The idea that we humans burn glucose for fuel is known by most people, but the idea that we have 2 primary sources of fuel to utilize should be equally known and utilized by all in my opinion. There are so many health benefits to being metabolically flexible, not to mention that it is a natural state that enabled paleolithic man to survive and evolve into the human beings we are today.
What Is Metabolic Flexibility?
Metabolic flexibility refers to the ability of an organism to adapt to changes in nutrient availability and energy demands by efficiently switching between different fuel sources and metabolic pathways. In this case, we are referring to the use of glucose and ketones (the by-products of fatty acid metabolism) as the 2 fuel sources every human should efficiently be burning.
When we are metabolically flexible, our body has the ability to effectively use carbohydrates, fats, and proteins for energy production and to switch between these substrates depending on the availability of nutrients and the energy demands of the body.
There are a number of health and performance benefits to metabolic flexibility including:
Improved Energy Levels: Metabolically flexible individuals can efficiently switch between fuel sources and maintain stable energy levels throughout the day. For example, the energy highs and lows one can experience when primarily burning carbohydrates for fuel are eliminated. One of the first benefits I experienced once I became metabolically flexible by following an intermittent fasting protocol called Time Restricted Feeding is that I no longer experienced dips in energy which would lead to me being ‘hangry’ after a few hours of not eating. In between meal snacks were no longer needed.
Better Blood Sugar Control: Metabolic flexibility helps to regulate blood sugar levels by efficiently using glucose and switching to alternative energy sources when glucose is scarce. For example, when glucose is scarce metabolic flexibility enables the body to produce glucose from other sources such as amino acids produced through protein turnover (not from muscle tissue) and glycerol in a process called gluconeogenesis. Another example of how metabolic flexibility uses alternative energy sources to maintain healthy blood sugar levels is through the production of ketones from stored fat when insulin levels are low. This helps to maintain blood sugar levels and provides the body with an efficient energy source other than glucose.
Enhanced Weight Management: Metabolic flexibility can help to optimize fat burning and reduce the storage of excess fat in a number of ways. It can enhance the body's ability to break down stored fat into fatty acids and glycerol for use as fuel. This process, called lipolysis, is a key step in fat loss. It can also enable the body to use fat as a primary fuel source during low to moderate intensity exercise, which can help to increase fat oxidation and promote fat loss. Metabolic flexibility is very effective at suppressing appetite, reducing food cravings, improving insulin sensitivity, which supports healthy fat burning.
Improved Cardiovascular Health: Metabolic flexibility can help to reduce the risk of developing cardiovascular disease by improving lipid metabolism and reducing inflammation. It can improve the body's ability to use and metabolize lipids, including cholesterol and triglycerides, which are key risk factors for CVD. Since metabolic flexibility can reduce inflammation, enhance insulin sensitivity and glucose control it can help to reduce the risk of developing metabolic disorders such as type 2 diabetes and obesity, which are associated with an increased risk of CVD.
Better Athletic Performance: Athletes with greater metabolic flexibility can perform better, retaining stable energy levels and focus more efficiently since they are able to utilize both glucose and fatty acids, (once converted into ketones by the liver) as fuel sources during various exercise intensities and durations. This eliminates the phenomenon of bonking during endurance sports.
How To Increase Metabolic Flexibility
1. Diet & Nutrition: Following a low-carb or ketogenic diet is one of the best ways to enhance metabolic flexibility. Beyond avoiding sugar and eating nutrient-dense whole foods, limiting carbs on a ketogenic or low carb regimen keeps insulin low and helps you stay in fat-burning mode.
When implementing a low carb or ketogenic dietary practice, it is important to focus on the following to optimize metabolic flexibility:
• Consume an adequate amount of protein to support muscle maintenance and metabolic function. The optimal amount of protein will vary depending on a variety of factors such as age, activity level fitness goals and health status, on average most healthy active adults should aim to consume 1.2-1.5 g/kg body weight. Choose high-quality protein sources such as grass-finished meats, poultry, wild caught fish, pasture raised eggs, and plant-based protein sources like nuts, seeds, legumes and organic tofu.
• Focus on Healthy Fats: They should comprise a substantial portion of your diet. When following a ketogenic diet, 5-15% and around 25-35% on a low carb plan. Incorporate healthy fats such as avocados, nuts, seeds, olive oil, coconut oil, and good quality proteins as mentioned above - eggs, grass-finished meats, fatty fish like salmon and sardines. These fats provide essential fatty acids/ketones as a clean source of fuel and help promote satiety.
• Include Non-Starchy Vegetables: Non-starchy vegetables are low in carbohydrates and rich in fiber, vitamins, and minerals. They provide important nutrients while keeping overall carb intake low. Examples include leafy greens, broccoli, cauliflower, peppers, zucchini, and asparagus.
• Practice Intermittent Fasting: Intermittent fasting can promote metabolic flexibility by extending the period of time your body is in a fasted state. This helps you switch from burning sugar to burning fat for energy. Consider incorporating a fasting window of 12-16 hours a few days a week or daily as you adjust to the practice. This is called time restricted eating (TRE). By compressing your feeding window, you suppress insulin for more of the day. Over time, your body’s insulin sensitivity improves. As less insulin is released throughout the day, more fat burning will occur.
2. Exercise: Implementing regular physical activity, including both aerobic exercises and resistance training can improve insulin sensitivity, promote fat burning, and enhance metabolic flexibility. Exercise promotes the utilization of fat as a fuel source during physical activity. Regular exercise, especially aerobic exercises like jogging, cycling, or swimming, increases the capacity of your muscles to oxidize fatty acids for energy. This improves your body's ability to burn stored fat, leading to enhanced fat loss and improved metabolic flexibility.
Resistance training promotes muscle growth and development. Increased muscle mass contributes to a higher resting metabolic rate, as muscles are metabolically active tissues. This means that you burn more calories even at rest, further supporting metabolic flexibility and weight management.
Intense exercise can lead to excess post-exercise oxygen consumption (EPOC), commonly referred to as the "afterburn effect." During this phase, the body requires additional oxygen to restore physiological functions and return to a resting state. EPOC increases energy expenditure, including the utilization of stored fat for fuel, which supports metabolic flexibility.
As you have read, there are a wealth of benefits to metabolic flexibility. Enhancing metabolic flexibility is a gradual process. It requires consistency, patience, and a long-term commitment to healthy lifestyle practices. It's important to consult with a healthcare professional before making significant changes to your diet or exercise routine, especially if you have any underlying health conditions.
If you are interested in learning how to enhance your metabolic flexibility and would like some guidance and support along the way, our nutritionist, Lisa Jubilee is here to assist: info@livingproofnyc.com
