Are Carbohydrates Really That Bad? A Nutritionist Explains

Carbohydrates are one of the most hotly debated nutrients in nutrition. Depending on who you ask, they’re either the cornerstone of a healthy diet or the main reason behind weight gain and chronic disease. Carb-loading in endurance sports to the rise of keto and carnivore diets, the conversation has swung wildly between extremes.

The truth, as always, sits somewhere in the middle. Carbs aren’t “good” or “bad” in themselves. What matters is the type you eat, how much, and in what context. For some people, reducing carbs can bring benefits. For others, particularly those who are active, carbs are essential.

Lets get in to the detail and dive into some myths I hear all the time:

What are some common myths about carbohydrates?

Myth 1: Carbohydrates are just empty calories

The idea that carbs are “empty” calories comes from the rise of low-carb diets like Atkins, Dukan, and more recently keto. These approaches lumped all carbs into the same category and painted them as little more than sugar and starch with no nutritional value. When you look around the supermarket and see shelves packed with white bread, pastries, biscuits, and fizzy drinks it’s easy to see where that reputation came from.

But not all carbs belong in the same group. Traditional diets around the world rely heavily on carbohydrates such as rice in Asia, maize in South America, flatbreads and lentils in the Middle East, or pasta and beans in Mediterranean regions. These diets are often linked with better long-term health and longevity. The difference is the quality of the carbs so wholegrains, beans, lentils, fruit, and vegetables that provide fibre, vitamins, minerals, and protective plant compounds alongside carbohydrate.

A large meta-analysis published in BMJ found that people with the highest intakes of wholegrains and fibre had significantly lower risks of heart disease, type 2 diabetes, and bowel cancer [1]. In other words, while some carbs (like sugary drinks) offer very little nutrition, many are actually nutrient packed.

Myth 2: Carbohydrates Make You Fat

This myth took off during the low-carb craze of the early 2000s, when carbs were blamed for spiking insulin which is the hormone that helps move glucose into cells and supposedly “forcing” the body to store fat. On the surface it sounds convincing, but it oversimplifies how metabolism actually works.

The reality is that weight gain comes down to eating more calories than you burn over time. Carbs don’t have unique fat-storing powers. What matters is the type, quality, and context. Refined carbs found in white bread, biscuits, pastries digest quickly, leading to hunger and overeating. In contrast, fibre-rich carbs such as oats, beans, and wholegrains digest slowly, regulate appetite hormones, and keep you fuller for longer.

It also matters what you eat them with. A bowl of pasta tossed with olive oil, vegetables, and beans is handled very differently by the body than pasta baked into an ultra-processed ready meal with added cream, cheese, and flavourings. Ultra-processed foods often combine refined carbs with fats, salt, and additives in a way that makes them easy to overeat. Whole foods, by contrast, deliver fibre, vitamins, and minerals that help with appetite regulation and satiety.

Breakfast is a good example. A slice of white toast with jam may leave you hungry within the hour, while a bowl of porridge topped with nuts and berries provides sustained energy all morning. Both are “carbs,” but they affect appetite in very different ways. A systematic review confirmed this, finding that higher fibre intake is linked with greater satiety and reduced calorie intake across multiple studies [2].

So rather than carbs directly causing weight gain, it’s the refined, low-fibre, ultra-processed types that are most likely to encourage overeating.

Myth 3: Carbohydrates are bad for blood sugar control

Carbs often get demonised because they affect blood sugar. Foods like white bread, sweets, and sugary drinks can cause blood glucose to rise quickly and then fall just as fast. For people with insulin resistance or diabetes, this can be a real issue.

But that doesn’t mean all carbs are bad. Fibre-rich foods like lentils, beans, oats, and fruit release glucose slowly, making them much easier on blood sugar levels. Pairing carbs with protein or healthy fats (for example, wholegrain toast with peanut butter) also slows digestion and moderates blood sugar responses.

For those with type 2 diabetes, reducing refined carbs can be very effective. A meta-analysis of randomised controlled trials found that very low-carb diets improved HbA1c in the short term, though benefits were not consistently superior to other diets over the long term [3]. Another umbrella review reached a similar conclusion that low-carb diets can help initially, but effects tend to level out, and individual responses vary [4].

In practice, focusing on carb quality and portion size usually makes more difference than cutting them out altogether.

Myth 4: Low-carb or keto diets are the best for everyone

Low-carb and ketogenic diets have surged in popularity in recent years. They can work well for weight loss or for managing blood sugar, and some people find them easier to stick with than other diets. But that doesn’t mean they’re the best choice for everyone.

For active people, especially endurance athletes, cutting carbs too low can backfire. Carbs are the body’s preferred fuel for high-intensity exercise, and they play a crucial role in recovery and training adaptations [5]. Sports nutrition guidelines recommend 5–12 g/kg carbohydrate per day for endurance athletes depending on training volume and intensity [6].

The concept of “training low” deliberately restricting carbs in certain sessions to promote fat burning has gained attention. While it does increase fat oxidation, large reviews show it doesn’t consistently improve real-world performance [7]. A recent trial also found that a five-week periodised carb plan did not outperform standard fuelling in trained cyclists [8].

Recovery is another key piece of the puzzle. Rapid glycogen replenishment after hard sessions or competition is critical, and low-carb strategies often make this harder [9]. The most effective approach for most athletes is a flexible one so some lower-carb sessions to build adaptation, but always ensuring adequate carbs are available for demanding training and competition [10].

Myth 5: Fruit has too much sugar

Fruit often gets unfairly criticised for its sugar content, especially by people following very low-carb diets. Yes, fruit contains natural sugars, but it also provides fibre, water, vitamins, minerals, and plant compounds that change the way it’s digested and used by the body.

For example, the fibre in an apple slows the release of glucose into the blood, so eating the fruit is very different from drinking apple juice. Observational studies consistently show that fruit intake is associated with lower risks of obesity, type 2 diabetes, and cardiovascular disease [1].

Myth 6: You don’t need carbohydrates at all

It’s technically true that the body can survive without carbohydrates, using fat and protein for energy instead. The liver can produce glucose through gluconeogenesis, and ketones can act as an alternative fuel.

But “surviving” isn’t the same as thriving. Carbs are the most efficient energy source for the brain and muscles, especially during high-intensity activity. Go too low for too long and you may experience fatigue, poor concentration, and slower recovery.

For older adults or anyone with a reduced appetite, easy-to-digest carb foods like porridge or wholegrain toast can also help maintain energy levels and prevent unintentional weight loss.

When cutting carbs might help

There are situations where reducing carbohydrate intake makes sense:

• Type 2 diabetes: Low-carb diets can improve blood sugar control, particularly in the short term [3,4].
• Weight loss / metabolic syndrome: Meta-analyses show that low-carb diets can produce slightly greater weight loss and reductions in triglycerides and blood pressure over 6–23 months, though the advantage tends to fade over longer periods [11].
• Short-term resets: Some people find low-carb phases useful as a way to “reset” eating habits or kick-start weight loss. The key is to reintroduce healthy carb foods afterwards to ensure long-term balance and adequate fibre.

So, what’s the bottom line?

Carbohydrates are not the enemy. The real issue is the quality and context in which we eat them.

• Limit refined carbs and added sugars.
• Prioritise wholegrains, beans, lentils, fruit, and vegetables.
• Use low-carb diets if they suit your health goals but know they’re not the only answer.
• If you’re active, remember carbs are your best fuel for training, recovery, and performance.

Rather than fearing carbs, think about choosing better ones, eating them in balance, and matching intake to your lifestyle and goals. That’s where the science and real-world health points us towards.

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References

1. Reynolds, A., Mann, J., Cummings, J., Winter, N., Mete, E., & Te Morenga, L. (2019). Carbohydrate quality and human health: a series of systematic reviews and meta-analyses. Lancet (London, England), 393(10170), 434–445. https://doi.org/10.1016/S0140-6736(18)31809-9
2. Clark, M. J., & Slavin, J. L. (2013). The effect of fiber on satiety and food intake: a systematic review. Journal of the American College of Nutrition, 32(3), 200–211. https://doi.org/10.1080/07315724.2013.791194
3. Parry-Strong, A., Wright-McNaughton, M., Weatherall, M., Hall, R. M., Coppell, K. J., Barthow, C., & Krebs, J. D. (2022). Very low carbohydrate (ketogenic) diets in type 2 diabetes: A systematic review and meta-analysis of randomized controlled trials. Diabetes, obesity & metabolism, 24(12), 2431–2442. https://doi.org/10.1111/dom.14837
4. Yan, Y., Asemani, S., Jamilian, P., & Yang, C. (2025). The efficacy of low-carbohydrate diets on glycemic control in type 2 diabetes: a comprehensive overview of meta-analyses of controlled clinical trials. Diabetology & metabolic syndrome, 17(1), 341. https://doi.org/10.1186/s13098-025-01890-7
5. Burke, L. M., & Hawley, J. A. (2018). Swifter, higher, stronger: What’s on the menu?. Science (New York, N.Y.), 362(6416), 781–787. https://doi.org/10.1126/science.aau2093
6. Thomas, D. T., Erdman, K. A., & Burke, L. M. (2016). Position of the Academy of Nutrition and Dietetics, Dietitians of Canada, and the American College of Sports Medicine: Nutrition and Athletic Performance. Journal of the Academy of Nutrition and Dietetics, 116(3), 501–528. https://doi.org/10.1016/j.jand.2015.12.006

Ref continued

1. Gejl, K. D., & Nybo, L. (2021). Performance effects of periodized carbohydrate restriction in endurance trained athletes – a systematic review and meta-analysis. Journal of the International Society of Sports Nutrition, 18(1), 37. https://doi.org/10.1186/s12970-021-00435-3
2. Prieto-Bellver, G., Diaz-Lara, J., Bishop, D. J., Fernández-Sáez, J., Abián-Vicén, J., San-Millan, I., & Santos-Concejero, J. (2024). A Five-Week Periodized Carbohydrate Diet Does Not Improve Maximal Lactate Steady-State Exercise Capacity and Substrate Oxidation in Well-Trained Cyclists compared to a High-Carbohydrate Diet. Nutrients, 16(2), 318. https://doi.org/10.3390/nu16020318
3. Naderi, A., Rothschild, J. A., Santos, H. O., Hamidvand, A., Koozehchian, M. S., Ghazzagh, A., Berjisian, E., & Podlogar, T. (2025). Nutritional Strategies to Improve Post-exercise Recovery and Subsequent Exercise Performance: A Narrative Review. Sports medicine (Auckland, N.Z.), 55(7), 1559–1577. https://doi.org/10.1007/s40279-025-02213-6
4. Podlogar, T., & Wallis, G. A. (2022). New Horizons in Carbohydrate Research and Application for Endurance Athletes. Sports medicine (Auckland, N.Z.), 52(Suppl 1), 5–23. https://doi.org/10.1007/s40279-022-01757-1
5. Lei, L., Huang, J., Zhang, L., Hong, Y., Hui, S., & Yang, J. (2022). Effects of low-carbohydrate diets versus low-fat diets on metabolic risk factors in overweight and obese adults: A meta-analysis of randomized controlled trials. Frontiers in nutrition, 9, 935234. https://doi.org/10.3389/fnut.2022.935234