Even True Believers Need a Control Group
Sigh. A previously published study – which lacks a control group – is cropping up in a new form to beat the drum of claims that sugar is toxic. Based on a dataset published last year in Obesity, a new publication has just appeared in Atherosclerosis. The first publication from this dataset advanced a claim that holding calories constant while restricting fructose improved metabolic function in children with obesity. In this new publication, the authors report on markers of dyslipidemia and cardiovascular disease risk.
In a letter to the editor published in February, Tauseef Khan and John Sievenpiper explained a key problem with the original study:
It was an uncontrolled before-after study in which children’s baseline self-reported diet, which can be inaccurate, was contrasted to a low-sugar diet provided for 9 days. It is likely that lifestyle and eating behaviors other than sugar intake changed.
What this means is that we now have two publications of one uncontrolled study of fructose restriction.
The problem with this data is that the premise of the study – isocaloric fructose restriction – is not exactly accurate. The authors are claiming that they matched the calories that children consumed during the experiment with fructose to the calories the children consumed before the experiment.
In fact they matched the calories that the children reported consuming. The authors noted the reason this can be a problem in their first publication, saying “recall bias underestimating sugar consumption is the norm in epidemiological studies.”
But then they ignored the issue and continued to claim that they held calories constant during the fructose restriction.
Setting up a valid control group for a study can be a real nuisance. But without well-controlled studies, claims about dramatic benefits from restricting sugar consumption are not valid.
Overstated claims have a way of causing trouble down the road.
Click here for the publication in Atherosclerosis, here for the publication in Obesity, and here for more perspective on problems with this dataset. Click here for perspective on potential problems with multiple publications from the same study.
Connoisseurs Of Books (Knowledge Is Power), painting by Nikolay Bogdanov-Belsky via WikiArt
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July 25, 2016
July 25, 2016 at 8:57 am, David Brown said:
Excerpt from New York Times article on primate obesity research:
Dr. Grove and researchers at some other centers say the high-fructose corn syrup appears to accelerate the development of obesity and diabetes. “It wasn’t until we added those carbs that we got all those other changes, including those changes in body fat,” said Anthony G. Comuzzie, who helped create an obese baboon colony at the Southwest National Primate Research Center in San Antonio. Still, about 40 percent do not put on a lot of weight. Barbara C. Hansen of the University of South Florida said calories, but not high fat, were important. “To suggest that humans and monkeys get fat because of a high-fat diet is not a good suggestion,” she said. Dr. Hansen, who has been doing research on obese monkeys for four decades, prefers animals that become naturally obese with age, just as many humans do. Fat Albert, one of her monkeys who she said was at one time the world’s heaviest rhesus, at 70 pounds, ate “nothing but an American Heart Association-recommended diet,” she said. http://www.nytimes.com/2011/02/20/health/20monkey.html?_r=0
Research on humans published in 1967:
Controlled metabolic studies including periods of intersubstitution of sugar (mainly sucrose) and starch in the diet were made in a series of patients with carbohydrate-induced hyperglyceridemia. Sugar feeding markedly exaggerated the hyperglyceridemia in all of the patients studied. Equicaloric substitution of starch for sugar in the diet resulted in lowering of the elevated serum lipids toward normal. It was necessary to raise the daily carbohydrate intake to 85-90% of the total daily caloric intake in order to induce hyperglyceridemia in normolipemic subjects.
http://ajcn.nutrition.org/content/20/2/116.abstract
My take on these matters:
The sugar interests maintain that sugar is not uniquely fattening, which is true. But carbohydrate sensitive individuals have a problem with high sugar intake so reducing carbohydrate intake in general and added sugars in particular is important for weight loss for a substantial portion of the population.
July 25, 2016 at 11:08 am, Allen Browne said:
One size does not fit all.
July 26, 2016 at 3:40 am, Mary-Jo Overwater said:
Cherry-picking methods as well as data, we know, is dangerous. What’s even more dangerous is the poor peer-reviewing going on here and the cherry-picking occurring in publishing this work — twice. Conclusions and ensuing headlines can have an effect on public policy, manufacturing practices, costs to manufacturers, and ultimately, consumers, and nutritional status of populations. I’m all for making changes that improve and help all those stakeholders, but better and sounder reasons must be the foundation for all the hard work, endless long hours, and multi-millions of dollars that will go into making changes that such research purports will improve endgames for all stakeholders.
July 26, 2016 at 4:30 am, Ted said:
Well said, Mary-Jo.