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International Health

Investigating the Causes and Consequences of Obesity
Associate Professor Youfa Wang

At the last faculty retreat, the Department’s commitment to emerging global health topics such as chronic disease, mental health, and injury prevention was debated. The consensus was that the Department should continue pursuing these research opportunities through collaborations within and outside the University. This spring, the JHSPH magazine highlighted work related to two of those topics with featured articles on the Department’s International Injury Research Unit (IIRU) and Applied Mental Health Research (AMHR) Group.

Associate Professor Youfa WangOne of the Department’s leaders on the chronic disease front, both in the US and abroad, has been Associate Professor Youfa Wang, MD, PhD. Over the last few years he has published several seminal papers on the epidemiology of obesity in US and global populations. He is currently leading several projects to investigate the causes of obesity, co-morbidities such as Type 2 diabetes, hypertension, and metabolic syndrome, as well as related interventions. His ongoing research is funded by grants from several agencies and foundations, including the NIH and US Department of Agriculture.

US and Global Obesity Trends:
Complicated Patterns

Most-cited article in Epidemiologic Review
Dr. Wang’s team has published several high-impact studies examining the epidemiology of obesity in the US and globally. His 2007 article on obesity in the US in the journal Epidemiologic Reviews is that journal’s most cited article since 2004. He and co-author May Beydoun—a former postdoctoral fellow at the School, now with the National Institute of Aging (NIA)—provided a comprehensive description of the trends and characteristics of the obesity epidemic in the US based on nationally representative data collected since the early 1970s. They illustrate how obesity levels have skyrocketed in nearly every population group in the US over the last three decades. Their findings also show how disproportionately affected minority and low-socioeconomic groups have been. (See, “The Obesity Epidemic in the United States—Gender, Age, Socioeconomic, Racial/Ethnic, and Geographic Characteristics: A Systematic Review and Meta-Regression Analysis.”)

Prevalence of obesity and overweight among US adults
US Obesity trends
Observed during 1976–2004 and projected. The projected prevalence presented here are those based on our linear regression models. (From Obesity (2008) 16 10, 2323–2330. doi:10.1038/oby.2008.351)

Capitol Hill and National Headlines
This year, Dr. Wang was invited to Capitol Hill to report on the US obesity epidemic and related financial consequences. His presentation to Congressional staff also addressed why health reform should contend with the obesity epidemic. His talk focused on the findings from his recent study entitled, “Will all Americans become overweight or obese? Estimating the progression and cost of the US obesity epidemic,” published in 2008 by the journal Obesity. The paper was co-authored by Drs. Benjamin Caballero and May Beydoun from the Department and Dr. Lan Liang from the US Agency for Healthcare Research and Quality, and Dr. Shiriki Kumanyika from the University of Pennsylvania School of Medicine.

Based on nationally representative survey data collected since the 1970s, they projected that if current trends continued, 86 percent of Americans would become obese or overweight in 2030. With that proportion of the population being overweight or obese, total related healthcare costs would be close to $900 billion. A number of domestic and international newspapers and TV news networks picked up on the article and reported widely on its findings. For just a couple examples, see the NY Times and
the ABC News story, America’s Waistline

Global Trends
Dr. Wang’s work has helped document the growing global obesity epidemic. Several of his studies have raised the awareness of this pressing issue among public health professionals, policymakers and the general public. Examples include a number of widely cited studies such as the 2002 article in American Journal of Clinical Nutrition, which has been cited over 500 times since its publication. The study examined the childhood obesity trends in four large countries on different continents. (See, “Trends of obesity and underweight in older children and adolescents in the United States, Brazil, China, and Russia.”) 

In collaboration with the International Obesity Taskforce (IOTF), he and co-author Dr. Tim Lobstein analyzed available data from over 50 countries and studied the changes over time in the prevalence of overweight and obesity in children and projected future levels. They showed that prevalence had increased in almost all countries for which trends data were available. Exceptions were found among school-age children in Russia and to some extent Poland during the 1990s, and among preschool children in some low-income countries. (See, Worldwide trends in childhood overweight and obesity. Int J Pediatr Obes. 2006;1(1):11-25.)

Annualized Change in Prevalence of Overweight and Obesity
in School-age Children in Survey since 1970 (percentage points)
Global Obesity Trends

Wang and Lobstein,
International Journal of Pediatric Obesity. 2006; 1: 11/25

* Self-reported data. Change in the combined prevalence of overweight and obesity among school-age children in surveys since 1970. The chart shows country, method of measurement and period of assessment for prevalence change. Methods of measurement: IOTF/International Obesity TaskForce recommended cut-off point for overweight, 85th and 90th/centiles for local or WHO BMI reference charts, 110%/percent of ideal body weight (locally defined).

Root Causes of Obesity and
Lifestyle-Related Chronic Disease

A focus of Dr. Wang’s work has been on the ethnic and economic disparities in obesity and their underlying causes. He recently won a $1.2 million NIH R01 grant to systematically investigate the individual-, family-, and community-level causes of ethnic and economic disparities in the rates of obesity and co-morbidities such as Type 2 diabetes and hypertension in the US.

Dr. Wang’s long-term research interest is to study the impact of childhood obesity and eating habits on the risk of chronic disease such as cardiovascular disease, type 2 diabetes and metabolic syndrome later in life, and how appropriate interventions may help prevent such health conditions. He is tracking health-related behaviors, such as eating and exercise habits, and health outcomes, such as blood pressure from childhood to adulthood. Moreover, he is investigating how family environment and parental factors may affect children’s health and related behaviors, with the goal of developing effective intervention programs in the future. Some of these studies are based on data collected from large national surveys and cohorts in the US and China. For example, in China, he and local collaborators are attempting to pinpoint the root causes of chronic disease, such as hypertension and metabolic syndrome in children and adults.?

HEALTH-KIDS Project, ChicagoHEALTH-KIDS Project

A passion of Dr. Wang’s is to apply new scientific knowledge to serve underserved populations. A recent application is his NIH-funded school-based childhood obesity intervention study in Chicago—the HEALTH-KIDS Study (“Healthy Eating and Active Lifestyles from school To Home for KIDS”). It showed that a comprehensive intervention program targeting low-SES African-American students in Chicago Public Schools reduced the prevalence of obesity compared to schools without the intervention. In Beijing, supported by a research grant from the Nestle Foundation, his team is developing an innovative healthy eating promotion program among middle school students. In addition, he is working with local collaborators from the Nanjing Center for Disease Control and Prevention to develop school-based obesity prevention programs in that city.

Local and International Leadership

Dr. Wang has served on a host of international and domestic expert committees and boards. Close to home, the governor appointed him to the Maryland State Advisory Board of Physical Fitness. On a national level, he was elected in July to be the chair-elect of the Nutrition Epidemiology Section of the American Society for Nutrition (ASN). On an international level, he chaired a symposium entitled, “Obesity and Related Economic Issues” in the 7th World Congress on Health Economics held in Beijing, China, in July of this year. Meanwhile, he has served on international committees such as a WHO Expert Committee to help develop a new international growth reference for children and adolescents, and the International Union of Nutritional Sciences (IUNS) Task-Force on Diet, Nutrition and Long-term Health.

The Future
As Dr. Wang’s research portfolio continues to expand, he has had more opportunities for collaboration with other faculty across the university and with researchers from other institutions in the US and overseas. His recent NIH research grants related to obesity and chronic disease helped create two new positions at the Center for Human Nutrition: one faculty and one post-doctoral position. They will help carry out several ongoing research projects related to health disparities and the associations between social, behavioral, and environmental factors and risks of chronic diseases.

--Brandon Howard, September 2009