These rival energy sources may not be mutually exclusive...

There are many schools of thought when it comes to fueling athletic activity. Some athletes prefer a mix of simple and complex carbohydrates – carbs are converted into glucose which can be used almost immediately as energy through the production of ATP and cell respiration. In recent years, as CrossFit and extreme fitness challenges have grown in popularity, athletes in search of a cleaner energy source have shifted toward ketones, and away from carbohydrate reliance– offering among many benefits sustained energy and anti-inflammatory support. However, a select few athletes have chosen to strategically utilize both. While at initial thought this may be perceived as redundant or ineffective, a closer look demonstrates why dual-fueling may be worth greater consideration.


Of all the energy options, carbs often seem the most convenient.  The body can only store limited amounts of glucose, so often, you can use energy from consumed carbs right away.  This is why athletes are advised to consume simple carbs pre- and post-workout.  Think of a 100-meter sprinter who throws back a teaspoon of honey right before a race.  Carbs provide instant gratification.  

Carbs are also readily available.  There’s no question that you have fruit, veggies, bread, rice, quinoa, or some other carb source in your kitchen.  They’re cheap, and in most cases, they’re fully stocked.

The downside is that carbs must be replenished constantly.  Because the body uses glucose right away, you must constantly refuel to stay energized.  If your nutrient timing is off or the quality of your carbs is poor, you might experience an energy crash, or end up storing the excess glucose as fat.


To have a beneficial presence of ketones in your blood stream, you must do one of two things – trigger ketosis by significantly cutting out carb intake for an extended period or consume exogenous (supplemental) ketones.

If you’re keeping your body in a constant state of ketosis through diet, your daily macronutrient breakdown might look something like this:

  • ·       Carbs: 30-50 grams per day (5-10% of total calories)
  • ·       Protein: 0.8-1 gram per pound of bodyweight (20% of total calories)
  • ·       Fat: 70-75% of total calories

What is unique about ketones is that no matter how they are derived, naturally produced or supplemented, they have the ability to break the blood brain barrier and provide immediate energy to the brain and organs, making them the body's preferred energy source. The energy from ketones is more stable and does not require constant refueling since there are significant natural energy stores in the form of fat and/or glycogen stores that can be used after depletion. Perhaps most notably to performance, ketones produce more ATP per unit of oxygen than glucose. This becomes especially relevant to high performance athletes who can benefit from producing greater power with less oxygen demand. 

Carbs + Ketones

So now that we know ketosis is typically viewed as being triggered when the body doesn’t have enough stored glucose for energy, and how carbohydrates are often deemed as the convenient choice for athletes, we understand why common knowledge would suggest that you fuel with either carbs or fat, but not both. However, a study from Peter Attia, MD further suggests this to be misconception.

In the study, Attia participated in two extreme bike rides on back-to-back days.  The rides consisted of 110 miles each, with strong winds, steep inclines, and high riding speeds.  Prior to the rides, Attia’s body was in ketosis.  On the days of each ride, however, he bumped up his carbohydrate intake to 321 grams – significantly higher than the recommended 30-50 grams.  The expectation was that his body would drop out of ketosis and shift back to using glucose for energy, since it was so plentiful.  But that didn’t happen.

The morning after each ride, his measured BHB levels demonstrated that his body was still in ketosis, despite dedicating nearly a quarter of his diet to carbs. Attia’s conclusion was that ketosis and carb tolerance are dependent on the individual’s needs and activity level. But even if ketosis isn't your focus. Can this "dual-fueling" thing help your performance? Such evidence suggests, yes. Ketones are burned first by the body for energy. Which means that Peter, and other endurance and high-performance athletes, are using ketones first, reserving other stores, such as glucose/carbs and glycogen stores for use after these ketones are depleted, thus significantly prolonging the period of time that they are able to perform. While they are not utilized at the exact same time, by doubling up on these two energy sources, the body naturally prioritizes energy use in a way that may seem to suggest that the use of these two simultaneously may be superior to heavy reliance on one or the other if you are an endurance or high-performance athlete.

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