GLOBAL HEALTH | Addressing the world’s health challenges
18 July 2008
Obesity Becoming Worldwide Health Threat
Related health problems causing deaths in developed and developing nations
Washington -- One of the world’s fastest growing health threats is not a virus or a bacterium. Even though it is not contagious, it is spreading rapidly from its well-established base in the developed world into developing nations.
Over the past 30 years, obesity rates have increased dramatically worldwide and the well-documented health problems associated with obesity can be deadly: diabetes, heart disease and some forms of cancer. Once considered an issue only in developed countries, excess weight now is becoming a health problem in low- and middle-income countries as well.
According to a 1999-2000 national health and nutrition survey by the Centers for Disease Control and Prevention (CDC), 64 percent of U.S. adults are overweight or obese, a 36 percent increase over figures reported in a 1976-1980 survey. And this growing epidemic is expensive: CDC reports that in 2000 the United States spent an estimated $117 billion on obesity-related health issues.
According to 2005 projections by the World Health Organization (WHO), there are 1.6 billion overweight and 400 million obese adults worldwide. WHO predicts that by 2015 these numbers will increase to 2.3 billion overweight and 700 million obese adults. Children are not immune from excess weight either; WHO estimates there are 5 million overweight children worldwide.
THE PROBLEM
Obesity is defined as excessive adipose tissue (fat) that impairs health. The body mass index (BMI), calculated with an equation that incorporates height and weight, is a simple metric for assessing obesity. Other measures of obesity, such as waist circumference, can be used as an alternative measurement or supplement to BMI. Some argue that waist circumference is a superior risk-assessment tool because the abdominal area is considered the most dangerous location for adipose tissue to accumulate.
After a prolonged period during which more calories are consumed than are expended through exercise, obesity results. Obesity seems influenced by genes and environment.
Obesity often runs in families, which is one indicator that obesity has a genetic component, and researchers have identified a number of “obesity genes” they believe are linked in some way to an individual’s tendency to gain weight. As of 2005, some 11 genetic mutations were found to be associated with the risk of obesity. Understanding the physiological and genetic underpinnings of obesity can help researchers develop new, effective drug treatments.
Some researchers blame lifestyle changes for increased obesity rates over the past 20 years. Because calorie-dense foods are cheap and readily available, people eat more and adopt more sedentary lifestyles.
Certain hormonal disorders, like hyperthyroidism, also can lead to obesity. In addition, some studies suggest lack of sleep might contribute to obesity.
To combat obesity, doctors generally recommend lifestyle changes. A diet rich in vegetables, whole grains and low-fat animal products can help avoid excess body fat by decreasing calories consumed, and increased physical activity can boost calories burned.
RESEARCH EFFORTS
The CDC is collaborating with WHO on the Global Strategy on Diet, Physical Activity and Health. The program has four main objectives: reducing risk factors for chronic disease, increasing awareness and understanding of obesity, creating global action plans and promoting research. The program was initiated in May 2004 and since then, 38 countries have created policies for its local implementation.
In 2007 in the United States, the CDC’s Nutrition and Physical Activity Program to Prevent Obesity and Other Chronic Diseases funded obesity prevention and control activities in 28 states. This program aims to decrease obesity rates by promoting physical activity, consumption of more fruits and vegetables, an increase in breastfeeding and its duration, reduced consumption of energy-dense food and sugar-sweetened beverages, and less television viewing.
The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) recently opened a Metabolic Clinical Research Unit (MCRU) as part of the National Institutes of Health strategic plan for obesity research. The MCRU is, according to its Web site, “designed to foster a collaborative research approach, bringing together experts from the fields of metabolism, endocrinology, nutrition, cardiovascular biology, gastroenterology, hepatology, genetics, and the behavioral sciences.”
The director of the Metablic Research Core at NIDDK, Kong Chen, is studying differences in energy expenditure between lean and obese individuals using whole-room indirect calorimeters, devices that measure energy expenditure using temperature readings.
“Personally, we are interested in understanding how some individuals respond differently to diet, exercise, weight loss or weight gain,” Chen said. “We believe that some people may be more adaptive than others by altering their energy metabolism [how many calories are burned and from what fuel sources] under such stimuli. Typically, these changes are small but may be very important because they impact our body weight over time.”
There are several peer-reviewed scientific journals on the subject of obesity and a scientific association called the Obesity Society that publishes the journal Obesity. Society member Dr. Steven Smith, a professor at the Pennington Biomedical Research Center, deals with patient care and research.
In his studies, Smith found people whose muscle cells easily burn fat are leaner than people whose cells favor glucose.
“We are very interested in how you might be able to reprogram cells to favor a different fuel through dietary modifications,” he said.
