Angelo Tremblay on the Environmental Risk Factors for Obesity

Special Topic Interview, August 2010

Angelo TremblayIn our Special Topics analysis of obesity research over the past decade, the work of Dr. Angelo Tremblay ranks at #4 by total papers, based on 171 papers cited 2,664 times. His record in Essential Science IndicatorsSM from Thomson Reuters includes 290 papers, the majority of which are classified under Clinical Medicine or Biology & Biochemistry, cited a total of 3,898 times between January 1, 2000 and April 30, 2010.

Tremblay is a professor in the Department of Social and Preventive Medicine at Laval University in Quebec, Canada. He also holds a Canada Research Chair in Environment and Energy Balance. correspondent Gary Taubes talks with him about his obesity-related research.

SW: When did you start your research into the obesity and what role did the Quebec Family Study play?

My first very significant move toward research was early in 1977, when I went to see Claude Bouchard, coming back from his doctoral studies in Austin, Texas. He was intent on starting the population study that became the Quebec Family Study, and I offered him my collaboration. Since then we have worked on three phases of this study, covering more than 20 years.

SW: The Quebec Family Study ran for two decades. Can you tell us the general outline of the study?

Phase one began in 1978 and ran to 1982 and included 375 families. It gave us the opportunity to make some methodological contributions and to perform epidemiological studies. We also took advantage of the family design of the study to initiate our research on the genetics of obesity—to look at family resemblance for different traits, including obesity phenotypes.

The second phase began in 1989 and went to 1997. We had fewer families, but more variables, more markers, and we incorporated in the cohort a subpopulation of obese individuals, recruited specifically because of their obesity. Phase three of the study began in 1998, and by its end included more than 500 families and 2,000 subjects.

SW: What do you consider the major contributions of the study to obesity research?

I would say that one major contribution of the Quebec Family Study has been its extensive documentation of environmental and genetic markers that predict the risk of obesity and the establishment, to some extent, of a hierarchy of their importance. We discussed this in a recent paper published in Obesity, Chaput et al. ("Risk Factors for Adult Overweight and Obesity in the Quebec Family Study: Have We Been Barking Up the Wrong Tree?" 17: 1964-70, 2009).

"...we looked at dairy consumption and found that low consumers, particularly females, were more prone to high body fat."

This was done using the six-year follow-up between phase two and three of the study. We documented the importance of short sleep duration, dietary restraint, dietary disinhibition, low calcium intake, low participation in vigorous physical activity, low vitamin intake, high fat diet, and high alcohol consumption. To my knowledge no other study has documented the relative importance of these different environmental factors in terms of their predictability of overweight.

SW: Which factor turned out to be the best predictor of future obesity?

Surprisingly, short sleep duration. After that came high disinhibition and also low calcium intake. The latter was originally published in 2003 in the American Journal of Clinical Nutrition, Jacqmain et al., and it's now our highest cited paper from the last decade ("Calcium intake, body composition, and lipoprotein-lipid concentrations in adults," 77: 1448-52, 2003).

SW: What prompted you to measure calcium intake in the first place? How did that hypothesis come about?

The idea to focus on calcium, both for us and other investigators, was a paper published by Michael Zemel and his collaborators in 2000. That was the source of inspiration, although this was not a new story at that time. In the 1980s David McCarron began looking at the role of calcium but nobody paid much attention to his observations.

In fact the Zemel paper was a study in African American subjects given a yogurt intervention for a year. Zemel told me that he had these results in 1988 and waited for 12 years before publishing them, because he didn't know what exactly to say about them. When he did publish in 2000, we went back to our database to look at what the Quebec Family Study could say about it, and the result was this Jacqmain paper.

SW: What are sources of calcium in the diet other than dairy products?

We were looking at dairy products, which our data suggested made up about 60-65% of calcium intake. We also get a little bit of calcium from some meats like salmon; a little from some vegetables, but what we found is what other studies have also found, that the most calcium by far is provided by dairy foods.

Without dairy foods in the diet, it's difficult to have an adequate intake. So we looked at dairy consumption and found that low consumers, particularly females, were more prone to high body fat.

SW: Are you surprised this paper has been so influential and highly cited?

Not so much, because the timing was right. After Zemel published his paper, other research teams took two to three years to react as well. Our paper was one of the first to provide convincing support to Zemel's observation, so it's been cited frequently in support of it.

I have to say that we also reported another finding in this paper that has not been reproduced consistently by others—that was the link between blood lipids and calcium intake, independent of the association between calcium and body fat and waist circumference.

Subsequently we were able to confirm blood lipid association in a clinical trial that we published in the American Journal of Clinical Nutrition in 2007 (Major GC, et al., "Supplementation with calcium plus vitamin D enhances the beneficial effect of weight loss on plasma lipid and lipoprotein concentrations," 85: 54-9, 2007).

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