Tue, Dec-15-20, 13:02
Should you give up carbs? Here’s why starchy foods aren’t the enemy
In the US, campaigners are calling on the government to reduce the recommended carbohydrate intake — but plenty of experts aren’t convinced
Are carbohydrates the dieter’s worst enemy — delicious, but a surefire way to gain weight? Or are they the opposite: high in nutrients and fibre, and part of any balanced regimen?
On the other side of the Atlantic, this debate is being played out in high-profile style. The US Department of Agriculture and the Department of Health and Human Services are reviewing nutritional guidelines. Updated every five years, they advise on everything from carbohydrate intake to safe alcohol levels.
Some campaigners, who blame calories from carbs for causing epidemics of obesity and type 2 diabetes, want the government to slash its recommended daily intakes. Where America leads, Britain usually follows.
In the US and Britain it is recommended that people get half their calories from eating carbohydrates
The US recommends that people get half their calories from eating carbohydrates. So does Britain. However, in heated public hearings over the past 18 months, American low-carb advocates have pushed for guidelines to advise halving their recommended daily carbohydrate intake for millions of overweight people, to 25 per cent or less (about the same as the Atkins diet). In Britain, an official panel of leading dietary experts has put new draft guidelines on low-carb diets out for consultation, with the results due next year. Which way will we go in the war on carbs?
The case for cutting carbs
Low-carb regimen backers claim that carbohydrates not only can cause weight gain, but also pose a particular diabetes risk because eating them can cause glucose levels in the blood to spike, with the body responding by rushing to produce insulin to regulate the blood sugar. Supporters argue that when these sharp insulin rises happen too often, the body becomes physically resistant to insulin and this can lead to type 2 diabetes.
They claim that by radically cutting carbs from their food, dieters can achieve such a significant and lasting change in their metabolisms and weight that their bodies’ insulin-regulation systems revive and the diabetes is reversed.
A report by investigators at the American Diabetes Association last year said they had found sufficient evidence to suggest that very low (less than 26 per cent) carbohydrate diets can be helpful in lowering diabetics’ blood-sugar levels and also their use of medication.
Removing carbs seems to be a simple way to remove calories from your diet, which is why it may help you to lose weight
Short-term gain, long-term pain?
A US federal advisory committee that has explored the low-carb claims has indicated this year that there is no conclusive evidence to support a radical reduction in national carb consumption. Furthermore, in March the UK’s Scientific Advisory Committee on Nutrition (SACN) produced its own draft conclusions, finding that low-carb diets show no long-term health advantages over higher-carb regimens.
The report, which was commissioned by Public Health England, examined the best clinical-trial evidence on differing diets’ benefits for people with type 2 diabetes. For weight-loss it concluded that, after a year, there was no meaningful difference between low-carb diets and normal-carb diets.
The independent committee also found that, for lowering blood-glucose levels, low-carb diets might have better short-term results — but that there was no evidence to show they were any better than normal-carb diets over the period of a year or more.
Present UK dietary advice is the same for diabetics and non-diabetics: about 50 per cent of dietary energy should be from starchy carbs (such as potatoes, bread and rice), preferably high-fibre or wholegrain.
Consultation on the SACN draft report ended in April and a spokesman for Public Health England says the final report is due to be published “next year – but there are no specific timings”.
The calorie equation
Roy Taylor, professor of medicine and metabolism at the University of Newcastle, was the world’s first researcher to demonstrate that diabetes is reversible through weight loss, in 2011.
He did this by showing that type 2 diabetes is not caused by excessive glucose spikes caused by carbohydrates, but by overweight people’s bodies storing excess fat in the liver and pancreas. This overload causes insulin production to shut down. If that fat is lost by dieting, insulin production recommences.
To reduce patients’ weight, Taylor worked with Glasgow University to create a crash-course liquid diet. After crash-dieting, patients need to maintain their healthy weight. But that doesn’t necessitate any particular level of carb intake, he says.
“It is not the composition of your diet that matters, it’s the total amount of calories,” he says. “Moderation is the key, however you do it — be it intermittent fasting, moderately low carbs, or low fat.”
Certainly he says there should be no biscuits, crisps or similar snacks. That’s all about cutting calories not carbs, though. If you eat healthy carbohydrates instead, in the form of fruit or veg, that’s fine, Taylor adds.
A Mediterranean diet is typically about 40 per cent carbs
Quality of carb counts . . .
Helen Bond, a registered dietitian and spokeswoman for the British Dietetic Association, says that removing carbs seems to be a simple way to remove calories from your diet and may help you to slim.
“But not all carbs are created equally,” she says. “It’s important only to reduce free sugars, as found in soft drinks and sweet snacks, for the sake of our waistlines.”
NHS guidelines say we should consume no more than 30g of free sugars a day (seven sugar cubes). That’s easily exceeded: a 12oz can of Coca-Cola contains 39g of sugar.
Healthy diets can happily contain significant levels of carbs, Bond adds. “When you look at a regime such as the Mediterranean diet, it’s about 40 per cent carbs. These are what our body and major organs, including our brain, use as a main fuel.
“People forget that fibre is carbohydrate. The fibre in starchy carbs is especially good at helping to keep our digestive system healthy. Gut health, in the form of your microbiome, is important for general health. Fibre acts as a fertiliser for friendly microbes.”
Some forms of fibre (such as oat beta glucan) can also help to reduce cholesterol levels, Bond says. And fibre from wholegrains is linked to a reduced risk of developing type 2 diabetes, as well as heart disease.
. . . so does portion size
The key, Bond stresses, is not to overload on carbs, but to stick with healthy serving sizes: a tennis ball-sized serving (about 150g) of cooked pasta, rice, noodles, couscous or other grains; one handful or five level tablespoons (30g) of wholegrain breakfast cereal; one potato the size of a computer mouse (180g); and one to two slices of wholegrain bread.
Such sentiments are echoed by Natasha Marsland, the senior clinical adviser at Diabetes UK. “While a low-carbohydrate diet can help some people with type 2 diabetes, it’s not the only option,” she says. “The Diabetes UK-funded DiRECT trial [being led by Professor Taylor] has shown that a low-calorie diet, alongside support from a healthcare professional, can help put people with type 2 diabetes into remission following weight loss.”
The key, it seems, lies not in condemning food groups, but in sensible, healthy eating. As Taylor puts it: “People who shout about low carbs or low fat just distract from the real cause of the problems — the fact that we are being fed calorie-packed processed food that is not good for us.”