If you see carbs as the enemy, it’s time to read up on the facts. Not only do they fuel our bodies, but certain types may help us lose weight…
We all know that cakes, biscuits and white bread are high in carbs. So, too, are chips, crisps and pastries. If you find these foods are derailing your good health intentions, it seems logical to think drastically cutting back on carbs might be the sensible solution. Going low carb has gone from being a diet fad to a mainstream lifestyle choice, taking over from eating low fat or counting calories as the fashionable way to lose weight. Diets such as Atkins first popularised this, but today it’s social media that stokes the low-carb fire. ‘Health’ bloggers rave about clean eating and ditching wheat and sugar, hailing low-or-no-carb eating as the key to burning fat and shedding lbs fast. At the time of writing, #lowcarb has been used over five million times on Instagram alone. So are they right – should we see carbohydrates as the devil in our diet? It’s time to get back to the nutrition basics.
What are carbohydrates?
They’re one of the three main or ‘macro’ (ie, needed in large amounts) nutrients in our diet, the others being protein and fat. ‘Hardly any foods contain just one macronutrient, and most contain a combination of carbohydrates, fats and proteins in varying amounts. Your body needs all three to function properly,’ explains HFG dietitian Jennifer Low. ‘There are three main types of carbohydrate: sugars, starches and fibre,’ Jennifer continues. ‘Sugars and starches are broken down by the body into glucose before being absorbed into the bloodstream. From there, glucose enters the body’s cells with the help of insulin, which is released from the pancreas.’ Glucose helps make energy to fuel the body. Unused glucose can be converted to glycogen, which is found in the liver and muscles, or it can be converted to fat for long-term storage. ‘As for fibre, this is the part of food that is not broken down. It helps you to feel full and this can help you maintain a healthy weight,’ says Jennifer.
Why do we need carbs?
Put simply, to get through the day! Carbohydrates are our body’s basic fuel – like petrol in a car. They should account for around 50% of our daily energy intake (about 250g a day). ‘Glucose from carbs is the main source of fuel for our brain and muscles,’ says Helen Bond, spokesperson for the British Dietetic Association (BDA). If you’ve ever been really hungry and felt “hangry” (hungry + angry) or experienced brain fog, low mood and fatigue on a low-carb diet, it’s because your glucose supply is low. Your brain needs carbs. ‘Carbs are particularly important for people who are physically active,’ adds Jennifer. ‘A diet too low in carbs can lead to a lack of energy during exercise, early fatigue and delayed recovery. Likewise, you need to replenish depleted energy stores after exercise with a carb-rich snack or meal, such as a banana smoothie.’ Carbohydrates provide other important nutrients, too. Vegetables, pulses, wholegrains and potatoes (skin on) all provide fibre to help promote bowel health, reduce the risk of constipation, lower cholesterol and help us feel full. They also provide us with vitamins and minerals, including calcium, iron and B vitamins.
Don’t they make you put on weight?
‘There’s a body of research that suggests low-carb diets are more efficient than other weight-loss plans, such as low-fat,’ says Jennifer. ‘But it’s the type and quantity of carbohydrates in our diet that’s key. They’re not all the same – the term covers a broad range of foods, including fruits, vegetables, grains and dairy products. And, contrary to what some social media influencers might claim, the right kinds of carbohydrates can help you lose weight, keep it off and ensure you get longer-lasting satisfaction from your meals,’ she says.
The weight-loss connection
‘Restricting calories results in weight loss, regardless of whether you cut out carbs, fat or protein,’ says Jennifer. In fact, according to some studies, when diets low in carbs were compared with diets that weren’t, the amount of weight lost was the same. One meta-analysis, published in the British Journal of Nutrition, found that participants on low-carb diets experienced greater reductions in body weight and fats in the blood called triglycerides than those on low-fat diets, but greater increases in both HDL (good) cholesterol and LDL (bad) cholesterol. The authors concluded that the beneficial changes of low-carb diets must be weighed against the possible detrimental effects of increased LDL cholesterol. Cakes, biscuits and confectionery are high in carbs in the form of sugars, but they’re also high in fat and, importantly, calories.
‘When people lose weight after cutting these foods from their diet, they often wrongly attribute the weight loss to being on a low-carb diet,’ Helen points out. But there are other high-carb foods that don’t carry this extra fat and sugar, such as lentils, grains and starchy veg. ‘These foods are loaded with fibre and a raft of vitamins and minerals,’ she says. Bread gets a bad rap, too, but white, fluffy bread is different from dense, wholegrain loaves with seeds and grains. Similarly, puffed rice breakfast cereal coated in sugar is high in carbs and rapidly digested, but so is a bowl of nutritious, slowly-digested muesli. ‘There’s good evidence to show people who eat lots of wholegrains weigh less than those who eat very few,’ says Helen. ‘More proof that losing weight is not about cutting out all carbs – it’s the type of carbohydrate you reduce that does the trick.’
So do low-carb diets work?
In the short term, yes – but so does any other plan where calories are restricted. ‘The success of any diet relies on how easily you can stick to it and how healthy it is,’ says Helen. ‘And low-carb diets – usually defined as below 130g carbs a day or below 30g if very-low-carb – don’t rate well on these.’ Following a very low-carb diet can mean missing out on vital nutrients, as well as increasing other health risks. ‘Bear in mind that cutting out carbs and replacing those calories with fats and higher-fat sources of protein can increase your saturated fat intake, which may in turn increase heart disease risk,’ warns Jennifer. There’s also the matter of bad breath… ‘The body will always try to keep a minimum amount of glucose circulating at all times,’ says Helen. ‘When it isn’t getting enough energy from carbs and your glucose stores are exhausted, it turns to burning primarily fat for fuel. During this process, ketones are produced (ketosis), which smell like acetone.’ So that explains the unpleasant mouth taste and breath often experienced while on a low-carb diet – as anyone who’s followed Atkins will recall. Low-carb diets that are high in protein can also be a potential problem if you have an underlying kidney problem – something you may be unaware of.
Slow carbs aka low GI
Just as you want to put the best quality fuel into your car for peak performance, you want to fuel your body with high-quality, long-lasting carbohydrates. These include wholegrains such as barley and quinoa, high-fibre cereals, beans and legumes, and fruit and starchy vegetables such as sweet potatoes.
We could call these types of carbs ‘good’ or ‘slow’ carbs. ‘Our body digests these foods slowly so they provide long-lasting energy,’ says Jennifer. ‘You might also hear them referred to as low-GI foods.’ The Glycaemic Index (GI) measures the rate at which carbohydrates are digested. High-GI foods – think white bread, white rice, biscuits and cakes – are digested quickly, giving a rapid surge in energy that drops soon after. This not uncommon sugar crash leaves us feeling hungry, even if only a short amount of time has passed since we last ate. ‘Choosing low-GI carbohydrates will keep you feeling fuller for longer, which can help with weight control,’ advises Jennifer. ‘Low-GI carbohydrates also help to manage blood glucose and insulin levels, which, in the long term, helps to reduce your risk of developing type 2 diabetes and heart disease. So they’re the all-round wise choice for good health and weight maintenance,’ she says.
More on the big three
Dietitian Jennifer Low talks you through the types of carbohydrates:
Fibre is only found in foods that come from plants. Fibre helps keep our bowels healthy, and some types may even help lower bad cholesterol. Research also links high-fibre diets with lower risks of cardiovascular disease, type 2 diabetes and bowel cancer. Foods that give us fibre include wholegrain bread, wholewheat pasta, pulses such as beans and lentils, root vegetables, nuts, seeds, oats and fruit.
Starch is made up of many intrinsic sugar units bonded together. It’s found in plant-derived foods such as bread, rice, potatoes, pasta and couscous. These provide a slow, steady release of energy throughout the day, and should be part of every meal (see Which carbs and how much?, overleaf).
Sugar is found naturally in fruit, milk (as lactose) and some veg, but these ‘intrinsic’ sugars don’t count towards our daily sugar maximum of 30g. Other forms of sugar are added to food. Plus honey, syrup and nectars (such as maple or agave), although natural, fall into the added sugars bracket, just like table sugar and treacle. These count towards the daily max. Read the truth about sugar in food here.
Good to Know
‘Wholemeal bread has a high GI because of the fine milling of the bread flour to achieve a smooth texture,’ says the BDA’s Helen Bond. ‘But it’s still a better choice than white bread for fibre. Also, when eaten as part of a meal containing protein and fat, such as wholemeal bread with poached eggs, the overall absorption of the carbs is slowed down, which lessens the impact of their initial high-GI value.’