Why is it that some people struggle to shift the weight even when they’re barely eating anything? And what’s the secret of those who seem to burn fat while simply slumped on the sofa watching Netflix?
Registered dietitian and nutritionist Andrea Calderón believes she has the answer.
The key is “metabolic flexibility” – a fascinating concept that dictates our metabolism’s ability to switch to the most efficient fuel source at any given moment.
“Essentially, metabolic flexibility is our body’s ability to adapt and perform at its best in different situations,” she explains. “It’s when our metabolism knows whether to tap into carbohydrates or make better use of stored fat. This depends on what we’re up to – whether we’re resting or exercising – and which nutrients are available at the time.”
Poor metabolic flexibility doesn’t just leave us feeling drained; it can actually shorten our health span, making it harder to stay fit and well as we age. Meanwhile, good metabolic flexibility is also associated with a lower risk of common modern issues, such as insulin resistance, type 2 diabetes, and high cholesterol.
“And as an added bonus, it helps us achieve a better body composition and makes it much easier to lose fat when we want to,” notes the expert.
“While it’s true that certain changes are inevitable as we get older, many of the issues we blame on age, like gaining fat or losing muscle, aren’t actually the fault of the calendar. Instead, they’re often down to the habits we tend to pick up over the years”
We wanted to know more, so we caught up with Andrea to find out how metabolic flexibility can help us achieve a much higher level of physical and mental well-being, no matter what our age.
For those who haven’t come across the term before, how would you explain metabolic flexibility in a nutshell?
Imagine you’re slumped on the sofa watching Netflix. Ideally, your body should be primarily burning fat for energy at that moment, saving carbohydrates for when it really needs them – like when you’re on the move or pushing yourself physically.
Someone with good metabolic flexibility burns fat while at rest but someone with poor metabolic flexibility might burn very little fat and instead burn carbohydrates, even while sitting still. If they exercise, even at a low intensity, they’ll continue to draw on carbs rather than fat. By the end of a workout, they’ll have burnt less fat than someone else who did the exact same routine but had better metabolic flexibility.
Is it possible to improve metabolic flexibility at any age?
It’s absolutely possible. It is never too late to improve your metabolic health…There are studies showing that even in our 60s or 70s, we can improve our body composition, build muscle, reduce visceral fat and rejuvenate our metabolism. The secret? Sustainable changes: strength training, better nutrition, moving more and prioritising rest. The body always responds.
Age isn’t a life sentence for your metabolism… you can be 50 years old with a metabolic age of 35 if you look after yourself and vice versa. The great thing about metabolic age is that it isn’t fixed. The sooner you start, the better. But if you didn’t start yesterday, don’t worry! Today is still the perfect time to begin
So metabolic flexibility can help us reverse our biological age? What real changes can a person expect to notice in their day-to-day life?
I say it loud and clear: you can absolutely reverse your metabolic age. We can’t take years off our passport, but we can certainly turn back the clock internally. When I talk about reversing biological age, I’m talking about rejuvenating your body from the inside out, not magically getting younger – much as we might wish we could!
© Getty ImagesThis isn’t just something I’ve made up; the science backs it up. Your metabolic age, which is the one that really matters, can significantly improve with the right habits.
“Your metabolism isn’t broken or damaged, and you aren’t stuck with a ‘slow metabolism’ for life”
And the best part is, you really feel the difference. By shifting your habits – eating better, moving more, doing strength training, and prioritising your sleep – you improve your metabolism and feel the benefits almost immediately. Often, this is reflected on the outside too, because how you look on the surface usually follows what’s happening metabolically.
What is the most common mistake we make when trying to lose fat or improve our metabolic health?
The most common mistake is definitely obsessing solely over cutting calories, as if that were some kind of silver bullet. We think, “less in, more out,” and that’s that.
But it simply doesn’t work that way. Some people eat next to nothing and do heaps of cardio, yet don’t see any real progress. Why? Because it’s not just about how much you eat, but how your body handles what you eat.
What role do fats and carbohydrates play in this metabolic flexibility?Do you have cut either of them out to see results?
The trick isn’t to remove things, but to teach the body to use the right fuel at the right time. Think of fats and carbohydrates as two different types of fuel: one is slow-burning and long-lasting, while the other is fast-acting but runs out quickly. The ideal scenario is for your body to know exactly when to switch between them. That, in a nutshell, is metabolic flexibility.
“With the current ‘anti-carb’ trend, carbohydrates have been cast as the villains: the ones causing weight gain, spiking insulin, and stalling our metabolism. But the problem isn’t the rice or the bread; it’s how a body with poor metabolic health handles them”
For example, if you’re dealing with insulin resistance, or if your mitochondria are ‘lazy’ and your muscles aren’t being challenged, you might indeed store more fat if you overdo the carbs. But that’s not the carbohydrate’s fault; it’s a matter of how the body processes it. So no, you don’t have to ditch the carbs or the fats. You just need to improve your metabolic flexibility so your body can choose the best fuel for each moment.
What would you say is the relationship between metabolic flexibility and mood?
It’s a massive link, and it really isn’t talked about enough… When you have good metabolic flexibility, your body manages and distributes energy much more efficiently. In your day-to-day life, that means more sustained energy, fewer “highs and lows,” less of a constant craving for sugar, and of course, a better mood and greater mental clarity.
About the expert:
Andrea Calderón is a Professor of Nutrition and Metabolism at the European University of Madrid (Universidad Europea) and author of the Spanish-language book, The Power of Metabolic Flexibility (El poder de la flexibilidad metabólica).
Read the full article here
