One of the most popular trends in the nutrition and fitness landscape right now is the Ketogenic Diet. And as a performance-based nutrition coach, what matter most to me is can and will Ketosis impact performance, and if so, how. It is my job to educate myself, and research the benefits and potential detriments of any number of nutritional philosophies.

There is more than one way to skin a cat, and I won’t hang my hat on any one approach to solve everyone’s performance goals. The coaching process is an art, as much as it is a science.

Scientifically speaking, it is no secret that when you simply cut carbs down to 5-10% of your total caloric intake (the traditional Keto range for carb intake), performance suffers…big time. Not to mention you are pissed off and hungry all the time. At first.

However, employ some patience, execute the plan, and push through the suck, and you will see your performance escalate once again to the same, if not better levels of performance.

Science has proven that fats (in the form of fatty acids) fuel lower intensity training while carbs are the primary driver in higher intensity training.  High intensity training relies on the production of ATP.  ATP is the byproduct of glycogen being converted to lactate. This process happens almost instantaneously under the right conditions.  On the other hand, trying to get ATP from fatty acids happens about as quickly as drinking honey through a straw. Yes, that is slowwww.

If you deny the body carbs, thus glycogen for long enough, however, that honey heats up and starting flowing at record rates. Fuel problem solved.  This process by which fatty acids begin to replace the absence of carbs for fueling high intensity training is called Ketoadaptation. The process varies from person to person, based on genetics, training and adherence to the dietary specifications, but typically it takes about 3 weeks.

This article tells it all, and in many people’s opinion is one of the most influential still in the argument for the low carb, high fat approach of a ketogenic diet.

Phinney, Bistrian, Evans, Gervino, and Blackburn.

The human metabolic response to chronic ketosis without caloric restriction: preservation of submaximal exercise capability with reduced carbohydrate oxidation (1983)

Using cyclists as subjects they took them through a four week, isocaloric (meaning they ate the same number of total calories as control subjects) but super-low carb (~20 grams of carbs per day). This is what happened…

First a little science break. There are several scientifically valid ways for measuring physical aerobic capacity, and overall fitness levels.  One is called VO2 max.  In short, this is the Maximum Volume of Oxygen that the body can deliver to working muscles to delay fatigue and prolong physical performance.  In other words, how efficient are you at moving oxygen through the body.

Then we have the RQ, or the Respiratory Quotient. Th

e RQ is a numerical value which reflects the percentage of caloric consumption coming from Carbs, and the percentage coming from Fats at any given time.

Once in a Keto adapted state (meaning Fats became their primary fuel source), the cyclists in the aforementioned study showed no drop in overall level performance levels as compared to when they were initially burning carbs. In other words, their VO2 /Fitness Capacity levels were unaltered, but their RQ decreased significantly. As you can in the chart to the left,  a lower RQ means greater Fat utilization.

What happens during Ketosis that allows an athlete (or anyone for that matter!) to train at the same, if not higher levels as they would on high carb?

In our fun honey image from earlier, the honey coming through the straw is stored body fat, the straw is mitochondria, and ATP is the rate at which the honey enters your mouth.

So how would you get more honey in your mouth, more quickly? Use more straws. Fatter straws…or “heat up” the honey with some ketones so it flows more readily. More than 3 weeks on a ketogenic diet and you have more, better mitochondria and can generate ATP just as fast as a high carb diet.

I know…ATP, VO2, mitochondria. You are sweating just thinking about Freshman chemistry finals. All you need to know is…more mitochondria, and less resistance to the flow of fatty acids through the introduction of Ketones, and you are an ATP making machine. However, this is also why prior to keto-adaptation athletes bonk. Hard.  You can’t ride the fence. You have to

either stay the course, and enter ketosis, OR you have to eat some dang carbs!

Moral of the story…it takes either Ketones + Mitochondria or Carbs to derive and deliver the fuel that is necessary to drive high level physical, and mental performance. You can be an athlete and succeed on low carb, keto diets ONCE you have reached that adapted ketogenic state. The in between will suck. The restriction on the foods and protein intake will not be easy or sustainable for many…but long term performance levels will rebound. If you are interested in giving it a try or just want to discuss a performance fuel plan that is right for your body and your goals. Give me a shout!