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LIVING FIT & WELL The Importance of Being Metabolically Flexible
LIVING FIT & WELL The Importance of Being Metabolically Flexible
By Mark Nemish
In previous columns, I established the benefits of greater levels of fitness in terms of enhancing physical performance, reducing mental/cognitive decline, and staying free longer from all-cause mortality like heart disease and some cancers.
Central to these positive effects of exercise are better functioning and more abundant mitochondria which can be effectively enhanced with all forms of exercise, especially endurance and high intensity interval training (HIIT).
In this issue, I’ll discuss the importance of how your body uses fats and carbohydrates to produce energy (ATP) as it relates to your health.
When you’re at rest or performing low levels of exercise like walking or light biking, your body will rely on a combination of stored fuels such as carbohydrates and fats, to produce ATP. Those in better physical shape (higher VO2max) will be able to utilize a much higher percentage of energy from stored fat than those in poorer physical condition or in unhealthy states.
For example, a recent study demonstrated that elite endurance athletes can utilize fat at a rate of three-fold in comparison to subjects who have Metabolic Syndrome even when both groups are exercising at the same relative VO2max.
As a result, those in unhealthy states like Type 2 Diabetes (T2D), rely more on carbohydrate substrate for energy in resting and low-level exercise conditions.
Higher level athletes have a much greater ability to shift their fuel usage based upon the demands placed on their bodies.
For example, when performing HIIT, athletes will have a much greater ability to mobilize and use stored carbohydrates as fuel. The ability to shift from a predominance of fats for fuel in low level energy demands to a predominance of carbohydrates in highly intense exercise is an example of great metabolic flexibility.
Those in unhealthy states lack the ability to effectively transition between fats and carbs for energy and thus are metabolically inflexible. That’s partly due to the fact that being sedentary does not create those energy demands and thus adaptation.
One way to assess this is by measuring fasting lactate. One of the end products in the breakdown of carbohydrate (glucose) in the body is lactate. I typically measure my clients’ fasting lactate in the morning to assess their fuel (fats & carbs) utilization overnight.
Fasting lactate is a great proxy for metabolic health and higher levels of it are the result of a greater reliance on carbs and indicative of poor health conditions like obesity, insulin resistance, and T2D.
All of these conditions are typically driven by a sedentary lifestyle and overnutrition/caloric excess. When people lose body fat by reducing their caloric intake and improve their aerobic capacity (VO2max), fasting lactate will significantly decrease, indicating a shift to utilizing more stored fat to fuel the body in fasting and low-level exercise conditions.
Some researchers have concluded that high fasting lactate may be an early predictor of metabolic disease. That signals the need for lifestyle change that would include diet modification and the implementation of a structured exercise program.
Mark Nemish is currently the owner/director of Precision Health Performance in Round Hill, a business dedicated to optimizing the health and fitness of people in need of lifestyle change. He was head strength and conditioning coach for the Washington Capitals (2007-23) and Nashville Predators (1998-04) in the NHL.
