Metabolic Flexibility

April 21

Metabolic Flexibility

If you need to eat every few hours to prevent getting hangry, read on because today we are talking about metabolic flexibility.

Humans are innately metabolically flexible, which means that we are designed to burn both carbs (glucose & glycogen) and fats (dietary & stored) for energy. In fact glucose is not the preferred fuel of muscle cells under normal human resting metabolic conditions or even under most normal human movement patterns (exercise), fat is. It’s why carbs are ‘non essential’ and we can make what the body needs from fats and protein through gluconeogenesis.


Before food became as accessible to us as it is now, we were metabolically flexible by necessity as some days there was plenty of food and other days there weren’t. However now, since we have such quick and easy access to food and snacks and for many a diet high in carbohydrates, our bodies tend to look more for carbs for energy & struggle to switch into burning fat stores. When we don’t have access to these carbs we tend to get carb cravings, have mid-afternoon slumps in energy, feel weak, get “hangry” & are easily distracted until we get our carb “fix”.

However, if you build your metabolic flexibility, you don’t have as heavy a reliance on carbs & can more easily burn fat for energy. Burning mostly carbs is limiting because carbs only contain 4 calories of energy per gram, our carbohydrate stores only contain ~2000 calories of energy plus burning carbs creates more metabolic stress whereas fat contains 9 calories per gram, our fat stores are virtually unlimited and cells burning fat are way better off as the cells are not under as much metabolic stress.


If you can tap into your fat stores, then your body stops constantly searching for quick sources of energy from carbs which can lead to metabolic disorders such as insulin resistance and diabetes (check out our insulin post). Improving fat burning capability is also beneficial for endurance athletes because if you can tap into your fat stores you don’t need to rely on ingesting so many carbs for energy during a race. Ingesting lots of carbs via gels and bars often leads to a debilitating upset stomach which effects performance but not ingesting them when you’re not fat adapted also results in the dreaded “bonk” or “hitting the wall” because you just run out of energy.


There are a few ways to improve your metabolic flexibility:

  1. Adopt a lower carb or where appropriate a ketogenic diet
  2. Incorporate intermittent fasting into your routine

At Sip Kitchen we develop our offering using this philosophy, providing whole food higher fat and lower carb options, whole food good quality high carb options, all overlaid with nutrient density considerations as well. We have also developed the Longevity Fasting Diet with The Boyd Clinic which is lower carb, super low in sugar and high healthy fat which also gets you into fat burning by being low in calories.