A diet book developed by researchers at Australia's largest government laboratory network has already made the organization more than A$1.5 million (US$1.1 million) in royalties. But its success is feeding a growing body of critics who say that its high-protein message is not supported by the evidence. They also question the influence of the meat industry, which sponsored it.

“It's far more successful than we ever anticipated,” says Manny Noakes of the Commonwealth Scientific and Industrial Research Organization (CSIRO) in Adelaide, who wrote The CSIRO Total Wellbeing Diet with her colleague Peter Clifton.

Manny Noakes (left) co-authored a book that advocates eating more protein for weight loss. Credit: AAP/A. PORRITT

The book has become a national bestseller, having sold nearly half a million copies since its launch in May. It went on sale in Britain in September, with release in further countries, including the United States, planned for 2006. Its recommendations even feature on the menu at Australia's Parliament House.

But critics have spoken out about the possible influence of the Australian meat and livestock industry, which funded a large portion of the research behind the high-protein diet. “There is a bias towards the sponsor's product which is not justified by the results of their research,” says Rosemary Stanton, a nutritionist and visiting fellow at the University of New South Wales in Sydney.

The diet advocates a much higher protein intake than that recommended by most national guidelines. People on a typical Western diet obtain about 15% of their energy intake as protein, but the CSIRO diet recommends doubling that to 30–35% while reducing carbohydrate intake. To achieve this, Noakes and Clifton suggest eating more meat and fish at lunch and dinner.

“You have to ask why they didn't promote more plant-based proteins,” says Stanton. “Did their choice of protein come about because of the sponsor?” The authors insist that the industrial sponsors were kept at arm's length. “They didn't have any impact on the design of the study and how we interpreted the results,” says Clifton.

Nonetheless, Meat and Livestock Australia, which represents the nation's livestock industry, has been a keen publicist: it distributed a booklet on the diet in a women's magazine. This was noticed by the publisher Penguin, which then commissioned the book. Royalties go to CSIRO nutrition research.

Other scientists are concerned that the evidence behind the diet is weak, and that by putting its name to the book the CSIRO is giving the diet unwarranted credibility. “The CSIRO name unquestionably sells more copies,” says Jim Mann, a nutrition expert at the University of Otago in Dunedin, New Zealand. “But the hype goes beyond what the research proves.”

“The main trial showed no difference in weight loss compared with a conventional diet,” points out Patrick Holford, founder of the Institute for Optimum Nutrition based near London, UK. He believes that sticking to such a diet could elevate the risks of breast and prostate cancer, stress the kidneys and adversely affect bone mass. “I think it is dangerous long-term,” he says.

The authors based the diet on several studies, the largest being their own trial of 100 overweight women over 12 weeks (M. Noakes et al. Am. J. Clin. Nutr. 81, 1298–1306; 2005). Half the women were given a high-protein diet and the other half a high-carbohydrate diet. Both diets contained the same number of calories, and both groups of women lost the same amount of weight. But the authors say their recommendations are valid because women with high triglyceride levels — a marker of insulin resistance — shed significantly more weight on the high-protein diet. Participants were also more likely to stick with the high-protein diet.

The CSIRO stands by its decision to commercialize the research. “The CSIRO has always published books on its scientific work and put its name to publications, and this is no exception,” says a spokeswoman. “The decision to publish was in response to many consumers asking for further details of the diet.”