few seconds), it involves regenerating high-energy phosphates within muscle cells. This can come from glycogen, fatty acids, ketones, and even branched-chain amino acids. In the time frame of seconds to minutes after intense exercise, recovery means clearing the lactate buildup in muscles and in the circulation. Lactate (and its associated hydrogen ion — i.e. acid) is the primary driver of the hyperventilation that follows anaerobic exercise.

So when your breathing calms down after a sprint, you can know that this phase of recovery has been accomplished. In part due to the fact that less lactate is made for any one level of exercise in the keto-adapted state, most athletes comment on how much less labored their breathing is in this phase compared to when on a high-carb diet.

The third phase of recovery happens during the day or two after an intense workout. In this phase, muscle damage is repaired and fuel supplies within the muscle cells (both fat and glycogen) are restored. It is a little-known fact that we store equal amounts (on a caloric basis) of glycogen and fat in our muscle cells. And because fat mobilization is enhanced and glycogen use is reduced, this phase of recovery is more prompt in the keto-adapted state.

exercise - inflammation
Photo by Towfiqu barbhuiya on Unsplash

But perhaps more importantly, because intense exercise causes muscle inflammation (which translates to soreness and lethargy), a key factor in this third phase of recovery is how much inflammation you experience and how fast it is resolved. In prospective, randomized trials, we have demonstrated that a well-formulated low-carb diet results in reduced biomarkers of inflammation ( i.e. those things like CRP and white blood cells that indicate how much injury has occurred). While biomarkers can be misleading, many athletes report that this third phase of recovery is much, much quicker when they are keto-adapted. Obvious examples of this are two keto-adapted ultra- endurance runners (one age 41 and the other age 65) who each recently completed back-to-back 100 mile races on successive weekends.

And in the case of the 41-year-old, he not only won both events but both times beat his next nearest competitor by over an hour.

Dana: 100 mile races in middle age? Beat the competition by over an hour? That’s pretty amazing, though of course at that distance differences in time would be magnified. Again, surely word of this sort of performance will spread through the running community.

exercise - skiing
Photo by Razvan Chisu on Unsplash

Steve and Jeff: The benefits of fast recovery in the keto-adapted state are not limited to ultra-endurance athletes. Other examples of athletes employing a low-carb diet include the tennis player Mardy Fish and the skier Lindsay Vonn. Both have noted in interviews that both body composition and recovery are improved on a low carb diet. Given how much science there is supporting low fat, high carb diets, how can this be? Well, most research has involved a few days of a defined diet followed by a single test. But in the real world, athletic success is defined by how you do month after month, season after season. If you can have better fuel flow and less inflammation month upon season, perhaps the few technical issues with low carb will be overcome by its cumulative benefits.

Dana: Testing after just a few days on a low carbohydrate diet is one of those flaws in research I see over and over again, and it makes me crazy. A few years back, a study came out purporting to demonstrate that a low carbohydrate diet hurt cognition, but again, it was after just a few days. I always want to ask these researchers: If you tested someone a few days after he quit smoking, would you expect his performance to be unaffected? Would you argue that his diminished performance was a reason he should not quit smoking, or that it was likely to be representative of the long term?

Steve and Jeff: Regarding dietary carb supplements before exercise — The scientific jury is still out for people in the keto-adapted state. After exercise? Yes, we still have more research to do, but if you make less lactate from glycogen and post-exercise make more of it back into glycogen, why mess up this elegant choreography with a bunch of glucose and fructose molecules that (beyond a few grams per day) our ancestors never had to deal with?

Dana: Makes sense to me.

Read Part 2 of Dana’s Interview with Drs. Volek & Phinney.

More Low Carb Recipes & Articles by Dana Carpender

Check Also

Low-Carb Holiday Gift Giving

Low-Carb Holiday Gift Giving – CarbSmart Podcast Episode 3

Low-carb holiday gift giving. Let's talk a little about low-carb gift giving. Low-carb gift giving? Sure, in a couple of ways. First, most low-carbers know other low-carbers. We're a friendly bunch. Just go on the low-carb cruise someday. You'll see. It's not that hard to find the perfect gift that supports your low-carb friends and family.


  1. Is there no other way to get the CarbSmart magazine than with an iPad? I have one, but it’s a first-generation iPad and cannot be upgraded to the required iOS 5.1. Can this somehow be viewed on a PC?

    • Hi,

      Currently the iPad is the only format we have, but we are working on making other formats available so all can access. It’s a very detailed process and we are working on it as quickly as we can. Thanks!

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.

%d bloggers like this: