Why metabolic health is shaped by what you do consistently, not occasionally

Golden, crispy roast potatoes; gooey sticky toffee pudding drowning in cream; hearty pies covered in buttery pastry. 

And while these indulgences are delicious, they’re sometimes accompanied by feelings of guilt. Instead of enjoying time with loved ones, you may be doing the mental math on how many calories are on your plate. 

However, our bodies are good at managing slightly outside-the-norm behaviour. Short periods of less healthy eating—like those around the holidays—aren’t likely to have a significant impact on your health, especially if you’re metabolically healthy.

Let’s unpack what being metabolically healthy actually means, how it impacts you, and steps you can take to improve it.

What does it mean to be metabolically healthy?

The concept of ‘metabolic health’ can feel like a bit of a black box. We might scoff at our friend who downs pizzas and sweets—without putting on an ounce—and grumble that they just have a ‘fast metabolism.’ But what does that actually mean?

While metabolic health is tied to weight, it’s not exclusively so. It isn’t a strictly defined term, but it essentially explains your body’s ability to turn food into energy efficiently. When these systems stop working as usual, hallmarks of metabolic disease (like elevated blood sugar and high blood pressure) show up.

Metabolic flexibility, which is your body’s ability to adjust its fuel use depending on what you’ve eaten and whether you’re in a fed or fasted state, is one component of your metabolic health. In other words, it can burn glucose after meals, and shift smoothly to burning fat when carbohydrates are scarce. Your body can also choose which fuel to use depending on what you’ve eaten—for example, using more glucose after a carb-rich meal.

Think of it like switching between the petrol and battery in a hybrid car—when it can swap fuel transitions easily, the car runs smoothly and efficiently.

On the flipside, metabolic inflexibility can occur alongside obesity, insulin resistance (IR), type 2 diabetes, and metabolic syndrome. This can push your body into a state of relying upon carbohydrates for energy. 

After eating, your body produces insulin, which gives your cells the green light to absorb glucose. But if you’re metabolically inflexible, this can become impaired. Over time, it can lead to higher blood glucose levels that contribute to IR and the development of type 2 diabetes.

What happens when you eat an indulgent meal?

We’ve established that metabolic flexibility is important—but how does it work when you sit down to a plate of turkey and roast potatoes?

After you eat, your body breaks down your food: carbohydrates become glucose, and fats become fatty acids. The rise in glucose triggers insulin, which shifts your energy source to carbohydrates and turns off fat burning.

In metabolically flexible people, this transition is smooth. Their muscles absorb glucose efficiently, storing the excess as glycogen, and fat is tucked away in normal fat cells for later use. A few hours later, they transition back to fat-burning mode and use the stored fat as fuel.

But in less metabolically flexible (i.e. insulin resistant) people, the process is slower and less efficient. Their muscles don’t respond as well to insulin, so glucose isn’t cleared as effectively, leaving insulin levels higher for longer. Fat burning is suppressed, so more of the emal’s fat is stored where it shouldn’t be, like in the liver or as visceral fat around the organs.

However, it’s important to remember that your body is good at dealing with one-offs like holiday treats and celebratory meals. The impacts are largely temporary, and your body will return to its usual baseline when you return to normal eating habits.

You are what you eat consistently, not sometimes

Think of metabolic flexibility like resilience. It’s something that’s continually built and maintained over time, and it means your body is better able to handle occasional high-calorie, high-fat meals. Imagine squeezing the soap out of a sponge and it returning to shape.

What shapes your metabolism is what you do most of the time, not sometimes. Keeping your metabolic health in check means avoiding chronic overconsumption of high-calorie, indulgent meals, as this can lead to IR and weight gain over time.

Most research on metabolic flexibility examines short bursts of eating or fasting under lab conditions. Real life is messier, so we don’t know exactly where the line is between harmless indulgence and habits that affect metabolic health. 

What we do know is that occasional rich meals aren’t a problem for most people. Paying attention to how you feel and tracking key health markers over time can give you a sense of your own metabolic resilience. 

How to know if you’re metabolically flexible

There’s no single metric that defines metabolic flexibility. You can assess it through a constellation of different biomarkers that paint a broader picture of your metabolic health.

Body measurements are an easy first step. Grab a tape measure if you have one handy, and take a measurement of your waist circumference. You can use this to determine your waist-to-height ratio, which is a strong predictor of metabolic health and can identify if you have too much visceral fat. The NHS provides a handy calculator here.

Testing your blood markers is the next step. Key indicators include:

• HbA1c: This measures your average blood glucose control over the last three months and gives you information about your diabetes risk.
• Advanced lipid profile: This gives a detailed look at the fats and the proteins that transport fats in your blood, providing a more advanced insight into your risk of heart disease.
• High sensitivity CRP: This test can tell you if you have low-grade chronic inflammation, a key risk factor for heart disease. 

Another biomarker worth considering is the triglyceride to HDL ratio. While it’s often used to evaluate heart disease risk, it can also be used as a marker of insulin resistance. The Thriva team has been working on validating reference ranges to use this biomarker for IR, and it’ll be available to our users soon.

Yes, you can increase your metabolic flexibility

Your metabolic health is something you have the power to influence with your everyday actions. And while online health advice can often make this seem complicated, the evidence on metabolic flexibility is remarkably simple, and it largely comes down to movement and eating habits.

Movement

According to research, regular exercise can improve metabolic flexibility, with particular benefits from high-intensity exercise. There’s also evidence that aerobic exercise like running and jogging, as well as weight training, is associated with a healthier cardiometabolic profile than other forms of exercise. 

Aerobic exercise increases the number of new mitochondria (i.e. the powerhouse of the cell), as well as making them more efficient. This improves your body’s ability to burn fat and switch between fuel sources. It also increases insulin sensitivity.

Additionally, weight training improves metabolic flexibility by increasing muscle mass, creating a larger ‘sink’ to absorb glucose after meals. While it works slightly differently to aerobic exercise, it’s complementary.

Another evidence-backed strategy to improve your metabolic flexibility is reducing sedentary time. Try adding short walk breaks, stretches, or standing time to your work day, and consider adding a short walk after dinner.

Eating habits

Your usual habits are what shape your metabolic health. Focus on key pillars, including:

• Avoid chronic over-nutrition: This means you won’t be constantly overwhelming your system.
• Space your meals out: This doesn’t mean fasting—it means allowing time between your meals and avoiding frequent snacking. By allowing your insulin levels to drop, you give your body a chance to switch to fat-burning mode.
• Choose good foods: Specifically, we’re talking about foods that support stable glucose levels. Think high-fibre, nutrient-dense, minimally processed options such as fruits and vegetables, nuts, seeds, beans, legumes, and whole grains.

Takeaway

Your body is smart, and it knows how to deal with short periods of less healthy eating. Your metabolic health is shaped by what you do consistently, not occasionally.

You can get an understanding of your metabolic health by testing biomarkers like your HbA1c and lipids. Later this month, Thriva will be releasing a new dashboard that consolidates all your metrics—including biomarkers, activity tracking, and anthropometric measurements—in one place. It’ll help you get a clear picture of different areas of your health, including your metabolic health.

While it’s important to have a foundation of healthy habits, life is meant to be lived—and that means enjoying December without stressing about food.

Disclaimer: This information is for general educational purposes only and isn’t a substitute for professional medical advice, diagnosis, or treatment. Always speak with a qualified healthcare professional first if you have concerns about your health.