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Most low-carb diets are founded on junk science. Fibre-rich whole grains and root veg can play a crucial role in providing you with energy and micronutrients
Carbohydrates get a bad rap when it comes to weight loss. Conventional wisdom has us believe that to lose weight, we must limit – or eliminate – carbs in our diet. But it’s not that simple. In reality, carbs – sugars and starches found in grains, fruits and vegetables – provide crucial, fast-acting energy to feed your brain, muscles and metabolism. And when they’re not processed into pastry form, they also contain a lot of the minerals, vitamins and fibre needed to maintain good health. In fact, carbohydrates are generally your body’s main (and preferred) source of fuel.
The problem is, many eating plans from the past two decades cast carbohydrates as the enemy of weight loss. These diets demonise all carbs, from oats and lentils to fruit, and urge you to exorcise them from your life. It’s true that by limiting highly processed carbs you can make weight loss a whole lot easier. But shunning the good stuff can hinder your health and fitness goals. Read on to learn how to slice it.
Carbs, like proteins and fats, are macronutrients – energy sources that keep you alert, active and, well… alive. Think of carbs as your body’s primary source of crude oil. Through digestion, carbs are transformed into glucose, kind of like high-octane unleaded gas. ‘Carbohydrates are the only nutrients that exist solely to fuel the body,’ says Donald Layman, a nutrition consultant at the University of Illinois. Without glucose, your blood oxygen levels suffer, your energy levels tank and your brain gets foggy.
You should aim to get 45% to 65% of your daily calories from carbs. If you’re a moderately active man consuming 2,600 calories a day, that means 1,170 to 1,690 calories should come from carbs. And since carbs – whether from sugar, starch or fibre – contain four calories per gram, you should shoot for 295g to 425g a day. This will help your brain, blood and nervous system function at their best, says Dr Layman.
If you keep your intake under 80g a day, as some diet plans suggest, your body will begin to break down fat stores to produce ketones to use as fuel, which can lead to that low-carb cloudy feeling. Excess dietary carbs, like all calories, are stored as body fat. You want to strike a balance.
There’s more to it than grams and portion sizes, however, says Frank Sacks, a nutrition professor at the Harvard TH Chan School of Public Health. The type of carb matters, as well as how much you eat. Complex carbohydrates, found in starchy veg and whole grains, are linked to healthier weight and lower risks of both type 2 diabetes and heart disease.
‘Complex carbohydrates are difficult for the body to break down, and that’s a good thing,’ says Gail Cresci, a researcher in gastroenterology and nutrition at Cleveland Clinic. These carbs digest slowly, meaning the absorption of sugars into your bloodstream is slower, too. The increases in your blood sugar and insulin levels are moderate enough that they don’t reach levels associated with body-fat storage, Dr Cresci says. Plus, your gut likes them – in more ways than one. ‘The gut microbiota prefer complex carbs over any other food source,’ says Dr Cresci. After your gut bacteria feast on carbs, they send compounds called short-chain fatty acids into your bloodstream, which may help lower inflammation and strengthen your immune system.
Most foods that contain complex carbs are also high in fibre, which helps you feel full. In one study, people who were asked to eat 30g of fibre a day on top of their usual diet lost about as much weight as those who were following a strict (and probably far less enjoyable) meal plan.
Refined carbs – those in white bread, biscuits and crisps – have the opposite effect of the complex kind. After you eat, say, a jam doughnut, your blood sugar rises, your insulin levels jump up and your gut bacteria spit out inflammatory compounds, says Dr Cresci. The odd indulgence won’t do any damage, of course. But too much too often will set you up for potential metabolic malfunction.
It’s true that if you eliminate almost all carbs from your diet you’ll drop a lot of weight – but not for the reason you might think. On a low-carb diet, your body churns through its muscle glycogen stores. And for every bit of muscle glycogen you burn, your body releases twice as much water, Dr Cresci says. So those initial kilos you drop will be from water, not just body fat.
Eating more oats, quinoa, beans and sweet potatoes and fewer pastries sounds incredibly simple, but there are some traps to look out for. Beware of products that market themselves as low fat. When food producers remove fat from foods such as yoghurt or salad dressings, they often replace the lost flavour with processed sugar (a carb), which is more easily converted into body fat than unprocessed carbs, Dr Cresci says. You’re better off sticking with the real deal.
Don’t let the gluten-free trend hook you in, either: many free-from foods contain more sugar and calories than conventional counterparts. Unless you’re among the relatively small minority of people who have coeliac disease or a known sensitivity, there’s probably no need for you to swerve grains such as wheat, barley and rye.
And, finally, to settle the debate on fruit. While berries, bananas and the like contain simple carbs, they come with plenty of fibre, which slows their absorption. In fact, a recent BMJ study found that fibre from fruit may reduce your risk of heart disease. ‘Anyone who cuts down on fruit to reduce their sugar intake is making a mistake,’ says Dr Sacks.
Carbs are stored as glycogen in your muscles and liver, serving as fuel for high-intensity and endurance exercise. If your fitness regimen is intense – say, you’re training for a marathon – you need an extra 40g to 60g of carbs per hour of training to perform at your peak, says Stuart Galloway, who studies exercise metabolism at the University of Stirling, Scotland. Another way to think about this is one additional gram of carbs per minute you work out.
As for ‘carb cycling’, there’s no robust evidence to suggest that switching between high- and low-carb days helps performance. Some experts say it may even harm your health by contributing to low-grade inflammation, says Dr Cresci.
After your workout, you need to restock those carbs as well as taking in protein. Raising levels of insulin can help with protein synthesis and muscle building, a study in the Journal Of The International Society Of Sports Nutrition suggests. Aim for a 1:1 or 2:1 carb-to-protein ratio post-gym. Some good choices are chocolate milk (really), sliced apple with almond butter, or pitta and hummus.
The bottom line? Eat a consistent amount of complex carbs every day (unless you’re running a marathon or doing something similarly hardcore) from a variety of whole-food sources. For an appetising prescription, try our recipes over the page.