Should low-carb, high fat diets be considered “fad diets”? A Comment by Mann and Nye published in the Lancet simply assumes that these diets don’t have any scientific credibility, but we’ve seen a number of important studies in major publications, including recent trials in the NEJM by Shai et al and in JAMA, by Gardner et al, to suggest that these diets are very far from being dismissed as mere fads. In fact, there’s plenty of evidence to suggest that they should be taken very seriously indeed. (In fact, as any expert will reluctantly concede, there’s almost no good randomized, controlled data to conclusively demonstrate that any diet is better than any other.)
It’s important that real fads be exposed for what they truly are, but it’s equally important that genuine alternative hypotheses don’t get branded as marginal simply because they don’t conform to conventional wisdom.
Here is the Lancet press release:
FAD DIETS IN SWEDEN, OF ALL PLACES
Nutrition experts have expressed their surprise over the involvement of Sweden in a controversy regarding promotion of low carbohydrate high fat (LCHF) diets in the country. The issues are discussed in a Comment published in this week’s edition of The Lancet, written by Dr Jim Mann and Dr Edwin R Nye, University of Otago, Dunedin, New Zealand.
Many ‘fad’ diets have been publicised in recent years, including the ultra-low carbohydrate Atkins diet. Other comparable LCHF diets have also been credited with significant weight loss without obvious adverse effects. The authors say: “Most authorities have argued against prescription of LCHF diets and such messages have not been incorporated into dietary guidelines for populations and people with diabetes. However, recent experiences in Sweden show the potential of committed adherents, supported by a potentially misguided mass media, to influence officialdom to an extent that might adversely influence national public health and the health of individuals.”
The controversy began in 2007 when two dietitians suggested to Sweden’s National Board of Health and Welfare that LCHF dietary advice recommended to diabetic patients by general practitioner Dr Annika Dahlqvist was not compatible with either scientific evidence or accepted practice. However, Dahlqvist was exonerated after a report by diabetologist Dr Christian Berne, who said there was some scientific basis for offering LCHF diets, with a number of caveats—including the absence of long-term studies and the need for patient monitoring (including measurement of lipids). Dahlqvist’s exoneration resulted in headlines suggesting an about-turn by the Board, and Dahlqvist herself suggested that her diet was appropriate not only for people with diabetes but also for the whole population for better health and weight control.
Another facet to the story then emerged. An expert group, part of the Board, had been due to publish a report on nutritional recommendations for people with diabetes. But two of the experts on the panel were removed by the newly appointed Director-General—who considered their links to the food industry via the Swedish Nutrition Foundation might represent a conflict of interest. The Foundation receives food industry funding—but via expert scientists provides independent advice to industry. The two scientists involved—Bengt Vessby and Nils-Georg Asp, are internationally respected, and their dismissal caused outrage in the rest of the Board and the scientific community. The expert group began work in September 2008, but in the meantime the authors say that ‘misguided enthusiasm and reporting appear to have triumphed over expert opinion’. Aftonbladet, the country’s largest newspaper, has published details of high fat/low carbohydrate principle. An anonymous letter, quoting Dahlqvist’s blogs, has been sent to all schools, preschools, and daycare centres in the country, advocating this dietary approach to ‘save our children’s brains’. The authors say: “Despite the National Food Administration of Sweden having
published a list of 72 articles which suggest that high fat diets are detrimental compared with eight articles suggesting that they are not, enthusiasm for high-fat diets persists. One of Dahlqvist’s popular books on the subject of high-fat diets has been number one on the non-fiction bestseller list in Sweden.”
The authors believe it likely the Swedish public will interpret the sequence of events as another example of experts failing to agree, and that they will conclude there is no case for making dietary changes associated with clinical and public health benefit (ie, to lower-fat diets). They say: “It is also ironic that this debate should have occurred in a country which helped to pioneer cardiac rehabilitation and preventive cardiology, and one of the few to report a decline in the rates of childhood obesity.”
They conclude: “There are some lessons here for international agencies, professional organisations, and governmental and regulatory bodies. Perhaps one of the most important is the need for internationally accepted criteria for evidence-based nutrition guidelines as there are for evidence-based medicine.”