Is a low-carb diet right for you?
From Atkins to keto, low-carb food regimes are some of the most searched-for diets online. They claim to aid weight loss, reduce blood sugar levels and even reverse type 2 diabetes. But is cutting carbs really a healthy diet to follow? What are carbohydrates? Carbohydrates (carbs) are one of three macronutrients found in food and drink, the other two being protein and fat. Our bodies break carbohydrates down into glucose, which provides energy for our bodies and brains. “Healthy carbohydrates are essential for good brain health,” says dietitian Tai Ibitoye. “They are great for your gut and provide our body with a range of vitamins and minerals like calcium, iron, B vitamins and fibre.” Are all carbohydrates the same? Carbs can be divided into ‘simple’ (also known as ‘refined’), and ‘complex’. As their names suggest, simple carbs have simple molecular structures, whilst complex carbs have more complex ones. This is important because of the way our bodies react to carbohydrates when we digest them. Simple carbs are sugars – which include lactose in dairy products, fructose in fruit and ‘free’ sugars in sweets, sugary drinks and desserts. When we consume them, their simple molecular structure mean they break down quickly – causing spikes in our blood sugar and our pancreas to release insulin. Research suggests consuming too much of these is associated with insulin resistance, which can lead to health problems over time, including obesity, Type 2 diabetes and high blood pressure. The refined carbohydrates in high-sugar food and drink break down quickly in your gut and cause spikes in your blood sugar. Complex carbs on the other hand, are starchy carbohydrates such as pasta, bread and rice. There are fibre-rich options including wholegrain versions of pasta, rice and bread, as well as some vegetables and fruit and pulses. Their complex molecular structures means they take longer to digest, causing gradual rises in blood sugar and insulin release. This is better for your body, and will also keep you fuller for longer. What is a low-carb diet? A low-carb diet is one that restricts the consumption of carb-heavy food and drinks (such as juices, beer and sugary sodas), on the basis you replace them with other nutrient-dense ingredients. With less carbs for energy, the body is forced to turn to its fat stores and convert fat into energy instead. Dr David Unwin, the vice chair of the advisory board for the Public Health Collaboration charity, is well-known for pioneering a low-carb approach with his patients at his GP surgery in Southport, Merseyside: “We are a dual-fuel engine, adapted to burn fat or sugar," he says. Dr Unwin argues: "Weight-for-weight, fat supplies more energy than carbohydrates, and many of us have an overabundance of personal fat reserves we would be better to burn.” The amount of carbs you eat on a low-carb plan depends on the diet you follow – for example, the ketogenic diet suggests people eat just 20-50g carbs a day. “Officially for research purposes [a low-carb diet] is less than 130g of carbohydrate per day, but for many of my patients it means just cutting back on sugar and the starchy carbs like bread, cereals or potatoes that digest down into significant amounts of sugar, while eating more protein and green veg,” says Dr Unwin. To put it into context – a slice of white bread is, on average, 16.6g carbs, a medium banana is 23g carbs and two teaspoons of jam are around 22g carbs. Dr Unwin believes while starchy carbs are complex, they still break down into substantial amounts of glucose. So, the idea is that on a low-carb diet you should replace these with more fibrous vegetables (such as broccoli, kale, sprouts and green beans), meat, fish, eggs and nuts. Is a low-carb diet right for me? If you have Type 2 diabetes (T2D), there’s evidence cutting the carbs could help, or even reverse, your condition. Research conducted by Dr Unwin of 154 patients with T2D or impaired glucose tolerance showed that following low-carb diets resulted in lower blood pressure, lower cholesterol, an increase in weight loss, as well as less reliance on medication. Elsewhere, the British Dietitians Association (BDA) say cutting carbs “can be effective in managing weight, improving glycaemic control and cardiovascular risk in people with Type 2 diabetes in the short term,” but impress there’s not been enough research done to determine the long term effects of the diet on their blood glucose, and the effects it can have on their heart health by swapping carbs for more fat and protein. It’s also important to mention that this does not apply to people with Type 1 diabetes, as well as children, teenagers and pregnant women with T2D. Likewise, those with gestational diabetes should seek help and advice from their midwife or doctor to ensure dietary changes help support both themselves and their babies. “Many of us, would benefit from cutting back on sugar which is just ‘empty’ calories,” says Dr Unwin, “With the epidemic of obesity, prediabetes, T2D and high blood pressure, cutting starchy carbs, possibly replacing with more green veg makes sense for a lot of people… but not all.” Low-carb might not be for everyone While there is emerging research highlighting the positive impact of low-carb diets on T2D, that doesn’t mean it’s suitable for everyone. The NHS says starchy carbohydrates should make up a third of the food you eat, recommending basing your meals around higher fibre wholegrain varieties of pasta, rice and bread. The NHS highlights that if we cut the carbs, we risk missing out on the important energy and nutrients they provide – including fibre, calcium, iron and B vitamins. “Some people may experience symptoms such as constipation, headaches, nausea and fatigue,” if they stop eating carbs says dietitian Tai. The BDA say restricting a food group isn’t something recommended "for many reasons, including dietary imbalance, contributing to complex relationships with food and compliance.” “As low-carb diet is a type of restrictive diet,” agrees Tai, “it may encourage disordered eating and an unhealthy relationship with food.” Sources of carbohydrates Can a low-carb diet result in weight loss? While some research suggests low-carbohydrate diets can aid weight loss (especially for those with T2D), Tai says, “there is no consistent evidence that a low-carb diet is any more effective than other approaches in the long term.” The BDA add losing weight on the diet isn’t sustainable for some: “At the moment, there are no clear definitions on what ‘low carbohydrate’ diets are.” This can make it difficult to manage this diet over this long term. For some people, a drastic reduction in their carbohydrate intake does help them to lose weight, but the BDA warns: “Most of the initial weight loss seen is often associated with water/fluid losses.” Be balanced If you’re thinking about going low-carb, it’s important to talk to an expert to make sure it’s suitable for you and that you’re eating a healthy, balanced diet, and finding alternative sources of fibre, energy and vitamins that carbs provide. Even if you're not planning on cutting carbs, the BDA recommends being 'carbohydrate aware', stressing that “it is important to choose the correct portion to suit your needs, less active individuals require less carbohydrates.” They suggest limiting the amount of free sugars you eat, and swapping white pasta, bread and rice for wholegrain versions will provide your body with extra nutrients. “Low-carb diets shouldn’t be seen as a one-size-fits-all diet for everyone,” ends Tai. “Most individuals need a balanced diet that includes a variety of starchy and wholegrain carbohydrates, fruits and vegetables that supports their health and wellbeing. However, if someone has to limit carbs for medical purposes, they should seek tailored dietary advice from their dietitian.” This article was published in January 2022. If you are concerned about disordered eating there is help and support available