Dr. Shephard was a medical physician with extensive training in exercise science and public health (Archer and Blair 2011). He understood the distinct language and research cultures of physicians and exercise scientists that largely operated in silos, and encouraged cross-disciplinary communication between these fields.
As early as the 1960s, Dr. Shephard began to write about the harmful effect of physical inactivity and was among the first to establish a link between physical inactivity and cardiovascular health. His work was instrumental in helping physicians and the public understand that the dangers of exercising were dwarfed by the much larger risk of not exercising for ill health (Shephard 1986). His early work (Shephard 1967), lay the framework for the first sedentary guidelines that were spearheaded by Dr. Mark Tremblay (CHEO) in 2012. Currently, Canada is a world leader in highlighting the health detriments of sedentary behavior and the creation of Physical Activity Report Cards for Children and Youth (Participaction 2016), which are now emulated in dozens of countries around the globe. Dr. Tremblay along with Jean-Philippe Chaput and Valerie Carson have recently created the world’s first 24-Hour Movement Guidelines for Children and Youth (Tremblay et al. 2016).
These guidelines would not have been possible if not for the basic and clinical research done by Canadian researchers that have contributed to our understanding of how physical activity, relates to metabolic health and obesity. This review will focus on the Canadian research contributions to the areas of body composition and health risk assessment and clinical physical activity interventions for the improvement of cardiometabolic risk factors in humans.
Identification of High Risk Profiles
Over the last 50 years, the risk of obesity and its related comorbidities has been a focus for researchers and public health agencies. In particular, the assessment of body composition in which there have been several Canadian contributions. Dr. Michael Yuhaz from the University of Western Ontario published one of the early skinfold equations in 1974 which is still used by many researchers and Kinesiology programs around the world for the determination of percent body fat (Yuhaz 1974). Starting in the late 1980s, Drs. Claude Bouchard, Angelo Tremblay and Jean-Pierre Després from Laval University helped identify the importance of fat distribution in how obesity relates to cardiometabolic risk (Després et al. 1985), and the importance of genetics in determining fat distribution (Bouchard et al 1988; Rankinen et al. 2006). This work highlighted the detrimental effects of abdominal obesity in diabetes and CVD risk. Drs. Norman Gledhill and. Roni Jamnik from York University used this work to develop obesity-health risk algorithms that were uniquely distinct from fitness and performance related algorithms that were presented in 1988 at the “International Conference on Exercise, Fitness and Health” and ultimately published in CSEP’s Canadian Physical Activity, Fitness and Lifestyle Appraisal manual in 1996 that has been used in Kinesiology programs throughout Canada and the world.
In the late 1980s, Dr. Després (1989) began using computed tomography to show the deleterious association between abdominal fat distribution and cardiometabolic risk, and in the early 1990s (Després et al. 1990), Dr. Robert Ross from Queen’s University was one of the leaders in applying magnetic resonance imaging to assess whole body composition and the measurement of visceral fat (Ross et al. 1992). Multi-cultural Community Health Assessment Trial (M-CHAT) spearheaded by Dr. Scott Lear (Simon Fraser University) has extended this work to show ethnic differences in visceral fat between Whites, South Asians, East Asians and Aboriginal ethnic minority groups, and ethnic differences in how obesity relates to health (Lear et al. 2007). Despite a proliferation of research during this time showing that visceral fat was one of the strongest independent body compositional measures of metabolic disorders, it wasn’t till 2006 when the first study showing visceral fat to be an independent predictor of mortality was published by Canadian researchers (Drs. Jennifer Kuk and Robert Ross, Queen’s University). The second report published by a Canadian researcher Dr. Peter Katzmarzyk in 2012 confirmed the importance of visceral obesity as a marker of mortality and remain the only two studies in the world on this important topic.
Because of the difficulty and expense of measuring visceral fat directly, much Canadian research has also focused on the more clinically useful measure of waist circumference which has repeatedly been shown to be the anthropometric measure more strongly associated with visceral fat (Lemieux et al. 1996; Pouliot et al. 1994). Drs. Ian Janssen and Peter Katzmarzyk at Queen’s University showed that waist circumference is useful in the prediction of health risk beyond body mass index alone. Dr. Salim Yusuf (McMaster University) echoed the importance of assessing abdominal obesity, particularly in other ethnic populations (Yusuf et al. 2005). Using decades of Canadian research, Dr. Després, proposed the “Hypertriglyceridemic Waist” as a marker of the Atherogenic Metabolic Triad differentiating individuals with obesity at elevated health risk (Lemieux et al. 2000). This paper has been cited over 500 times since its publication in 2000 and was one of the earlier risk algorithms to include waist circumference in the assessment of metabolic risk; earlier than the Metabolic Syndrome criteria published by the National Cholesterol Education Program (NCEP) in 2001.
Quebec Family Study established by Dr. Claude Bouchard at Laval University, is an observational study that has resulted in approximately 300 publications. This study has provided some of the earliest data on the genetic origins of obesity, lifestyle behaviours and metabolic disease. Some of the key findings from the Quebec Family Study have helped us to understand the significant contribution of genetics to the expression of obesity and diet and physical activity behaviours. This work was followed by Dr. Bouchard’s work in twins that illustrated that there are is a 3 fold variation in weight gain in response to a fixed over-consumption of calories while there were substantially less difference between monozygous twin pairs. The work of Bouchard and colleagues illustrates the importance of heritability characteristics in the development of obesity. In youth, Dr. Oded Bar-Or (McMaster University) was instrumental in our understanding of how lifestyle factors relate to obesity in youth (Bar-Or and Baranowski, 1994). Long before childhood obesity was in the spotlight, Dr. Bar-Or established the world’s first Children’s Exercise and Nutrition Centre at McMaster University in 1983, delivering an individualized nutrition and physical activity program for children with obesity.
Now we understand that the contributions to obesity extend far beyond simply diet and physical activity. Canadian researchers have improved our understanding and have identified factors such as intrauterine effects (Kristi Adamo – Ottawa University), sleep (JP Chaput – CHEO, Angelo Tremblay), non-caloric dietary factors such as calcium and vitamins (Angelo Tremblay, Rémi Rabasa-Lhoret,), organic pollutants (Pascal Imbeault, Eric Doucet, Angelo Tremblay), sedentary time (Mark Tremblay), weight cycling (Denis Prud’homme) to the development of obesity and metabolic disorders. In fact, many of these factors are shown to alter calorie management, metabolic efficiency and propensity to store adiposity tissue and thus alter obesity risk independent of the calories consumed and physical activity. In fact, Canadian researchers are among the world leaders in changing the way we think about obesity and whether or not you can be healthy but have obesity: e.g. metabolically healthy obesity (Caroline Kramer, Martin Brochu, Antony Karelis and Jennifer Kuk,). This area remains the subject of considerable debate with the causes and implications of this potentially unique obesity phenotype unclear. Given the unclear benefits of weight loss in these individuals with ‘healthy obesity’, Dr. Arya Sharma (U of Alberta) has proposed the Edmonton Obesity Staging System to better guide decision making in clinical practice.
Canadians have conducted several important clinical exercise trials that have shaped our understanding of how lifestyle factors relate to diabetes and cardiovascular disease risk factors and obesity. In the early 1970s, the Canadian government took interest in workplace wellness interventions that promised the benefit of decreased worker stress and increased productivity. Dr. Shephard was a leader in studying this novel approach of implementing physical activity intervention in the workplace. He understood the barriers to physical activity and recognized the importance of making physical activity accessible, convenient and the easy choice. Though this approach had not shown universal success in increasing physical activity or metabolic health, these studies have highlighted that increasing physical activity in a population is far more complex that was originally understood.
The HERITAGE study spearheaded by Dr. Claude Bouchard in the 1990s is a landmark study that included an international team of renowned researchers, resulting in over 200 publications to date. This work has highlighted the genetic influences on fitness and lipid responses to exercise training. There have also been several randomized controlled trials from Queen’s University (Robert Ross) and the University of Ottawa (Ron Sigal and Glenn Kenny) starting in the 1990s that have helped our understanding of how exercise type influences insulin sensitivity and body composition in youth and adults with obesity and or type 2 diabetes. Work from Queen’s university has clearly demonstrated that exercise can be associated with a reduction in visceral adiposity and improvements in metabolic health despite minimal or no weight loss. Work from these groups have demonstrated the benefits of aerobic and resistance exercise on the management of glucose are additive. Thus, both resistance and aerobic exercise are important for managing diabetes risk despite minimal weight loss. Over the last 10 years, there has been much interest in the potential health benefits of high intensity interval training and Martin Gibala (McMaster University) is at the forefront of examining its effectiveness and safety for improving cardiorespiratory fitness and health.
At the population level, Dr. Ron Plotnikoff (University of Alberta) has refined and applied individual- and environmental-level theory and interventions aimed at the prevention and management of diabetes and cardiovascular disease, as well as the promotion of healthy body weight and general health of the population through physical activity in various settings and sub-populations.
Clearly, Canadian researchers have had important contributions that have changed the way the world understands obesity and prevention of metabolic disorders using physical activity interventions over the last 50 years and we look forward to the next 50 years.
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