We love flexibility, and we humans are particularly good at it. Noah el Harari (he wrote Sapiens), credits flexibility and adaptability as the reason we’re still here, and you speak to anyone in the current day and there’s a serious desire to have a flexible life, without rigidity or structure.
It’s defined as the ability to be easily modified, or the willingness to change or compromise – don’t we all want these. But what about flexibility in the body? No, I’m not talking about being able to do a back bend, I’m talking about the ability to shift between fuel sources depending on the situation – this is the modern phenomenon of metabolic flexibility. Yes, this does means that you can burn fat when you want!
So, What is It?
Cell defines metabolic flexibility as “the ability of an organism to respond or adapt according to changes in metabolic or energy demand as well as the prevailing conditions or activity.” Goodpaster (2017).
Though the sexier definition comes from Dr Mike T Nelson, who states that “Metabolic Flexibility enables you to (1) transition between fats and carbohydrates so you can burn more fat when you’re not exercising; and (2) use carbohydrates when you are exercising to fuel that activity and perform at a higher level.”
Forget bulletproof coffee, this sounds like the ultimate “biohack.”
Not only does Metabolic Flexibility have huge effects on looking better naked, but it can drastically improve one’s overall heath and quality of life. In fact, our ability to be metabolically flexible has strong links with mitochondrial function, insulin sensitivity and oxygen utilisation (Goodpaster, 2017). It’s not a new concept either, metabolic flexibility has played a crucial role in our survival, as we would have frequent periods of fasting and indulging, forcing the body to go through physiological change to create a more robust human – you could easily argue that we wouldn’t be here if we didn’t have metabolic flexibility.
Kelley et al. (2002) sums it up well:
“Due to possible discontinuities in both the supply and demand for energy, humans need a clear capacity to use lipid and carbohydrate fuels and transition between them.(1)”
So let’s look at someone who’s metabolically flexible. These guys are more likely to be lean, active and can go long periods without food. Part of this is being used to using fat as a fuel source and not having huge peaks and troughs in energy that’s dictated by how log ago their last top up of sugar was. There have been correlations with those who undergo intermittent fasting and a ketogenic diet being more metabolically flexible, but then there is solid research on hunter – gatherer communities who live mostly on carbohydrates demonstrating a good level of metabolic flexibility as well. So this topic goes beyond macros and into about lifestyle, genetics and the microbiome.
On the other hand, let’s look at someone who is “metabolically inflexible.” This person is probably overweight, inactive and might kill someone if they don’t have access to a bagel. Why? Well, their energy peaks and slumps throughout the day as they move from each sweet treat to the next…. These folk are “sugar burners” Many of these folk are victims to the modern food system that’s littered with refined carbohydrates, and are supported by it as well (it’s like an abusive relationship). “A little Hungry? Great! Have this delicious cheap sweet thing then come back in two hours for another.”
As we know, this leads to huge blood sugar fluctuations, overconsumption of nutrient poor and calorie rich food, obesity and dietary related disease. These guys have a really tough time burning fat and getting lean, as they’re running on sugar. Once sugar depletes, there’s a serious craving for more sugar.
Okay Steve, I’m sold, how do I become more metabolically flexible?!
How to get more metabolically flexible.
Shocker I know, but if we move our bodies, we become healthier. Which exercises make me more metabolically flexible you ask? Well, it seems that constant movement (not being a desk jockey) with high intense resistance training is a great combo. So go for that morning walk and follow it up with a weights session, and throw SOME higher intensity stuff in there…
2. Cut down on refined carbs:
Breads, bagels, pastas, sweets, they’re all going to halt your ability to become a “fat burner.” Why? Well the body is likely going to be using these as fuel first, kind of like paper on a fire, but we’re continuing to top up on paper (or bagels) then your body doesn’t have an opportunity to access fat stores for energy.
The most important one on the list, a bad night of sleep is the best way to become sugar dependent – Noticed how good all that junk food looks after a night of bad sleep? The Journal of Clinical Endocrinology and Metabolism found that ONE night of shortened sleep led to insulin levels that looked like that of a type 2 diabetic in healthy people. Good luck saying “no” to cake at the office in this situation.
4. Follow time restricted eating:
The whole intermittent fasting phenomenon follows similar principles of metabolic flexibility. Giving your guts some time between meals and eating in a window (8 hours seems to be opimum) has shown to improve hunger swings, fat burning capacity and metabolic flexibility. An easy way to do this is having your first meal at 10am and your last meal at 6pm.
5. Chill out
Most of the points above are redundant if we don’t consider the impact of stress on the system. The father of this topic, Dr. Robert Sapolsky has studied the impact of stress and it’s impact on homeostasis at length. His findings show that chronic, prolonged stress alters insulin levels, blood sugar levels, frontal lobe function (responsible for decision making), and has a direct impact on our ability to burn fat.
Concluding, the phenomenon of metabolic flexibility is a key health marker and has a significant impact on our ability to not only look better naked, but to build a more resilient body that’s resistant to dietary related diseases. As always, it takes a holistic approach to achieve this level of health, taking into account fitness, nutrition and lifestyle factors.
Want to become more metabolically flexible? Join our next MDN challenge!
Donga et al. (2010) A single night of partial sleep deprivation induces insulin resistance in healthy subjects. The Journal of Clinical Endocrinology & Metabolism, Volume 95, Issue 6, 1 June 2010, Pages 2963–2968
Freese et al. (2017) The sedentary revolution: Have we lost our metabolic flexibility. https://www.ncbi.
Goodpaster, B., & Sparks, L (2017) Metabolic Flexibility in Health and Disease. Cell Metabolism. https://doi.org/
Kelley, D.E., He, J., Menshikova, E.V., Ritov, V.B. (2002) Dysfunction of mitochondria in human skeletal muscle in type 2 diabetes. Diabetes. 51(10).
Moro. (2016) Effects of eight weeks of time – restricted feeding (16/8) on basal metabolism, maximal strength, body composition, inflammation and cardiovascular risk factors in resistance trained males. Journal of Translational Medicine