Has the low-carb, Banting bubble finally burst?

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Are low-carb foods on their way out?

By Marika Sboros

The low-carb, high-fat (LCHF) bubble appears finally to have burst. A new study shows that doctors and  dietitians who say LCHF is a passing fad have been right all long. Carbs are fine even if you are obese as long as you keep fat low in your diet.

You might even believe that if you buy into findings of a study presented by US metabolism specialist Dr Kevin Hall at the International Obesity Congress held in Vancouver Canada earlier this month.

Hall has participated in studies in the past hinting at mortal wounding of the carb-insulin hypothesis of obesity including a study in the journal, Cell Metabolism, in 2015. Now he says his new research delivers the terminal blow.

Other doctors and scientists say: Not so fast. Hall is premature in declaring the death of the carb-insulin hypothesis. US physician Dr Michael Eades, a world authority on LCHF, goes further and says Hall may be “going rogue” and has “done something extremely bizarre” …

Eades says Hall has “misrepresented” his own data for his own ends.

Experts in metabolism and low-carb diets say you’re far better off instead sticking to compelling evidence showing that LCHF is neither dangerous nor a fad; that it is safe and effective not just for weight loss but to reverse life-threatening diseases millions of people have developed after decades of eating according to  conventional, high-carb, low-fat (HCLF) “wisdom” and the official dietary guidelines drawn up based on that paradigm.

But what’s really behind this latest attempt to discredit the science behind low-carb regimens and provide not-so-covert support for conventional dietary dogma for weight loss and obesity?

Dr Kevin Hall

Dr Kevin Hall

Hall, a researcher in the US National Institute of Health’s National Institute of Diabetes and Digestive and Kidney Diseases, gives the background  in a short interview with Canadian family physician and University of Ottawa assistant professor Dr Yoni Freedhoff  available on YouTube (to watch the video, scroll down below).

He describes the study design: the researchers closely monitored and controlled 17 obese men for two days a week for two months inside a closed metabolic chamber, and  compared the metabolic effects of  a conventional diet with carbs and low in fat with  a ketogenic LCHF diet of 80% fat and just 5% carbs.

Among other findings, Hall says fat loss slowed down on the ketogenic diet, and it took the full 28 days of a ketogenic diet to achieve the same amount of fat loss as the normal carbohydrate diet achieved in the first 15 days.

The findings showed no “metabolic advantage” to a “ketogenic” low-carb diet compared with a conventional diet. Thus the study “falsifies” the carb-insulin hypothesis.

That’s scientific music to ears of doctors and dietitians who insist that LCHF is dangerous and unsustainable and that HCLF diets are best for weight loss. They say this despite mounting evidence on the effects on people’s health after decades of HCLF eating: global epidemics of obesity, diabetes, heart disease, even dementia, which some doctors now call type 3 diabetes because of its links with diet.


Even  Freedhoff, who puts patients onto low-carb diets and has been highly critical of badly designed studies suggesting low-carb diets are dangerous, believes that Hall’s study has “absolutely debunked carb/insulin hypothesis tenets”.

That’s a rarity, he  says, because study designs don’t usually allow for researchers to use words like “falsified”.

Dr Richard Feinman

Dr Richard Feinman

US specialist Dr Richard Feinman, professor of cell biology at SUNY (State University of New York), is not so sanguine. He is “battling to understand all the hoopla” about Hall’s study:

“They showed a metabolic advantage. Right? There seems to be little appreciation of what the logic of metabolic advantage is.

“Nobody says it always happens, or happens to any particular level. Just the opposite.”

Most of the time “a calorie is a calorie”, says Feinman, because metabolism is connected in feedback and unless you break through the steady-state you won’t see big changes. The question is whether there is anybody, even one person, who does not show this, one black swan – of any size.

“Once you know it is possible, once you see it can happen at all, then you can try to maximise the effects,” he says.

Even if, as people seem to be saying about Hall’s experiment,  it is all white swans (difficult to say as all the data have not yet been seen),  then “you haven’t shown anything at all”. Feinman says.

“It’s only news if you find a black swan”, he says.

There may actually be some black swans in there as Hall has only reported group data. But Feinman says the study does “not seem to be a  well-conceived experiment” and  once you step out of the metabolic chamber you are “back to dietary records”. It is also not  appropriately reported, although “we may learn more if it actually undergoes peer review”.

He finds the study “strangely anachronistic”: He and others have explained how there is no physical barrier and, in fact, thermodynamics “more or less predicts big variability in metabolic efficiency”. It has been shown in animal studies and in physiologic studies demonstrating thermic effect of feeding, inefficiency due to substrate cycling and in human diet studies where the changes are sufficiently large that they are unlikely due to experimental error.


Overall, Feinman says most people know that the “best bet is low-carb for weight loss, diabetes and metabolic syndrome”. Others diets work but are weaker and the progression of Mediterranean, Nordic, low-GI diets “are mostly a way of saving face”.

And of course, there’s always the  Brooklyn Diet , Feinman says. (He meant it as a joke, I Googled it and found a book of the same name, subtitled Life’s tough but you eat anyway: A Conversation with Sam Bloom and Al Johnsen.)

Eades has written a scathing blog on the topic. In it takes his usual surgical scalpel to dissect and expose what look suspiciously like terminal flaws in Hall’s video presentation of the study (it’s a long  but fascinating read; scroll down for a link to the full blog).

Dr Michael Eades

Dr Michael Eades

Eades explains metabolic advantage  in detail, and reminds readers that it is “an effect, not a cause”.

He says Hall probably has a bad case of “cognitive dissonance” – the psychological term for the discomfort that arises when evidence contradicts a passionately held belief, and that  leads to the evidence being ignored in favour of belief.

One sign is there  “right off the bat” in the title of the study alone, says Eades: Energy Expenditure Increases Following An Isocaloric Ketogenic Diet In Overweight And Obese Men.

“How can Hall say the data from this experiment produced no metabolic advantage when the title of his paper says the opposite? Good question.”

The study has many other “oops” factors, elements that Hall has difficulty explaining, says Eades that make it a “very sloppy study”. For example, the participants spent five days per week spent outside the chamber during which they were fed 500 fewer calories than required for their weight maintenance and energy balance.

The study also appears to have been a pilot. Eades says the word “pilot” implies that the researchers “knew there would be inherent limitations when they started it”.  Right there, that left him wondering why Hall has “such confidence about what he thinks he’s proven”.

Hall creates the impression in the video that this was his study, but Eades says it was actually a collaboration with very senior researchers  at Columbia University, Pennington Biomedical Research Center in Baton Rouge and the Translational Research Institute for Metabolism and Diabetes in Orlando.

 Hall may be “taking the opportunity to say something publicly that his older and presumably wiser colleagues wouldn’t agree with”, says Eades. What Hall says in the video bears “little resemblance” to the official abstract published in the Vancouver World Obesity Congress program.

Eades is clear on what he believes is driving Hall: “If you spent 15 years of your academic career insisting that a calorie is a calorie, would you like to publish a study with strong data more or less negating what you’ve been saying all your working life? Especially if you had publicly ridiculed that philosophy in years gone by?

“If you were Kevin Hall and you spent the last year insisting that low-fat diets were the best way to lose weight and that you’d already refuted the carbohydrate-insulin hypothesis, wouldn’t you be tempted to spin your data to suggest that you’re still right?”

The widespread response to the video seems to be nothing more than “an ink blot test separating those who believe there is a metabolic advantage with a low-carb or ketogenic diet and those who don’t”.

Hall’s interview is one reason journals “don’t like scientists to talk about results before they publish the paper”, Eades says:

“Without the paper, none of us can tell if the scientist is spinning the data to satisfy some pet agenda. Gullible folks on the internet and in the press can then take it and run, which is what happened here.”

  • Dr Kevin Hall has been invited to respond via email.