Mark A. Pereira's Research

Effects of Dietary Composition on Exercise Tolerance in Obese Adults

Principal Investigator: Mark A. Pereira
Investigators: Mark Pereira, PH.D. (PI), Susan Raatz, Ph.D., Bruce Redmon, Ph.D., Alexander Rothman, Ph.D., Donald Dengel, Ph.D.
Funding Agency: American Heart Association
We believe people??s physiological responses to exercise have an important systematic influence on their psychological response to exercise, which we refer to as ??exercise tolerance??. We theorize that the composition of the diet may affect exercise tolerance through its known impact on metabolic fuels (i.e. glucose and fatty acid. Specifically, typical high carbohydrate diets may have a deleterious impact on exercise tolerance through effects of postprandial hyperinsulinemia on the partitioning of metabolic fuels from oxidation to storage. Our research has shown that high carbohydrate diets, relative to energy-matched moderate carbohydrate diets, result in reactive hypoglycemia, an augmented drop in resting energy expenditure during weight loss, and greater perceived hunger. We theorize that the proposed interplay between the physiological and the psychological systems may have implications for the maintenance of a physically active lifestyle. To this end, we will use a randomized cross-over design to compare the effects of two dietary patterns ?C Control (high carbohydrate) v. Experimental (lower in carbohydrate, more slowly digested carbohydrates) -- on obese individuals. A second version of the Experimental diet will be high in protein. Specifically, we will examine the relative effect of the diets on metabolic fuels during standardized exercise testing; perceived exertion, energy, and mood during standardized exercise testing; and free-living day-to-day reported energy levels, mood, and well-being. By addressing these aims, the proposed study will contribute to our understanding of the interplay between the physiological and psychological systems that regulate people??s exercise behavior. Moreover, if the composition of the diet is shown to have a causal influence on exercise physiology and, in turn, on how people think and feel about exercise, it will provide the basis for new directions in the design of interventions to promote physical activity and prevent obesity.

Genetic and Environmental Determinants of Type 2 Diabetes in Singaporean Chinese

Principal Investigator: Mark A. Pereira
Investigators: Mark Pereira (PI), Myron Gross (Co-PI), Jian-Min Yuan, Andrew Odegaard
Funding Agency: National Institutes of Health / NIDDK
Southeast Asian populations have high rates of type 2 diabetes (T2D) despite low rates of obesity. This ??Southeast Asian Paradox?? has caused an extremely high public health and economic burden. While Southeast Asian-specific lower thresholds for defining obesity, set by the World Health Organization, underscore the particular susceptibility of these ethnic groups to T2D, the underlying biological and environmental causes for the excess diabetes in these populations are unknown. To date, genome-wide association studies of T2D have been completed in European populations, with none in other ethnic groups. These recent genetic findings only add to a ??Southeast Asian Paradox?? of T2D because several of the risk alleles found in Europeans have relatively low frequencies in the Asians. Our main aim is the identification of genetic susceptibility factors for T2D in Chinese living in Singapore, where there is a high prevalence of T2D. The study samples are derived from the ongoing Singapore Chinese Health Study, a population-based prospective cohort of 63,257 adult men and women assembled during 1993-1998 and continuously followed to date for incident morbidity and mortality. The NIH has been supporting the Singapore Chinese Health Study since its inception. There has been and continues to be significant cost-sharing by the National University of Singapore. All biological samples have already been collected and are ready for genotyping, and all environmental factors have been collected at baseline prior to the accrual of incident diabetes cases. Thus, we are in a unique position of conducting a genome-wide association study like none other to date in the following respects: 1) Very large size ?C 6,132 cases and 6,132 controls; 2) Nested case-control design ?C allowing for gene x environment interactions; 3) Unique, high risk population for which we currently have a weak understanding of T2DM etiology; 4) Extensive cost-sharing by the Genome Institute of Singapore and National University of Singapore, resulting in a high ratio of scientific discovery to monetary cost; and 5) Replication of our findings in two external Asian cohort studies. We believe the study proposed in this application will move the field forward in understanding the biological and environmental determinants of T2D in many Asian populations, and improve risk stratification so that those at greatest risk can be identified for early prevention or treatment.

Physiological and Behavioral Effects of Sit-Stand Workstations: A Randomized Controlled Trial

Principal Investigator: Mark A. Pereira
Investigators: Nirjhar Dutta, Steven Stovitz
Funding Agency: University of Minnesota and The Mayo Clinic

We are conducting a worksite intervention study to evaluate the impact of increasing standing time at work in sedentary office workers in a local Minneapolis business.  Using a randomized cross-over design, the participants will switch from a mostly sitting workday to approximately half sitting and half standing.  For the sit-stand intervention, workstations are being installed in each employee’s computer desk work area.  These desks are adjustable to make the change from sitting to standing, and from standing to sitting, very easy.  The intervention and control periods are one month each, with a one month washout period.  A number of relevant behavioral, psychological, and physiological outcomes will be tested to identify potential benefits

Television Viewing and Risk of Injury and Chronic Disease Morbidity

Principal Investigator: Mark A. Pereira
Investigators: Mark Pereira (PI), Darin Erickson, David Jacobs, Anthony Fabio (PI at University of Pittsburgh)
Funding Agency: National Institutes of Health / National Institute of Aging
The CARDIA Study data will be used to evaluate the propensity that television exposure may increase the risk for intentional and unintentional injuries, as well as obesity and chronic diseases through a variety of plausible and interrelated mechanisms. We aim to explore the possibility of an interaction between televesion viewing and the hostility trait in predicting a variatey of important health outcomes over this large 20-year prospective study in Caucasians and African Americans from the four U.S. metrapolitan areas.