This series starts with carbohydrates, but not with the myths you already know are wrong. These six are the “healthy” rules: the ones that careful, well-informed people follow. For each one, here’s where it comes from, what the research shows, and what that means on your plate.
This series is general, evidence-based education, not individual advice. I’m a movement teacher with nutrition training, not a nutritionist. If you have a medical condition, or a complicated relationship with food, please work with a professional.First: why you need carbs at all
Carbohydrates come as sugars (glucose, fructose, lactose, sucrose), starches (long chains of glucose in grains, potatoes and legumes) and fibre (the part your enzymes can’t digest, which feeds your gut bacteria instead). Before we take apart any myths, here’s what they actually do for you:
Your brain runs on glucose. It uses roughly 100–120 g a day. That figure is the basis of the official recommended minimum of 130 g of carbohydrate a day for adults (Institute of Medicine, 2005). Your body can make some glucose from other sources, but that’s a back-up system, not a design.
Your muscles rely on them as intensity rises. Carbohydrate is stored as glycogen in muscles and liver. At gentle intensities you burn a mix of fat and carbohydrate; the harder you work, the more you depend on glycogen, because it releases energy faster. A strong reformer session, a run, a jump class all draw on it.
They’re your only source of fibre. Fibre only exists in carbohydrate foods: grains, legumes, fruit, vegetables, nuts and seeds. Cutting carbohydrate cuts the food your gut bacteria live on.
They protect your protein. When carbohydrate is scarce, your body breaks down amino acids, including from muscle, to make the glucose it needs. Enough carbohydrate lets protein do its own job: repair and adaptation.
Your hormones notice. Low carbohydrate availability adds to the effects of under-fuelling on cycles, thyroid hormones and bone (Mountjoy et al., 2023). More on that in myth 5.
Carbs aren’t a treat you earn. They’re infrastructure.
Myth 1 · “Fruit has too much sugar”
Where it comes from: fruit contains fructose, and very high intakes of fructose, mostly from sweetened drinks and processed foods, are linked to metabolic problems. So fruit gets lumped in.
What the evidence says: a study following more than 187,000 adults across three large cohorts found that people who ate more whole fruit, especially blueberries, grapes and apples, had a lower risk of type 2 diabetes. People who drank more fruit juice had a higher risk (Muraki et al., 2013). A large meta-analysis also linked higher fruit and vegetable intake with lower risk of heart disease, stroke and early death (Aune et al., 2017).
Why the difference? The sugar is the same, but the package isn’t. Whole fruit brings fibre and water, needs chewing and takes time to eat, so the sugar arrives slowly and in modest amounts. Juice removes most of that. A glass of orange juice can contain the sugar of three or four oranges, gone in a few seconds.
On your plate: eat the fruit. Treat juice, smoothies with lots of fruit, and dried fruit by the handful more like sweets than like fruit.
Myth 2 · “Honey, agave and coconut sugar are the healthy sugars”
Where it comes from: they’re less processed, sound natural, and are marketed with words like “unrefined” or “low GI”.
What the evidence says: the World Health Organization classes honey, syrups and fruit juices together with table sugar as free sugars, the ones worth keeping low, ideally under 10% of daily energy, mainly for dental and metabolic health (WHO, 2015). Chemically they’re close cousins. Coconut sugar is mostly sucrose, the same molecule as white sugar. Agave syrup is mostly fructose, which is why it has a low glycaemic index; fructose doesn’t raise blood glucose much, but it’s processed by the liver, and that’s exactly the type of sugar people worry about. Honey does contain small amounts of antioxidants and other compounds, but in the amounts you’d eat, they’re trivial next to what you get from a piece of fruit.
On your plate: choose the one you like the taste of, and use it as what it is: sugar. There’s no need to pay extra for a “healthier” version.
Myth 3 · “Gluten-free is the cleaner choice”
Where it comes from: some people genuinely need to avoid gluten, and many people feel better when they cut out bread and pastries. It’s easy to conclude that gluten was the problem.
What the evidence says: about 1% of people have coeliac disease, and for them, strict gluten avoidance is essential. Others have a diagnosed sensitivity. For everyone else, a study following more than 100,000 health professionals for over 25 years found no link between gluten intake and heart disease. The authors warned that avoiding gluten may lead to eating fewer whole grains, which are protective (Lebwohl et al., 2017). A comparison of packaged products found gluten-free versions were often lower in fibre and protein, and more expensive (Missbach et al., 2015).
As for feeling better: cutting gluten usually means cutting a lot of ultra-processed food, and that change alone can explain it. Wheat is also high in certain fermentable carbohydrates (FODMAPs) that can cause bloating in some people, which has nothing to do with gluten itself.
If you suspect a problem with gluten, get tested before cutting it out. Coeliac tests need you to be eating gluten to be accurate.
On your plate: unless you have a diagnosis, whole-wheat bread, pasta, broa and oats are some of the most protective foods available.
Myth 4 · “Low glycaemic index means healthy”
Where it comes from: the glycaemic index (GI) ranks foods by how quickly they raise blood glucose. Lower sounds better, and it’s now printed on packaging and in apps.
What the evidence says: GI is a useful lab measure, but a poor guide to how healthy a food is. It’s measured by eating a fixed amount of carbohydrate from a single food, alone, after a fast. In real life:
• Fat lowers GI. That’s why crisps and chips score lower than boiled potatoes, and ice cream lower than watermelon.
• Portion matters. Watermelon has a high GI, but a slice has so little carbohydrate that its real effect is small. That’s what “glycaemic load” tries to capture.
• Your plate changes it. Eating carbohydrate with protein, fat, fibre or something acidic (like a salad with vinegar) slows the rise. Cooking and cooling potatoes, rice or pasta turns some starch into resistant starch, which also lowers the response.
• Your body changes it. When researchers continuously measured glucose in 800 people, the same foods produced very different responses in different people, partly linked to their gut bacteria (Zeevi et al., 2015).
On your plate: think in meals, not single foods. Fibre-rich carbohydrate with protein and vegetables does more than chasing low-GI labels.
Myth 5 · “Training fasted and cutting carbs is better for women’s hormones”
Where it comes from: social media trends promising “hormone balance” through fasting, low-carb eating and fasted workouts, often aimed specifically at women.
What the evidence says: the research points the other way. Your reproductive hormones respond to how much energy is available after training. In a controlled study, when energy availability in regularly menstruating women dropped below a certain level, the pulses of luteinising hormone, the signal that drives ovulation, were disrupted within days (Loucks & Thuma, 2003). The International Olympic Committee’s consensus on Relative Energy Deficiency in Sport (REDs) describes how chronic under-fuelling affects cycles, bone, metabolism, mood and performance, and notes that low carbohydrate availability in particular adds to some of these effects (Mountjoy et al., 2023). In elite athletes, even a few weeks of very-low-carbohydrate eating increased markers of bone breakdown during exercise (Heikura et al., 2020).
That doesn’t mean a fasted 7am class is harmful. For a moderate, hour-long session, training before breakfast is fine if you feel good (more on that in our “Before class” post). The problem is the pattern: training regularly on an empty tank, skipping carbohydrates, and not making it up later.
Signs worth paying attention to: irregular or missing periods, constant tiredness, feeling cold, frequent injuries, poor recovery or loss of motivation to train. If any of these sound familiar, see your doctor.
Myth 6 · “No carbs after 6pm”
Where it comes from: a mix of diet-culture rules and a real piece of science: your body’s internal clock does change how you handle glucose across the day.
What the evidence says: that science is real but often misread. In a carefully controlled study, the same meal produced a higher blood glucose response in the evening than in the morning, partly because of the circadian system itself (Morris et al., 2015). But this applies to any meal eaten late, not specifically to carbohydrate, and it changes gradually through the evening. There’s nothing special about 6pm. In Portugal, where dinner is often at 8 or 9pm, the rule would simply mean never eating carbs at dinner.
Two things argue against cutting them, especially if you move in the evening:
• Recovery. After training, muscles refill their glycogen fastest when carbohydrate arrives soon after. In a classic study, delaying carbohydrate by two hours after exercise roughly halved the rate of glycogen storage in that period (Ivy et al., 1988). After an evening class, dinner is your recovery meal, and it shapes how ready you are tomorrow.
• Sleep. In a small study, a carbohydrate-rich dinner eaten four hours before bed helped people fall asleep faster than a lower-glycaemic version of the same meal (Afaghi et al., 2007). It’s one study, so don’t treat it as a sleep trick, but it’s the opposite of what the 6pm rule suggests. Many people who cut carbs at dinner also report waking hungry or sleeping worse.
What does make sense: avoid very large meals right before bed, leave two to three hours between dinner and sleep when you can, and build dinner like any other meal: vegetables, protein and a fibre-rich carbohydrate. The clock matters a little. The carbs aren’t the problem.
So what actually matters?
Three questions instead of rules
Fibre: is most of my carbohydrate coming from whole grains, legumes, fruit, vegetables and potatoes?
Form: am I eating foods whole, rather than as juices, syrups and ultra-processed versions?
Enough: am I eating enough to support the training I do?
The traditional Portuguese table already does this well: sopa with legumes, pão de mistura or broa, rice with beans, potatoes, fruit after meals. None of it needs a rule.
Next in the series: protein, and why your training is quietly asking for more of it.
References1. Muraki I et al. Fruit consumption and risk of type 2 diabetes: results from three prospective longitudinal cohort studies. BMJ. 2013;347:f5001.2. Aune D et al. Fruit and vegetable intake and the risk of cardiovascular disease, total cancer and all-cause mortality: a systematic review and dose-response meta-analysis. Int J Epidemiol. 2017;46(3):1029–1056.3. World Health Organization. Guideline: sugars intake for adults and children. Geneva: WHO; 2015.4. Lebwohl B et al. Long term gluten consumption in adults without celiac disease and risk of coronary heart disease: prospective cohort study. BMJ. 2017;357:j1892.5. Missbach B et al. Gluten-free food database: the nutritional quality and cost of packaged gluten-free foods. PeerJ. 2015;3:e1337.6. Zeevi D et al. Personalized nutrition by prediction of glycemic responses. Cell. 2015;163(5):1079–1094.7. Loucks AB, Thuma JR. Luteinizing hormone pulsatility is disrupted at a threshold of energy availability in regularly menstruating women. J Clin Endocrinol Metab. 2003;88(1):297–311.8. Mountjoy M et al. 2023 International Olympic Committee’s (IOC) consensus statement on Relative Energy Deficiency in Sport (REDs). Br J Sports Med. 2023;57(17):1073–1097.9. Heikura IA et al. A short-term ketogenic diet impairs markers of bone health in response to exercise. Front Endocrinol. 2020;10:880.10. Morris CJ et al. Endogenous circadian system and circadian misalignment impact glucose tolerance via separate mechanisms in humans. Proc Natl Acad Sci USA. 2015;112(17):E2225–E2234.11. Afaghi A, O’Connor H, Chow CM. High-glycemic-index carbohydrate meals shorten sleep onset. Am J Clin Nutr. 2007;85(2):426–430.12. Ivy JL et al. Muscle glycogen synthesis after exercise: effect of time of carbohydrate ingestion. J Appl Physiol. 1988;64(4):1480–1485.13. Institute of Medicine. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. Washington DC: National Academies Press; 2005.I’m a Pilates teacher, not a nutritionist or doctor. This content is for general education only and isn’t personal medical or nutritional advice. Before making changes to your diet or taking supplements, please talk to your doctor or a registered nutritionist, especially if you have a health condition, take medication or are pregnant.
