Gary Taubes: 'Obesity isn’t a calorie problem, it’s a hormone problem'
Over the past two decades, the UK’s rates of obesity and type 2 diabetes have spiralled, something that has invariably been blamed on our intake of saturated fat. Conventional nutrition science argues this leads to elevated cholesterol levels and a greater risk of heart disease, but journalist Gary Taubes believes we need to rethink this idea. Over the past 20 years, Taubes has suggested that fat has been unfairly demonised, and instead our excessive carbohydrate and sugar consumption is to blame for many of these societal health problems, a concept that has begun to interest increasing numbers of scientists. In his new book, The Case for Keto, Taubes discusses the potential benefits of the ketogenic diet, a lowcarbohydrate, high-fat diet that is being studied as a potential treatment for a range of diseases, from obesity and diabetes, to even cancer and Alzheimer’s.
You’ve long been one of the biggest advocates for the benefits of lowcarbohydrate, high-fat diets. How did this all begin? I did an investigative piece for the journal Scienceback in 2001 on dietary fat and heart disease. I interviewed around 140 researchers and administrators, and I concluded that there was never really compelling evidence for this low-fat diet we’d all been told to eat since the mid-1980s. When writing the story, I had a National Institute of Health administrator say to me: “When we told everyone to go on low-fat diets, we thought if nothing else they’d lose weight, because fat is the densest calorie in the diet. And instead they started eating more carbohydrates and everyone got fatter.” So I always had it my head that one of the main things that caused the obesity epidemic was this switch to a low-fat, high-carbohydrate diet.
In the book you point out that in 20 years, obesity and type 2 diabetes rates have doubled in the UK. Why do you think this has happened? We have this fundamental belief system about obesity, that it’s caused by caloric imbalance or overeating. So the idea is that we’re taking in more calories than we’re expending, and so the cure is to eat less, and reduce our calorie intake. I think that’s biologically naive, and rather than being about calories, obesity is actually a hormonal regulatory defect. The conventional approaches don’t work because while we can sustain eating less for a while, eventually the hunger gets us because we’re semi-starving ourselves. So, wrong approach – and when it fails, we blame the patients for not sustaining it.
The ketogenic diet is a widely accepted dietary treatment for epilepsy, but in your book you go further, describing it as a potential solution to the obesity epidemic and type 2 diabetes. What is the thinking for why a ketogenic diet can help in these cases? What I argue in the book is that obesity is not a caloric imbalance problem, it’s a hormonal regulation problem. Fat accumulation is primarily regulated by the hormone insulin, and the idea is that for those who are obese, diabetic, or predisposed, they have to minimise their insulin levels to solve the problem. By restricting carbohydrate, the ketogenic diet minimises insulin, and so instead of accumulating fat, your body starts mobilising it, and synthesising ketones out of it to use as fuel.
While there is some evidence that restricting carbohydrate intake can help obese patients, and those with type 2 diabetes, many doctors and nutrition experts feel that it remains relatively limited. What do we know so far? The most impressive research has been done by a Californian startup called Virta Health. They did a clinical trial at Indiana University where subjects either received conventional nutritional advice and medications, or a well formulated ketogenic diet. Over two years, the patients on the diet had remarkable results, effectively putting their diabetes in remission. The argument against this is that it wasn’t a randomised clinical trial, which would compare the ketogenic diet to other dietary therapies. But studies like this are causing a shift in the medical community, and people are embracing the idea that carbohydrates are fattening. As an example, there’s a Facebook group of female physicians in Canada, eating low-carbohydrate, high-fat diets for their weight, and there’s 4,000 of them in this group, which equates to around one in 10 female physicians in Canada.
One of the main criticisms of the science around the ketogenic diet is that most of the studies are only shortterm, for a couple of months, and the diets are often poorly defined. Do we need better quality data? In an ideal world, the diabetes and the obesity research communities would say: “Between us, it’s costing over $1bn a day in direct medical care in the US, and if we spent one day’s worth of these costs doing rigorous clinical trials of different diets, we might learn enough to save trillions of dollars down the line.” Ideally, we would have a trial involving several tens of thousands of people on the spectrum from overweight to obese, and pre-diabetic to diabetics. You could compare four diets, for example the ketogenic diet, vegetarian/ vegan, Mediterranean, and the Dash diet, and then follow them for three years minimum. It would cost in the region of $20-30m, but it would hopefully tell you which diet helps people live longer.
There are some scientists looking at whether ketogenic diets could be an adjuvant cancer therapy, sensitising tumours to treatment, and in 2020 a study came out suggesting that low-carbohydrate diets may help prevent age-related damage to the brain. What do you think about this research? The cancer research makes a lot of sense, that tumours rely on us gobbling down blood sugar. There’s always been evidence that if you increase insulin, you can stimulate tumour growth. This would explain the increased cancer rates in populations when they transition to western diets, and begin to manifest obesity and diabetes. But it’s still a hypothesis, and we need more clinical evidence proving that these diets can help. At the moment there are 262 clinical trials running, looking at ketogenic diets for everything from Alzheimer’s disease to traumatic brain injury. If more of these studies start showing benefit, I think it will shift people’s thinking.
One of the common criticisms often levelled at the ketogenic diet is that it’s too restrictive (with less than 50g of carbohydrate a day). Is it a practical long-term solution? If you’ve got a medical problem that might be diet-related, then it makes sense to see if you can find what foods are triggering it and what not to eat so you don’t have to live with that problem. I have a friend I met while researching this book, who comes from a family with a history of obesity, and weighed 400lb (28st 8lb/181.4kg) at age 18. He had never walked away from a meal not still hungry until he started the ketogenic diet. He lost 130lb (59kg) in four months, and the last time I saw him, he weighed about 230lb (104.3kg). So for people who lose 150lb on the diet, get to be lean, mean, and eat to satiety – for them, it’s not too restrictive. For other people, maybe it is.
The ketogenic diet typically involves eating a higher protein intake. As it’s been gaining in popularity in recent years, so too has veganism, which has the opposite paradigm. What is your perspective? The vegan diet does worry me because there’s another fundamental principle here, which is that we should eat what we have evolved to eat, and no human population has ever evolved to be vegan. If they had animal products available, they consumed them, which would suggest that there are reasons to consume animal products and not only plants, which go beyond gastronomic preferences. But if someone’s struggling with their weight, or is becoming diabetic, they could certainly try a vegan or a vegetarian diet. If they get healthier, then great, but if they don’t get healthier and they don’t have ethical issues with eating animals, then ideally they would say, perhaps I should try this carbohydrate-restricted diet with animal products.
• The Case for Keto by Gary Taubes is published by Granta (£14.99). To order a copy go to guardianbookshop.com. Delivery charges may apply