Why cutting out carbs needs a rethink

When it comes to long-term weight management, research shows cutting out carbs isn’t the answer. So why are low-carb diets still popular? And what should you do instead?

For decades, from the Atkins diet to “going keto”, carbohydrates have been cast as being “bad” as far as losing weight or keeping it off is concerned.

But recent research shows carbohydrates aren’t necessarily the enemy; and according to a 2022 review of more than 60 randomised controlled trials, long-term low-carb dieters lose just under a kilogram more weight than people on balanced-carb diets when the total amount of kilojoules are the same.

So why are low-carbohydrate diets still the go-to when it comes to weight loss?

Why low-carb diets are so popular

“Like every fad diet, low-carb diets make one thing – in this case, carbohydrates – the enemy, which means the message is nicely packaged and easy to understand,” dietitian Milly Smith says.

“The idea is if you just cut this one thing out, you’ll get the results you’re after, which seems simple but, unfortunately, it oversimplifies the role of carbohydrates and ignores how important they are for our bodies.

“For one thing, carbohydrates are our brain’s preferred source of energy, so when we cut them out, we can’t function at our best.”

Not all carbohydrates are created equal

While carbohydrates are found in breads, cereals and other grains, as well as in fruit, vegetables and milk, they’re also found in ultraprocessed fast foods, cakes, chips, biscuits and confectionery.

Milly believes this fact contributes to the “avoid carbohydrates at all costs” message.

“Some of those more discretionary foods, which we shouldn’t be eating too frequently, do fit into the ‘carbohydrate group’,” she says.

“And cutting back on those can certainly help with weight loss but, unfortunately, when we blanket carbohydrates all together, we don’t see the full picture.”

What the research on dietary carbs says

Research agrees – while healthy carbs are packed with dietary fibre, vitamins, minerals and phytonutrients, studies show low-carbohydrate diets can lead to nutritional deficiencies.

Research conducted by the University of Sydney’s Charles Perkins Centre shows processed foods are a key contributor to high obesity rates in the Western world.

The study suggests that as people consume more highly processed and refined foods – aka “junk foods” – they dilute their dietary protein and increase their risk of being overweight.

“It’s increasingly clear that our bodies eat to satisfy a protein target,” Professor David Raubenheimer, one of the study authors, says.

“But the problem is that the food in Western diets contains increasingly less protein, so you have to consume more of it to reach your protein target, which effectively elevates your daily energy intake.”

Prof Raubenheimer explains that humans, like many other species, have a stronger appetite for protein than for the main energy-providing nutrients of fats and carbohydrates.

“That means that if the protein in our diet is diluted with fats and carbohydrates, we will eat more energy to get the protein that our bodies crave,” he says.

Protein is key

Trying to lose weight? Aim for a higher-protein, moderate-carbohydrate diet.

That’s the message delivered in a report released by Australia’s scientific research agency, CSIRO.

The takeaway advice? Eating more protein, especially at breakfast, could be the key to achieving healthy weight loss, thanks to the way it controls hunger and enhances muscle metabolism.

The report recommends eating at least 25g of protein at main meals.

“It’s not difficult to include a source of protein in every meal – it may just take a bit of a mindset shift and some planning,” Milly says.

“Becoming familiar with protein rich foods, and knowing which naturally ‘fit’ your morning meal – for example, eggs and yoghurt – is a great place to start.”

And when it comes to carbohydrates, Milly recommends eating foods rich in the complex variety, some of which are also good sources of protein.

“Eating complex carbohydrates like legumes, wholegrains and nuts, as well as fruit and vegetables, provides dietary fibre as well as a wide variety of other nutrients we need for good health,” she says.

Written by Karen Fittall.