What Carbohydrates Really Are
Like proteins and fats, carbohydrates are macronutrients – in other words, substances that stoke your metabolism and keep you alert and active. As an analogy, think of carbs as your body’s primary source of crude oil. Through digestion, carbs are transformed into glucose – similar to high-octane petrol.
“Carbohydrates are the only nutrients that exist solely to fuel the body,” says Dr Donald Layman, professor emeritus of nutrition at the University of Illinois. Without glucose, your blood oxygen levels suffer, your energy levels tank and your risk of a brain fart rises.
You should consume 45-65 per cent of your daily kilojoules from carbs, according to the most recent recommendations. So if you’re a moderately active guy eating 11,000 kilojoules a day, that means 4950-7150 kilojoules of that total should come from carbs. And since carbohydrates – whether from sugar, starch or fibre – contain 17 kilojoules per gram, you should shoot for 295-425g a day. This amount, says Layman, will help your brain, blood and nervous system function at their best.
If you keep your intake under 80g of carbs a day, as some diets suggest, your body will begin breaking down its fat stores to produce ketones, a poor man’s “glucose”, which can lead to that low-carb “cloudy” feeling. Excess dietary carbs become excess body fat. So losing weight and helping your heart is as simple as cutting back on the white bread, right? Read on.
Why You Should Strive for Complexity
The quality of your carbs is as important as the quantity, says Dr Frank Sacks, professor of cardiovascular disease prevention at Harvard School of Public Health. Complex carbs, found in starchy vegetables and whole grains, are linked to healthier weight and a lower risk of type 2 diabetes and heart disease.
Complex carbohydrates are difficult for the body to break down – and that’s a good thing. These carbs are digested slowly, and the absorption of sugars into your bloodstream is also slower as a result. The increases in your blood sugar and insulin levels are moderate enough that they don’t reach levels associated with body-fat storage.
Plus, they make your good gut bacteria happy. “The gut microbiota prefer complex carbs over any other food source,” says gastroenterologist Dr Gail Cresci. After these microbes feast on the carbs, they send beneficial compounds into your bloodstream. These compounds, called short-chain fatty acids, may help lower inflammation and strengthen your immune system, says Cresci.
Most foods that contain complex carbs are also high in fibre (another form of carbohydrate), which regulates blood sugar and helps you feel full. In a 2015 study published in the Annals of Internal Medicine, people who were asked to eat 30g of fibre a day on top of their normal diet lost about as much weight as subjects who maintained a strict diet.
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How the Wrong Kinds of Carbs Can Hurt You
Refined carbs, such as those in white bread, biscuits and chips, have the opposite effect that complex, unrefined carbs do. After you eat, say, a doughnut, your blood sugar rises; in response, your insulin levels skyrocket. Plus, your gut bacteria spit out inflammatory compounds, says Cresci. So that little treat, if it becomes habit, can set you up for metabolic malfunction, elevated triglycerides, obesity and the chronic diseases that accompany them.
Cutting out those doughnuts may help you erase the one encircling your waistline. And yes, if you eliminate almost all carbs from your diet you’ll drop even more weight – but not for the reason you might think.
On a low-carb diet, your body churns through its stores of muscle glycogen. And for every bit of muscle glycogen you burn, your body releases twice as much water, Cresci says. So initially you’ll lose weight, but it will be more from water than from body fat.
To effectively reverse the weight gain associated with the intake of simple carbs, you have to shop smart.
Beware of products that market themselves as low-fat. When food manufacturers remove fat from ice-cream, yoghurt or salad dressings, they often replace the lost flavour with processed sugar (yes, sugar is a carb), which is more easily converted into body fat than unprocessed carbs.
And don’t let the “gluten free” trend hook you in: many gluten-free products contain more sugar and kilojoules than their conventional counterparts. In fact, a 2014 review published in the Journal of Medicinal Food concluded that people who followed a gluten-free diet had a greater risk of obesity later in life than those who didn’t. So unless you’re among the small minority of Australians who have coeliac disease or known sensitivity, there’s probably no health reason for you to cut out gluten-containing whole grains like wheat, barley and rye. And don’t forget: gluten is a form of protein, your muscles’ friend.
Anyone who cuts down on fruit to reduce their sugar intake is making a big mistake
How Carbs Fuel Your Fitness
Carbohydrates are stored as glycogen in your muscles and liver, and also serve as fuel for high-intensity and endurance exercise. If your routine is intense, you need 40-60 additional grams of carbs per hour of exercise to help your performance.
Another way to think about this is one extra gram of carbs per minute you work out. According to 2013 research in Sports Medicine, carbs boost performance during endurance and high-intensity workouts. Better performances burn more kilojoules.
And while carb loading before a race is a must, no evidence suggests that switching between high- and low-carb days (or “carb cycling”) helps performance. Some experts say it may even hurt your health. Shifting between low and high insulin levels can cause low-grade systemic inflammation, says Cresci.
After your workout, you need to consume just as much carbs as protein – ideally more. That’s because insulin may help with protein synthesis and muscle building, a 2015 study in the Journal of the International Society of Sports Nutrition suggests. Aim for a 1:1 or 2:1 carb-to-protein ratio after you hit the gym.
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