Stop turning food into an identity. Use the right fuel for the mission.

Within the past year, I've had many ketogenic/carnivore influencers, as well as many others in the comments, saying to me, "If you need carbs before or after training, you're not metabolically flexible."

My short answer:

"Using carbohydrates strategically doesn't prove metabolic inflexibility any more than using a higher gear on a bicycle proves your legs are weak. Metabolic flexibility means I can efficiently burn fat when the workload is low and carbohydrates when the workload is high. I'm not married to either fuel source—I use the one that best matches the job."

Now this is usually the part where I have to give my usual disclaimer so I don't get relentlessly attacked and people in the carnivore/keto space don't lose their minds. If you are thriving on a ketogenic or carnivore diet and getting everything out of it that you expected, then by all means continue to do so. I'm not here to say there is one size that fits all. I'm simply saying that there are many ways to skin a cat, and while one person may thrive in one direction, others may thrive in another. My insight is from one who has experimented deeply with both in a hard training and high output environment for many, many years. Literally decades. Many people in this internet age have shiny object syndrome and get caught up in online echo chambers. Free yourself. Onward...

Let's break it down. 

This is what "metabolic flexibility" actually means. 

Metabolic flexibility is simply the ability to efficiently switch between fat and carbohydrate depending on what's being asked of the body.
A metabolically flexible person can:

• Burn mostly fat while sleeping, walking, easier rucking, or sitting at a desk.
• Burn increasing amounts of carbohydrate as exercise intensity increases.
• Return to primarily fat oxidation when the demand is over.

That's literally what healthy human metabolism was designed to do.
Being able to use carbs isn't evidence that you're metabolically inflexible.
It's evidence that your metabolism works.

I made the mistake of believing that I needed to completely exclude a major macro nutrient and tirelessly work on exercise efficiency in order to build "metabolic flexibility". I did this for not just weeks or months, but I did it for literally years at one point. And found for my body and my level of output, it never quite reached the level that I desired or found completely sustainable. And I've experienced the same with dozens and dozens of clients over the last year especially. Real data from real people. 

Carbs are a tool, not a requirement. No, carbohydrates are not required to build muscle. No, they aren't required to survive. But neither is larger amounts of protein, copious amounts of fat. Neither are barbells or lifting straps. Neither is creatine. Neither is refrigeration nor air conditioning. We use tools because they improve performance And quality of life. The amount of protein actually required to sustain life is extremely small. But we're not looking for the absolute minimum effective dose to not die. Rather, we're looking for the precise amount required to generate the greatest result. There is no human life requirement for exogenous saturated fat either. But many carnivore and keto influencers say that substantial amounts are an absolute necessity. And I'm sure it is for their level of output and the greatest quality of living. The truth is, the only dietary fat needed for human survival is Linoleic acid (omega-6) and Alpha-linolenic acid (omega-3). 

The question isn't: "Can I survive without carbs?" The question is: "Can strategically timed carbohydrates improve my performance, recovery, muscle retention, and training volume?" For many athletes the answer is yes.

Exercise physiology hasn't changed When you perform:

• heavy squats
• repeated sprints
• high-volume bodybuilding
• CrossFit
• strongman
• GORUCK events

Your body preferentially uses glycogen because glycolysis can produce ATP much faster than fat oxidation.
That's not an opinion. That's basic exercise physiology. Fat oxidation is incredible, until intensity rises. Then carbohydrate becomes increasingly important.

Being fat-adapted isn't the same as being optimal. A carnivore athlete may complete a hard workout. A mixed-fuel athlete may complete that same workout with:

• more total volume
• more power output
• higher bar speed
• better recovery
• less perceived effort

Those are measurable outcomes. If the goal is maximum performance—not simply completing the workout.

Context matters.

A 45-minute Zone 2 ruck? Probably don't need carbs.

A twelve-hour GORUCK Tough challenge? Maybe (and I have found through exhaustive experimentation that for myself this will be an x-factor).

A brutal leg workout with 20 hard sets? Quite possibly.

A bodybuilding prep where every ounce of muscle matters? Absolutely worth considering and one can make the argument that it would be absolutely optimal.

Fuel should match the demand.

The irony is many influencers define metabolic flexibility as: "I never need carbs." That's actually the opposite of flexibility. Real flexibility is: "I can function extremely well on fat, and I can also utilize carbohydrate efficiently when it gives me an advantage."

​That's flexibility.

The goal was never to prove you can suffer on the least amount of fuel possible. The goal is to become stronger, faster, healthier, and more capable. Real metabolic flexibility isn't refusing carbohydrates or worshipping them—it's having the ability to efficiently use both fat and carbohydrates depending on what the mission demands. The physiology is settled. The debate isn't about biology anymore; it's about ideology. I'll choose performance every single time.  You choose what's best for you, and then we can all get along. 

*Want to fast track your results and become more dangerous again? Check out my Iron Forty programs or get my popular new book Iron Forty available for download immediately at www.robgoodwinfitness.com   

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