The low-carb/high-fat diet revolution: It sounds unlikely — but the latest way to lose weight and stay healthy is to switch between two very different approaches…
- Growing evidence supports idea of switching between low-carb/high-fat diets
- Both have benefits, including weight loss and improvement of diabetic markers
- The possibility of diet-switching is central theme of new book, The Hybrid Diet
Settling on a sensible diet has never been harder.
A civil war is raging in the world of nutrition, pitching proponents of fats into fierce academic conflicts with those who favour carbohydrates as the route to good health.
An opening shot (though he didn’t know it then) was fired in 2014 when a Merseyside GP put 19 patients who were overweight or had type 2 diabetes on a diet that flew in the face of conventional advice to go low fat with plenty of carbohydrates.
That was Dr David Unwin, who featured in the Mail’s recent series on type 2 diabetes. He advised his patients to reduce the amount of starchy carbs they ate, including bread, pasta, rice and root vegetables, but include some high-fat foods such as olive oil and butter.
Instead of an average of 300g carbohydrates a day, their intake dropped to between 20g and 50g (one croissant has about 25g).
What would you do? Growing evidence supports idea of switching between a keto, low-carb diet
But crucially, they didn’t have to cut calories. The lost carbs were replaced with foods rich in fat which reduced hunger. After eight months, the patients’ blood sugar levels came right down, and they’d lost on average 9kg.
Follow-up studies found that 40 per cent had reversed their type 2 diabetes and their levels of unhealthy blood fats (eg, LDL cholesterol) had dropped. And their energy levels improved.
This low-carb diet is similar to the increasingly popular ketogenic diet; keto recipe books are now bestsellers on amazon.co.uk. ‘Keto’ involves eating even fewer carbs, which helps you burn fat for fuel rather than glucose (good for weight loss) and also comes with reports of feeling more energetic.
Does this mean we should all start the low-carb or keto diet? It’s a controversial area. When it comes to the keto, some experts argue that eating so few carbs is harmful long term. Another concern is that this diet doesn’t provide enough fibre.
Meanwhile a U.S. study published earlier this year in The Lancet claimed that following such a diet could take four years off your life because of the increased amount of animal fats it involves.
However, keto diet supporters make a strong case, too, pointing to the repeated failure of trials of low-fat diets to show they cut the risk of heart disease.
Another potential benefit is the suggestion that keto may turn on the body’s repair and garbage collection system, called autophagy, which is found in every cell.
Divisive: A civil war is raging in the world of nutrition, pitching proponents of fats into fierce academic conflicts with those who favour carbohydrates as the route to good health
Cells generate a lot of waste — dead and damaged proteins. Without a regular clean-up they gradually become less efficient.
Meanwhile, a year-long study of 349 obese diabetic patients on a low-carb diet found 60 per cent ended up with healthy blood sugar levels and they lost an average of 12 per cent of their body weight. So, if you’re struggling to lose weight or are pre-diabetic, which warring camp should you join?
Well, what if you could follow a diet that had the benefits of cutting carbs but allowed you to eat some of the carb-rich foods (bread, potatoes) these dieters often miss?
There is growing evidence to support the idea of switching between a keto, low-carb approach — eating a few grams of carbohydrates a day plus a good amount of fats — and another form of low-carb approach (without the high dose of fats) which keeps your blood sugar down but allows you a much greater range of the carbohydrate foods you may be craving.
Both diets come with health benefits, including weight loss and an improvement of diabetic markers, but switching between them may boost these results — and make them more sustainable.
The idea of switching between more and less intense dietary regimens is being explored by Professor Valter Longo, a biologist and gerontologist at the University of California. He developed what he calls the fasting mimicking diet, designed to provide the benefits of calorie restriction, which include weight loss and a drop in the blood markers linked with type 2 diabetes or heart disease.
His regimen, tested in the lab and with clinical trials, starts with a strict calorie restriction for five days, where participants limit themselves to a low-carb, high-fat diet of fewer than 1,000 calories from vegan sources a day.
Both diets come with benefits, including weight loss and an improvement of diabetic markers, but switching between them may boost these results — and make them more sustainable
After five days, participants switch back to a regular vegan diet, with more carbs and less fat, for three weeks. They revert to the fasting mimicking diet for five more days — and the cycle continues. Professor Longo claims one benefit, not yet fully tested, is being able to regrow malfunctioning cells, such as those in auto-immune diseases, so they are healthy again.
During the fasting period these cells shrink and some die. When patients switch back, the extra food allows them to regrow without the auto-immune defect.
Switching between diets means you don’t ban either fat or carbs — a perverse idea as our bodies have developed highly sophisticated systems to switch between them.
‘We can use fat and carbs for fuel as well as protein, because evolution favours adaptability,’ explains Richard Feinman, a professor of cell biology at the State University of New York.
Glucose (from carbs) is a major fuel for the muscles and the brain. What’s more, the body is designed to switch to running on body fat when glucose is in short supply.
In fact, your brain can’t run on fat itself, so our bodies can turn the newly-released fat into packets of energy called ketones. And the reason you don’t need to do calorie restriction to lose weight on the keto diet is that the carb deficit makes the fat release automatic.
The possibility of diet-switching is the central theme of my new book, The Hybrid Diet. Years ago, I became interested in why the recommended low-fat diet failed to halt the rise in obesity and diabetes.
As a medical journalist for 40 years, I came across research by the University of Oxford into the ketones produced by the low-carb ketogenic diet. This knowledge forms the basis of the ‘hybrid diet’, which combines the ketogenic diet and a low-carb diet, called low glyaecemic load (GL), a more sophisticated version of low GI.
On the GL diet you can have 150 or more grams of carbs but it still keeps blood sugar level healthy.
This is because not all carbs are created equal. Those rated low GL slowly release sugar into the blood, keeping it stable so you can safely eat more.
For example half a small serving of cornflakes has a high GL rating — the same as two bowls of porridge.
Other low GL foods include tuna and bean salad and oatcakes — they provide more carbs but don’t push up blood sugar (which is linked with type 2 and also makes it harder to lose weight without cutting calories as the body responds to constant high sugar by hanging on to its fat stores).
Switching to the ketogenic diet means cutting carb intake right down and significantly increasing fat intake — ie, meat and dairy, with avocados, nuts, seeds, coconut and olive oil.
The release of fat from fat stores is even greater when switching to keto because the body reacts to the drastic drop in carbs as it would to a famine.
Crucially, to make ketones, carb intake must drop significantly — below 30g. We vary in how quickly we can make the switch to ketone production, although usually the first time will take a week or more.It does get easier, however.
Professor Feinmann has found using the keto diet together with the low-GL option for weight loss useful. It’s possible that the hybrid diet could allow the two tribes — the proponents of fat and carbs — to call a truce.
Note: Always check with your doctor before starting any new diet plan, especially if you take prescribed medication.
The Hybrid Diet: Your Body Thrives On Two Fuels by Patrick Holford and Jerome Burne (Piatkus, £16.99).
WHAT IS OBESITY? AND WHAT ARE ITS HEALTH RISKS?
Obesity is defined as an adult having a BMI of 30 or over.
A healthy person’s BMI – calculated by dividing weight in kg by height in metres, and the answer by the height again – is between 18.5 and 24.9.
Among children, obesity is defined as being in the 95th percentile.
Percentiles compare youngsters to others their same age.
For example, if a three-month-old is in the 40th percentile for weight, that means that 40 per cent of three-month-olds weigh the same or less than that baby.
Around 58 per cent of women and 68 per cent of men in the UK are overweight or obese.
The condition costs the NHS around £6.1billion, out of its approximate £124.7 billion budget, every year.
This is due to obesity increasing a person’s risk of a number of life-threatening conditions.
Such conditions include type 2 diabetes, which can cause kidney disease, blindness and even limb amputations.
Research suggests that at least one in six hospital beds in the UK are taken up by a diabetes patient.
Obesity also raises the risk of heart disease, which kills 315,000 people every year in the UK – making it the number one cause of death.
Carrying dangerous amounts of weight has also been linked to 12 different cancers.
This includes breast, which affects one in eight women at some point in their lives.
Among children, research suggests that 70 per cent of obese youngsters have high blood pressure or raised cholesterol, which puts them at risk of heart disease.
Obese children are also significantly more likely to become obese adults.
And if children are overweight, their obesity in adulthood is often more severe.
As many as one in five children start school in the UK being overweight or obese, which rises to one in three by the time they turn 10.
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