Low-carb diets are back in a big way, but that doesn’t mean bread has to come off the menu. New research has found low-carb eating brings real health benefits — and drawbacks.
Are carbs your friend or foe? Low-carbohydrate diets are nothing new. From Atkins to Paleo and the trendy Ketogenic diet, carbs have been demonised so much they seem to have become the Darth Vader of our daily diets. But do they deserve their bad reputation? And are low-carb diets key to maintaining a healthy weight? We look at the science.
Fuel for your body
Carbohydrates are the petrol that fuels the body’s engine. In fact, they are the main energy source for your body, muscles and brain.
Carbohydrates come from the sugars and starches in food. When you eat a slice of bread, for example, the digestive process breaks it down into glucose and then releases insulin to help transport the glucose to your cells to be used for energy. The Glycaemic Index (GI) measures and rates this effect that carbohydrates have on your blood glucose and insulin.
If you don’t eat enough carbohydrates to maintain this steady glucose supply, your body is forced to start using protein or fat for energy. This is a back-up system that’s designed to see your body through a surprise famine, so it’s a considerably less efficient process.
Not all carbs are equal
Carbs are found in a range of foods, from carrots and legumes through to cakes and lollipops.
“What’s important is to choose healthier carbs found in whole grains, legumes [such as chickpeas], rice, fruit, starchy vegetables [like potato and corn], and in the lactose in foods like yoghurt and milk,” says dietitian and spokesperson for Nutrition Australia, Aloysa Hourigan.
Healthier carbs tend to have a low GI and are more slowly digested, absorbed and metabolised. Foods with a higher GI are digested quickly and tend to be higher in kilojoules and saturated fat (think mashed potato and croissants). They’re also low in fibre so they’re less filling, which can leave you hungry in a few hours and more likely to reach for a snack.
“The latest nutritional science has demonstrated that foods high in carbohydrates, in particular those foods with more refined and high-GI carbohydrates, cause a rapid elevation in blood glucose,” says Pennie Taylor, Senior Research Dietitian for the CSIRO and co-author of the new CSIRO Low Carbs Diet Plan. “Over time, if not controlled, this can lead to type 2 diabetes, heart disease and other adverse health outcomes.”
Carbohydrates and weight loss
Some people find that cutting carbs helps them lose weight faster. “To lose weight on a low-carb diet, you don’t need to stop eating all carbohydrates, but you do need to make sure that the carbs you eat are good quality — for example, vegetables and unrefined grains,” says Taylor.
The CSIRO Low Carb Diet Plan is the latest low-carb approach to weight. Unlike many ‘fad’ diets over the years, it’s backed by science. Plus, there’s more good news for carb-lovers — bread doesn’t have to come off the menu.
The eating plan recommends reducing your carb intake to just 50g for the first six weeks. (This is less than one-third the daily carbs that the average Australian eats.) Carbs can then be increased to 70g daily, if desired.
“We also recommend spreading carbs across the day — for example, eating 15g at each meal as opposed to 45g in one sitting,” Taylor says.
To reduce hunger, Taylor recommends you include protein and healthy fats in the form of olive oil, seeds, nuts and avocado. These fats help you feel full, and the smooth and creamy texture can increase the palatability of foods.
How many carbs do I actually need?
Aim for four to six serves every day. One serve is:
1 slice wholegrain bread
1 small wholemeal roll
1/2 cup porridge
1/4 cup muesli
2/3 cup flaky wholegrain cereal
1/2 cup cooked brown rice or barley
Confused about carbs? We answer your most frequently asked questions.
Q. Which bread is best?
"Many wholemeal and light rye breads contain very fine flours and have an elevated Glycaemic Index rating,” says Alan Barclay from the Dietitians Association Australia. A better option is a dense, wholegrain loaf with visible seeds and grains.
Q. Are potatoes fattening?
Quite the opposite! The humble spud is naturally low in fat. One medium potato has zero grams of fat and just 425kJ (102cal), with the added bonus of fibre, potassium and vitamin C. The real key to a healthy potato is how you prepare it. Turn that same spud into deep-fried potato chips and this swells to 16.8g fat and 1143kJ (273cal)! Lashings of butter and sour cream also add kilojoules.
Q. Should I cut out starchy carbs?
"It’s a myth that starchy vegies like corn, pumpkin and carrots should be avoided if you want to eat a healthy diet and maintain your weight,” says Barclay. “Humans have eaten starchy vegetables like tubers and roots for a very long time with good reason, because these vegetables are healthy, highly nutritious and reduce hunger.”
Q. Should I limit carbs at night?
Yes, reducing carbohydrate foods with dinner can be a simple way of reducing your overall daily kilojoule intake.
But if an unbalanced meal leaves you feeling hungry and sends you in search of sweets an hour or so later, then it’s not a good choice or the outcome you want.
“There’s nothing inherently fattening about carbohydrates, no matter when you choose to eat them,” says Advanced Accredited Practising Dietitian, Dr Tim Crowe.
“It’s actually eating too many kilojoules that will load on the extra kilograms.”
Low-carb diets decoded
Don’t know your Paleolithic from your Ketogenic? You are not alone! Here’s the lowdown on low-carb diets — and what they actually do.
Reaching its peak popularity in 2013, the Paleo is a high-protein, low-carbohydrate diet that eliminates grains, legumes and dairy foods from your meals.
The Paleo diet’s main positive is the focus it puts on whole foods and the reduction it brings about in processed foods, sugar, salt and alcohol.
Low in fibre: “This may cause constipation, and in the long term the lack of fibre may also increase the risk of bowel cancer,” says Dr Alan Barclay, dietitian and spokesperson for the Dietitians Association of Australia (DAA).
Excessive meat intake: “Too much protein can stimulate insulin,” says Barclay. “If people eat a great deal of red meat, then this could also predispose them to bowel cancer.”
This ultra-low-carb diet aims to get your body to use ketones, from stored fat, as its preferred fuel source, instead of carbs. Ketones are produced by the liver from fat when the body is starved of carbohydrates. The Keto diet cuts your carbs to 50 grams per day, the absolute minimum required for our brain, nervous system, red blood cells and kidney function.
This extreme diet may alleviate symptoms in conditions like epilepsy and multiple sclerosis, but some are adopting it to achieve major weight loss.
High in saturated fat: It can boost unhealthy LDL cholesterol, bumping up your risk of heart disease.
Hard to sustain: “Most people can’t stay on a ketogenic diet for more than a few months because it’s too rigid and restrictive,” says Barclay.
A low-carb diet aims to cut carbs to between 50 to 70g per day, which is about one-third of what the average Australian usually eats.
Most of us could benefit from cutting back on refined, processed carbs such as white bread, cakes, pastries and biscuits. Some people find they lose weight more easily when they reduce their overall intake of carbohydrates.
Lack of energy: Feeling tired is a common gripe among those on a low-carb diet, and it can lead to eating more between meals and skipping exercise.
Digestive issues: “Reducing the intake of grains, which are a good source of fibre, can cause many people to become constipated, and some may also develop unpleasant-smelling flatulence,” says Aloysa Hourigan from Nutrition Australia.
Drop in mood: There’s a connection between carbs and mood. People who are on a low-carb diet experience more depression, tension, anxiety and feelings of hostility, research by Flinders University and the University of South Australia shows.
Low carb, high fat
Also known as ‘LCHF’, this diet encourages the intake of high-fat foods like cream, butter and bacon, as well as protein-rich foods such as eggs, meat, chicken and fish. Grains, bread, pasta and starchy vegetables such as potato are restricted under this diet — and even fruit.
Research in mice has suggested that this diet may help to reduce those human brain proteins that contribute to Alzheimer’s disease.
Weight gain: After just eight weeks on an LCHF diet, mice gained 15 per cent of their body weight and their fat mass rose from 2 per cent to almost 4 per cent, according to recent research from Melbourne University.
Lead author of the study, Associate Professor Sof Andrikopoulos, recommends the Mediterranean diet instead, because it’s “low in refined carbs and contains whole grains, legumes, plant foods, and healthy fats from fish and extra-virgin olive oil.”
Slow carbs trump low carbs
There’s no need to ditch all carbs to lose weight and be healthy — just choose better carbs. Whole grains, legumes and vegetables are slowly digested — which makes them a big win for your health. Here’s why you’ll love slow carbs:
High in fibre: “Foods that take longer to chew and digest help to keep you full for longer,” says spokesperson Alan Barclay from the Dietitians Association of Australia.
Long-lasting energy: The slow release of energy also prevents rapid spikes and slumps in blood sugar levels, giving you sustained energy.
Stable blood glucose levels: Blood glucose is more slowly released from your gut and is more slowly trickled into your bloodstream, causing a lesser rise in insulin levels.