Fresh, Small-Batch Nutrition for Better Health & Performance

Metabolic Flexibility by Daniel Matheny

After nearly completing this article, I had a thought that deserved to be noted first. As we dig into this you’ll probably find it odd that a nutrition company is diving into some methods that actually reduce the amount of the product you may consume!  What?! I know, but this is why I love the product and more-so the company, because they are interested in supporting what works WHILE selling their product. Similar to my coaching style, it’s about implementing the right things with simple ingredients to get the result.  

Could I use other products?  Yes.

Have I? Yes.  

Am I exclusive?  No. And I believe this allows me to express a less unbiased position.

But bottom line is each time I pick up Enduro Bites and see only a few simple ingredients that are chosen for specific nutritional purposes & properties, I know I’m consuming real food my body will use.  Ok onto the article……

While there are a lot of great research studies on ways to improve performance, many techniques simply don't pan out in real life. And honestly, if you took all the methods that claim marginal single-digit percent gains here or there and added them all up, we’d all be Olympians right?!  

Unfortunately, it just doesn’t work that way as it’s not isolated like in research. This is why I first gauge effectiveness on myself. Pending a positive outcome, I then look at how it can be best implemented by the typical athlete, with a regular job and family commitments, with training to maximize physical performance.

My clients don't have time do this experimentation, so I often serve as guinea pig for them.


A very fast guinea pig on the top step!

In this case, I was intrigued to improve performance with increased reliance on fat oxidation by utilizing a combination of fasted-state training and macronutrient manipulation.  Sounds fancy, but think skip breakfast and alternate higher periods of carbohydrate or fat intake. This falls into applying nutritional periodization (alongside training periodization in this case). If you’re not familiar with this concept, it involves systematically emphasizing phases of low-carb / high-fat diet (LCHF) with the more common high-carbohydrate diet, at different times.

Low-carb / high-fat diets have been shown to improve fat oxidation rates so athletes can work at higher percentage of maximum while still burning internal fat stores resulting in sparing limited glycogen stores (1, 2, 3). Typically these glycogen stores can be depleted in approximately 75-120 minutes, depending on work rate, body size and current substrate utilization, so increased performance is being achieved as they are spared until absolutely necessary.

Research shows, however, that consistently adhering to a low-carb diet results in down-regulated ability to utilize glycogen (4, 5) while working at a high intensity (i.e. above lactate threshold), thus limiting the anaerobic capacity. This is important since the key moments in most races are not when everyone is maintaining a steady pace (when fat is the predominant fuel source). Rather, it's when the pace gets spirited with accelerations, attacks, breakaways, etc., testing one another’s ability when groups are formed and separation occurs. Thus, you don't want to limit your ability to utilize glycogen at the time when it's most needed.

So, how can an athlete gain the advantages from following a low-carb / high-fat diet without suffering from this disadvantage?

My approach was completing cycles of both LCHF and higher carb (both chronic lengthy blocks or acute day-to-day variations) knowing full-well that without going “all-in” with one protocol, it may not elicit full reported benefits, but may limit the potential negative effects as well. And frankly I like food! So any diet that says “can’t eat” I don’t like.  This allowed me the mental flexibility to slide back and forth based on how I was feeling. If you’d like to read more on my personal experience, check out my N of 1 here, .

Consider this approach an attempt at metabolic flexibility. The intent is to up-regulate fat oxidation while not substantially down-regulating glycogen utilization. It’s not completely proven yet, although there is a growing body of research and current studies likely ongoing. In my eyes the principal holds some possibilities and with the limited but promising results I’ve witnessed, I’m willing to keep it in my arsenal of coaching tools.

If you’d like to try a few methods I use with my athletes, here are few:

  • stamina ride - eat a lower carb / higher fat dinner and either fast (or another LCHF breakfast or try the Beta Red Fasting bomb) before setting out on an aerobic effort or short intensity session.
  • prolonging any fueling within gradually increasing duration aerobic sessions as comfort and adaption occurs (i.e. gradually increase the duration until you consume an Enduro Bite to 45, 60, 90min or even longer into the session).
  • take plenty of food and drink plenty of fluids (as always) once you break the fast; you need to consume plenty at end of session to finish.  You don’t want to be stranded!

And just a note, be mentally prepared to have a lull in performance and not feel cognitively the best (6, 7, 8).  This can be just as mentally taxing as it is physically, because transitioning your body to oxidize fat isn’t immediate.  Adequate time and # of sessions must be completed to reap the effects, so start small and commit to the process.


  1. Lambert EV, Speechly DP, Dennis SC, and Noakes TD. Enhanced endurance in trained cyclists during moderate intensity exercise following 2 weeks adaptation to a high fat diet. Eur J Appl Physiol 69: 287–293, 1994.
  2. Phinney SD, Bistrian BR, Evans WJ, Gervino E, and Blackburn GL. The human metabolic response to chronic ketosis without caloric restriction: preservation of submaximal exercise capability with reduced carbohydrate oxidation. Metabolism 32: 769–776, 1983.
  3. Vaan Proeye K, Szlufcik K, Neilens H, Ramaekers M, Hespel P,. Beneficial metabolic adaptions to endurance exercise training in the fasted state. J App Physiol 110 (1): 136-245, 2011.
  4. Stellingwerff T, Spriet LL, Watt MJ, Kimber NE, Hargreaves M, Hawley JA, and Burke LM. Decreased PDH activation and glycogenolysis during exercise following fat adaptation with carbohydrate restoration. Am J Physiol Endocrinol Metab. In press.
  5. Havemann L, West S, Goedecke JH, McDonald IA, St-Clair Gibson A, Noakes TD, and Lambert EV. Fat adaptation followed by carbohydrate-loading compromises high-intensity sprint performance. J Appl Physiol 100: 194–202, 2006.
  6. Burke LM and Hawley JA. Effects of short-term fat adaptation on metabolism and performance of prolonged exercise. Med Sci Sports Exerc 34: 1492–1498, 2002.
  7. Burke LM, Hawley JA, Angus DJ, Cox GR, Clark S, Cummings NK, Desbrow B, and Hargreaves M. Adaptations to short-term high-fat diet persist during exercise despite high carbohydrate availability. Med Sci Sports Exerc 34: 83–91, 2002.
  8. Helge JW, Richter EA, and Kiens B. Interaction of training and diet on metabolism and endurance during exercise in man. J Physiol 492: 293– 306, 1996.

Daniel Matheny

Daniel doing what he does when not coaching or spending time with his family.

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