What does it actually mean to have a healthy metabolism?

When we talk about metabolism, we tend to describe it as either fast or slow. We talk about boosting it, speeding it up or blame it when our body doesn’t seem to respond the way we expect. But there’s another way to think about metabolic health: how well can your body adapt?

Your body has access to two fuel sources, glucose and fat. At any given moment, it’s using a mixture of both to produce the energy required for everything from breathing and thinking to walking and exercising. The ability to adjust which fuels you use according to what’s available and what your body needs is known as metabolic flexibility.

Your metabolism is designed to switch gears

After you eat a meal containing carbohydrates, glucose becomes available and your body increases its use of glucose for energy. Some of what isn’t immediately required can also be stored as glycogen in your liver and muscles for later. If you don’t eat food that provides a direct source of glucose, the body will convert proteins into glucose to meet these needs. As time passes between meals, your body shifts towards using more stored fuels – glycogen (to provide glucose) and including fat.

This ability to move between fuel sources is normal physiology. Different tissues have different energy requirements and those requirements change throughout the day depending on whether you’ve just eaten, you’re sleeping, exercising or going about your day. A metabolically flexible body can adapt accordingly.

What does insulin have to do with it?

Quite a lot. Insulin is a hormone produced by your pancreas. One of its key jobs is helping glucose move from your bloodstream into cells, where it can be used for energy or stored for later. When your cells respond well to insulin your body can manage this process efficiently. When they become less responsive, your pancreas needs to produce increasing amounts of insulin to achieve the same effect. This is known as insulin resistance.

Insulin resistance and metabolic inflexibility are closely intertwined, but it’s important not to think of metabolic flexibility as an on/off switch. It’s a dynamic aspect of metabolism influenced by numerous factors, from physical activity and muscle mass to sleep, nutrition, light and hormonal signals.

Insulin isn’t the only hormone in the conversation

Your sex hormones interact with your metabolism too and metabolic health influences the hormonal environment – the relationship goes both ways. One clear example is Polyendocrine Metabolic Ovarian Syndrome (PMOS), the new name for what was previously known as Polycystic Ovary Syndrome (PCOS). The name was changed this year to better reflect what we now understand about the condition: it isn’t simply an ovarian issue, but a complex endocrine and metabolic condition. Insulin resistance is commonly present in PMOS, and can interact with ovarian hormone production, pushing androgens to excess, which in turn can worsen insulin resistance. Support for those with this condition often begins with a big focus on addressing the insulin resistance.

Stress changes how your body uses fuel too

Food tends to dominate conversations about metabolic health, but your nervous system and adrenal stress hormone response belongs in the conversation as well. When your brain perceives a threat, your body needs energy quickly. Stress hormones such as adrenaline and cortisol help make glucose more readily available in your bloodstream so you have the fuel to escape from the danger your body perceives it is in. If you genuinely need to run away, this is an incredibly useful survival mechanism.

The body, however, can initiate a stress response to psychological threats too. A perception of a ‘relentless’ workload, financial worries, conflict, caffeine, a lack of sleep or simply a mind that rarely switches off can all contribute to repeated activation of your stress response. This doesn’t mean stress automatically makes someone metabolically inflexible. Metabolic health is far more complex than that. Yet, chronic stress can influence the fuel your body perceives is safe and appropriate for you to use (more glucose than fat, for example), as well as glucose regulation itself, appetite, sleep and other behaviours and processes that matter for metabolic health. Which is why focusing exclusively on food misses part of the picture. Our founder, Dr Libby wrote about these concepts in two of her books: Accidentally Overweight and Rushing Woman’s Syndrome.

Your liver and muscles matter more than you might realise

Your liver is one of the body’s major metabolic organs. After you eat, it can store glucose as glycogen. Between meals, it helps maintain blood glucose levels by making stored glucose available and, when necessary, producing glucose from other substrates. The liver can also get the message from substances in some ultra-processed foods that it needs to switch on its own fat production. The accumulation of fat in the liver is another contributor to insulin resistance so preventing or addressing this often requires a focus on liver support.

Skeletal muscle is another major player. It accounts for a substantial proportion of glucose uptake following a meal and physical activity increases the muscles’ demand for energy. This is one reason movement matters so much for metabolic health. And it doesn't need to mean punishing workouts. Walking, lifting weights and other forms of resistance training can all contribute to better metabolic function.

Do you need to fast or go keto to become metabolically flexible?

No. Ketogenic diets and fasting can alter the fuels your body uses, but they aren't prerequisites for metabolic flexibility. Your body inherently has the machinery to use both glucose and fat. The goal isn't to force it to burn fat all the time. In fact, that would miss the point of metabolic flexibility entirely. It’s about being able to adapt.

For many people, a more sustainable place to start is with the everyday foundations that support metabolic health rather than adopting an extreme dietary approach that may be difficult to sustain or compromise overall nourishment if it isn't carefully planned.

How can you support metabolic flexibility?

Eat mostly whole foods

Build meals around vegetables, quality sources of protein, nourishing fats and whole food or minimally processed carbohydrate sources, while reducing your reliance on highly refined and ultra-processed foods. Organic Daily Greens & Reds is made from certified organic whole foods and can be used alongside a varied diet to broaden your nutritional intake. People who take it daily have shared that it’s also incredibly helpful at making sugar cravings a thing of the past.

Move your body regularly

Walking matters. So does maintaining and building muscle through resistance training. Muscle supports strength, mobility, balance, bone density and metabolic health, helping the body use glucose more effectively and remain resilient as we age.

Prioritise sleep

Insufficient and disrupted sleep can affect glucose metabolism and insulin sensitivity, so sleep is part of metabolic health too. Poor sleep may also influence appetite-regulating hormones like leptin and ghrelin, the stress response, and food choices, making it harder for the body to maintain stable energy and blood sugar levels. Aim for a consistent sleep schedule and a restful environment where possible.

Support your nervous system

If your body spends a large portion of the day receiving messages that it’s under threat, consider where you can reduce the load. Something as simple as slowing your breathing can help shift your nervous system state. For additional support, Calm Restore offers relief for a busy mind, and from both acute and chronic stress.

Consider your overall nutrient intake

Your metabolism relies on vitamins and minerals to carry out the enormous number of biochemical reactions involved in producing and using energy. Magnesium, for example, plays a crucial role in supporting healthy insulin sensitivity by acting as an essential cofactor for glucose metabolism and insulin receptor signaling. Plus, it contributes to healthy energy metabolism. Other nutrients are involved too: B vitamins help enzymes release energy from carbohydrates, fats, and proteins; iron supports oxygen transport and energy production; and iron, zinc, selenium, and iodine contribute to processes involved in thyroid hormone production and function, antioxidant protection, and cellular metabolism. This highlights the importance of a varied and diverse way of eating to ensure you are obtaining all of the nutrients you need on a daily basis.