Carbohydrates: What They Are, How They Work - And Why They Are Not Your Enemy
Carbohydrates might be the most talked about, most debated, and most misunderstood macronutrient in nutrition. They've been blamed, restricted, feared, and rehabilitated more times than we can count.
But here's what actually matters: understanding what carbohydrates are, how they work in your body, which ones support your health, and how to eat them in a way that keeps your energy stable and your hormones happy.
This post covers all of it — clearly, practically, and without the noise.
What are carbohydrates, exactly?
Carbohydrates are one of the three macronutrients — alongside protein and fat — that your body uses for energy, structure, and function. They are found in a wide range of foods, from vegetables and wholegrains to fruit, legumes, dairy, and yes, processed foods and sugar.
At their most basic level, carbohydrates are made up of sugar molecules. When you eat carbohydrates, your digestive system breaks them down into glucose — the primary fuel source for your brain, red blood cells, and muscles. Glucose enters your bloodstream, your blood sugar rises, and your pancreas releases insulin to help shuttle that glucose into your cells where it can be used for energy.
This is a completely normal, essential process. Your body is designed to do this. The question is not whether to eat carbohydrates — it is which ones, how much, when, and what to eat them with.
The three types of carbohydrates
Simple carbohydrates are made up of one or two sugar molecules. They are digested quickly, absorbed rapidly into the bloodstream, and cause a fast rise in blood sugar.
Naturally occurring simple sugars:
Fructose — found in fruit and honey
Lactose — found in dairy
Glucose — found naturally in some foods
Added sugars:
Table sugar (sucrose)
High-fructose corn syrup
Agave, rice malt syrup, and most other liquid sweeteners
Sugars added to processed foods, sauces, drinks, and snacks
Naturally occurring sugars — in whole fruit, for example — come packaged with fibre, water, vitamins, and phytonutrients that slow their absorption and buffer their impact on blood sugar. Added sugars arrive with none of that context, which is why they behave very differently in the body.
2. Complex carbohydrates (starches)
Complex carbohydrates are made up of longer chains of sugar molecules, which means they take longer to digest and are absorbed more slowly into the bloodstream. This slower digestion results in a more gradual rise in blood sugar — providing sustained energy rather than a spike and crash.
Whole-food sources of complex carbohydrates:
Oats and rolled oats
Brown rice, wild rice and basmati rice
Quinoa
Sweet potato and regular potato (with skin)
Wholegrain bread and sourdough
Corn and legumes
Pumpkin and root vegetables
The key distinction here is between refined complex carbohydrates and whole complex carbohydrates. When grains are refined — stripped of their bran and germ to create white flour, white rice, or white bread — they lose much of their fibre, vitamins, and minerals. What's left digests almost as quickly as sugar. Wholegrain versions retain their fibre and nutrients, which changes how they behave in the body entirely.
3. Dietary fibre
Fibre is technically a carbohydrate — but one your body cannot digest. Instead of being broken down into glucose, fibre passes through the digestive system largely intact, where it plays a crucial role in gut health, blood sugar regulation, hormone metabolism, and satiety.
There are two types:
Soluble fibre dissolves in water to form a gel-like substance in the gut. It slows digestion, blunts glucose absorption, supports healthy cholesterol levels, and feeds beneficial gut bacteria. Found in oats, legumes, apples, flaxseed, and psyllium husk.
Insoluble fibre adds bulk to stool and keeps things moving through the digestive tract. Critical for bowel regularity and gut health. Found in wholegrains, vegetables, nuts, and seeds.
Most people are not eating nearly enough fibre. The recommendation is 25–30g per day — and the majority of us fall well short of this. Prioritising fibre-rich carbohydrate sources is one of the single most impactful nutrition changes you can make.
What carbohydrates do in your body
Beyond providing energy, carbohydrates play several important roles:
Brain fuel. Glucose is the brain's preferred energy source. Adequate carbohydrate intake supports concentration, memory, mood, and cognitive function. This is why very low carbohydrate diets can cause brain fog, irritability, and difficulty concentrating — particularly in the early stages.
Muscle glycogen. Carbohydrates are stored in the muscles and liver as glycogen — a readily available fuel source for physical activity. Adequate carbohydrate intake supports exercise performance, recovery, and muscle function.
Gut microbiome diversity. Specific types of carbohydrates — particularly prebiotic fibres — feed the beneficial bacteria in your gut. A diverse, well-fed gut microbiome is foundational to immune function, hormone metabolism, mental health, and inflammation regulation.
Hormone production. Carbohydrates play a role in thyroid hormone production and in signalling the brain to regulate reproductive hormones. Very low carbohydrate intake over a long period can suppress thyroid function and disrupt the hypothalamic-pituitary-ovarian (HPO) axis — the signalling pathway that regulates your menstrual cycle.
Protein sparing. When carbohydrate intake is adequate, your body can use dietary protein for its primary jobs — building and repairing tissue, producing enzymes and hormones, and supporting immune function — rather than converting it to glucose for energy.
Understanding the glycaemic index and glycaemic load
Two terms that come up often in nutrition — and are genuinely worth understanding — are the glycaemic index (GI) and the glycaemic load (GL).
Glycaemic Index (GI)
The glycaemic index ranks carbohydrate-containing foods on a scale of 0 to 100 based on how quickly they raise blood sugar compared to pure glucose.
Low GI (55 and below): slow, gradual rise in blood sugar — lentils, oats, most fruits, sweet potato, legumes
Medium GI (56–69): moderate rise — basmati rice, sourdough bread, rolled oats
High GI (70 and above): rapid rise in blood sugar — white bread, white rice, rice cakes, most processed snacks
GI is a useful starting point, but it has limitations. It measures foods in isolation — which is rarely how we actually eat. It also doesn't account for portion size, which is where glycaemic load becomes more useful.
Glycaemic Load (GL)
Glycaemic load takes into account both the GI of a food and the actual amount of carbohydrate in a typical serving. A food can have a high GI but a low GL if you eat a small amount of it — watermelon is a classic example.
Low GL (10 and below): minimal blood sugar impact
Medium GL (11–19): moderate impact
High GL (20 and above): significant blood sugar impact
For most people, focusing on eating whole, minimally processed carbohydrate sources will naturally keep both GI and GL in a healthy range — without needing to calculate anything.
The best carbohydrate sources for everyday eating
Rather than thinking in terms of "allowed" and "not allowed," think about building your carbohydrate choices around foods that offer the most nutritional value alongside their energy.
Vegetables — eat in abundance
Non-starchy vegetables are technically carbohydrates, but they are so low in glucose and so high in fibre, vitamins, minerals, and phytonutrients that they deserve a category of their own. Leafy greens, broccoli, capsicum, zucchini, cauliflower, cucumber, tomatoes, asparagus, spinach — these should form the base of every meal.
Starchy vegetables — sweet potato, pumpkin, corn, peas, beetroot — provide more carbohydrate energy but also significant fibre and micronutrients. They are excellent whole food carbohydrate sources.
Wholegrains
Oats, quinoa, brown rice, barley, buckwheat, and wholegrain sourdough are all excellent sources of complex carbohydrates, fibre, B vitamins, and minerals. These are the carbohydrate staples worth building your meals around.
Legumes and pulses
Lentils, chickpeas, black beans, kidney beans, and edamame are some of the most nutritionally complete foods available — combining complex carbohydrates, plant protein, prebiotic fibre, magnesium, iron, and folate in one package. They digest slowly, keep blood sugar stable, and feed the gut microbiome.
Fruit
Whole fruit provides natural sugars alongside fibre, water, vitamins, and powerful antioxidants. The fibre in whole fruit slows the absorption of fructose, making it behave very differently to added sugar or fruit juice. Berries, apples, kiwi fruit, citrus, and stone fruits are all excellent choices. Lower-sugar fruits like berries and green apple are particularly valuable.
Dairy
Milk, yoghurt, and kefir contain lactose — a naturally occurring milk sugar — but also provide protein, calcium, and in the case of fermented dairy, beneficial live bacteria. Full-fat Greek yoghurt and kefir are among the most nutritionally valuable carbohydrate-containing foods available.
What to pair carbohydrates with
This is one of the most practical — and most impactful — nutrition strategies available. What you eat alongside your carbohydrates matters as much as which carbohydrates you choose.
Protein slows gastric emptying — meaning food moves more slowly from the stomach into the small intestine. This slows glucose absorption and results in a smaller, more gradual rise in blood sugar. Aim for a quality protein source at every meal alongside your carbohydrates — eggs, fish, chicken, Greek yoghurt, legumes, tofu, cottage cheese.
Fat also slows digestion and glucose absorption. Healthy fats — olive oil, avocado, nuts, seeds — added to a carbohydrate-containing meal will blunt the blood sugar response. A drizzle of olive oil over your rice, avocado on your toast, nuts alongside your fruit — these all make a meaningful difference.
Fibre — particularly soluble fibre — forms a viscous gel in the gut that slows carbohydrate digestion. This is why eating vegetables first, or choosing high-fibre carbohydrate sources, is so effective at moderating blood sugar.
The practical rule: never eat carbohydrates alone. Always build a meal or snack around a combination of carbohydrate + protein + fat + fibre. A piece of white toast is a very different metabolic experience to the same toast with eggs, avocado, and spinach.
Meal timing and carbohydrates
When you eat your carbohydrates can be just as relevant as what you eat.
Morning and midday tend to be the best times for your largest carbohydrate servings. Insulin sensitivity is naturally higher in the morning — meaning your cells respond more effectively to insulin and can absorb glucose more efficiently earlier in the day. This is why a carbohydrate-rich breakfast like oats or wholegrain toast is far better tolerated metabolically than the same meal eaten late at night.
Insulin sensitivity naturally declines in the evening. This doesn't mean avoiding carbohydrates at dinner — it means being mindful of portion size and prioritising protein and vegetables as the base of your evening meal, with carbohydrates as a supporting player rather than the star.
Never skip meals to save carbohydrate "allowance." Prolonged gaps without food spike cortisol, crash blood sugar, and drive intense carbohydrate cravings later in the day. Eating consistently — every 3–4 hours — keeps blood sugar stable, cortisol manageable, and cravings under control.
Post-meal movement is one of the most powerful blood sugar tools available. Even a 10-minute walk after eating helps your muscles absorb glucose from the bloodstream without needing additional insulin. This is not about burning calories — it is a direct physiological mechanism that meaningfully reduces post-meal glucose spikes.
Carbohydrates, PCOS/PMOS and your hormones
For women with PCOS or PMOS — Polyendocrine Metabolic Ovarian Syndrome, the recently updated name for the condition formerly known as PCOS — carbohydrate quality and timing are especially important.
Here's why.
The majority of women with PMOS have some degree of insulin resistance — meaning their cells don't respond effectively to insulin's signal. When this happens, the pancreas produces more and more insulin to compensate. Chronically elevated insulin then signals the ovaries to produce excess androgens — male hormones like testosterone — which drive many of the most challenging PMOS symptoms: irregular cycles, acne, scalp hair thinning, facial hair growth, and weight gain around the abdomen.
This means that frequent blood sugar spikes — driven by refined carbohydrates, added sugars, or carbohydrates eaten without protein and fat — directly worsen the hormonal cascade at the root of PMOS.
Importantly, this is not a reason to eliminate carbohydrates. It is a reason to choose carbohydrates wisely and eat them in a way that keeps blood sugar stable. Carbohydrates are not the enemy — poorly composed meals and chronically elevated insulin are.
What the research shows:
Studies consistently demonstrate that women with PCOS/PMOS benefit most from a dietary pattern that:
Prioritises low-GI, high-fibre carbohydrates over refined and processed alternatives
Pairs carbohydrates with adequate protein at every meal
Includes healthy fats to slow glucose absorption
Emphasises gut-supporting foods — 30+ plant foods per week, fermented foods daily — to support the gut microbiome, which directly influences both insulin sensitivity and hormone metabolism
Maintains consistent meal timing to keep blood sugar stable throughout the day
Beyond insulin, carbohydrates also play a role in thyroid hormone production — particularly relevant for women with PCOS/PMOS, who have a higher rate of thyroid dysfunction. Very low carbohydrate diets can suppress the conversion of T4 to T3 (the active thyroid hormone), contributing to fatigue, brain fog, and metabolic slowdown.
And adequate carbohydrate intake supports progesterone production — the hormone that balances oestrogen, supports the luteal phase of the cycle, and is often low in women with PCOS/PMOS. Severely restricting carbohydrates can suppress the HPO axis, reducing the hormonal signalling needed for regular ovulation.
The goal is not fewer carbohydrates. The goal is better carbohydrates, better meals, and better timing.
A simple framework for every day
You don't need to count grams or track glycaemic loads. Here's a simple framework that puts everything above into practice:
Build every meal around this template:
½ your plate — non-starchy vegetables (colour and fibre)
¼ your plate — quality protein (eggs, fish, chicken, legumes, Greek yoghurt)
¼ your plate — complex carbohydrates (oats, quinoa, sweet potato, lentils, sourdough)
A serve of healthy fat (olive oil, avocado, nuts, seeds)
Eat vegetables or protein first — before your carbohydrates. This one change can reduce post-meal blood sugar spikes significantly.
Choose whole over refined wherever possible. Brown over white. Whole fruit over juice. Sourdough over white bread. Oats over cereal.
Snack with purpose. Pair any carbohydrate-containing snack with protein or fat. Apple and almond butter. Oatcakes and cottage cheese. Greek yoghurt and berries. Fruit and a handful of nuts.
Move after meals. Even a gentle 10-minute walk makes a meaningful metabolic difference.
The bottom line
Carbohydrates are not something to fear, eliminate, or feel guilty about. They are an essential macronutrient — a primary fuel source for your brain, muscles, and gut bacteria, and a key player in hormone production and cycle health.
The research does not support removing carbohydrates. It supports choosing them thoughtfully, pairing them strategically, and building meals that keep blood sugar stable and your body well-nourished.
For your hormones, your gut, your energy, and your relationship with food — a balanced, carbohydrate-inclusive diet built around whole foods is both the most evidence-based and the most sustainable approach available.
Eat your oats. Enjoy your sweet potato. Add the lentils. And always, always pair them with protein.
Want to go deeper?
↓ Download the free PCOS/PMOS Starter Guide Workbook Includes a full nutrition section, blood sugar guide, meal planner, and weekly habit tracker - all in one free download.
→ Read next: Think You Might Have PCOS (now called PMOS)? Start Here Everything you need to know about PMOS — symptoms, diagnosis, lab tests, and where to begin.
→ Explore the recipe library Hormonal-friendly recipes built around everything in this post - real food, real flavour, balanced every time.
→ Follow on Instagram Daily nutrition tips, meal ideas, and an honest look at life with PMOS - @monika.b.well
This post is for educational purposes only and is not a substitute for personalised nutrition or medical advice. Always consult a qualified healthcare provider or dietitian for individual guidance.
