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Ever wonder why skipping meals feels easy for some but leaves others feeling shaky or tired when doing the same thing? One reason for this difference is known as metabolic flexibility. This is your body’s ability to switch between burning carbohydrates and fat for energy.  

A metabolically flexible body uses glucose after meals to prevent spikes in blood sugar. Later, between meals or overnight, it shifts naturally to burning stored fat. This smooth transition helps maintain steady energy levels and supports healthy metabolic function.

Why metabolic flexibility matters
Our ancestors thrived on this system during feast-and-famine cycles. Their survival required a metabolism that could rapidly store fuel as fat when food was plentiful, then burn that fat when food was scarce, essentially enabling them to be active even when they hadn’t eaten in a while. Today, however, constant grazing, larger portions, frequent snacking and less physical activity mean many of us rarely enter a true fasted state.

Over time, this can reduce the body’s ability to switch between fuels, contributing to:

• Persistent fatigue
• Weight gain
• Blood sugar swings
• Increased hunger and cravings
• Reduced insulin sensitivity

Metabolic inflexibility is also linked to conditions such as obesity, type 2 diabetes, metabolic syndrome, and fatty liver disease.

The good news? Metabolic flexibility can be rebuilt, and the benefits are significant. 

Why it matters
When your body becomes more efficient at switching between fuel sources, you experience more: 

• Stable energy: No more sugar crashes.
• Better fat burning: Your body uses stored fat efficiently.
• Improved blood sugar control: Lower risk of chronic disease.
• Enhanced metabolic health: More energy, less fat storage.

How to improve your metabolic flexibility

• Move your body regularly: Exercise trains your muscles to burn carbs first, then fat. Just 10 days of aerobic activity can improve insulin sensitivity and fat metabolism. Have you ever found that after working out for a few weeks, you’re not thinking about snacks as heavily and your energy feels more consistent? That’s a signal that your body is adapting to refuel itself more efficiently. Any activity that raises your heart rate.

o Brisk walking
o Cycling
o Running
o Aerobic workouts
o Any movement that raises your heart rate

Extend the time between meals: Intermittent fasting has been shown to improve insulin sensitivity, even when overall weight loss is only modest and isn’t necessarily different from that achieved by a kilojoule daily restriction. It also flips on a “maintenance mode” within your cells, triggering internal clean-up and repair processes that improve as well as fine-tune how well your cells work. 
It can be as easy as lengthening your overnight fast, for example:

• 12-hour fast: Stop eating at 19:00, have breakfast at 07:00
• 14 to 16-hour fast: Shorten your eating window for deeper metabolic benefits

When the liver’s stored glucose begins to run out, the body switches to burning fat and producing ketones, an alternative fuel source for the brain and muscles.

Research shows that intermittent fasting can improve insulin sensitivity and activate natural cellular repair processes, even when weight loss is modest.

• Align meals with your body’s internal clock

Time your meals. Your metabolism follows a natural day-night rhythm.
Eat earlier in the day when your metabolism is strongest. Avoid late-night snacking. Some people engage in what is referred to as time-restricted eating, meaning they eat only during a specific number of hours each day, such as within an 8- or 10-hour window, and fast the rest of the time. Research shows that this approach may have a positive impact on your metabolic health. 

Time-restricted eating, such as consuming all meals within an 8- to 10-hour window, has been shown to improve:

• Blood sugar control
• Energy levels
• Appetite regulation

For example, adults with prediabetes who ate all meals earlier in an 8-hour window improved their blood sugar levels without reducing total kilojoule intake. Providing time to your body and its metabolism, sailing on “fewer cylinders” between meals, may equip you with the ability to work toward fuel-switching once again. This helps you become more metabolically flexible over time. 

• Support healthy daily habits
• Consistency in small habits makes a meaningful difference.

You can support metabolic flexibility by:

• Prioritising quality sleep
• Reducing unnecessary snacking
• Staying active throughout the day
• Allowing your body time between meals to use stored energy

Over time, these habits help your metabolism become more responsive and efficient.

The science behind it
Exercise boosts mitochondria, your cells’ power plants and improves insulin sensitivity. Fasting depletes stored glucose, forcing your body to burn fat and produce ketones, an alternative fuel for your brain and muscles. These strategies help your metabolism “switch gears” smoothly, like a well-tuned hybrid engine.

The result? More stable energy, improved metabolic health and a body that feels better equipped to meet the demands of daily life.

Bestmed Tip: Start small. Add an hour to your overnight fast or take a brisk walk today. Your metabolism will thank you and so will your energy levels.