What are some of the reasons for the growing American waistline?
What does weight loss surgery involve?
How do ethnicity, gender, and socioeconomic status relate to patterns of overweight and obesity?
Is it better to eat quickly or slowly?
What is calorie restriction?

What are some of the reasons for the growing American waistline?

For several decades, and especially since 1990, the prevalence of overweight and obesity has been increasing in the United States. Despite widespread media attention and public health campaigns, the trend shows little sign of abating. A 2006 study reported that during the 6-year period from 1999 to 2004, the prevalence of overweight in children and adolescents increased significantly, as did the prevalence of obesity in men. There was no increase in the prevalence of obesity in women, however, suggesting that body weight increases may be leveling off in at least one segment of the population.

          The basic facts of energy balance help explain the expanding American waistline. According to the USDA, average calorie intake among Americans increased by more than 500 calories per day between 1970 and 2003, and levels of physical activity have declined. What are some of the factors underlying this change?

• More meals eaten outside the home, especially fast-food meals. Studies of adults have found that the more people eat out, the more calories they consume and the more body fat they have. The average American consumes 40%-50% of meals and snacks away from home. One-third of American children eat fast food on any given day, and children who eat fast food consume almost 200 more calories per day than those who don't.
• Increased portion sizes. The average fast-food burger, which weight about 1 ounce in 1957, now weighs up to 6 ounces. The typical serving of soda was 8 fluid ounces in 1957; now it is 32-64 ounces. The average movie theater serving of popcorn was 3 cups in 1957; today, it is 16 cups.
• Increased consumption of soda. Regular soft drinks are the leading source of calories in the American diet. Since 35 million U.S. public school students are plagued with obesity, soda distributors have agreed to stop most soda sales in public schools. The plan will go into effect in most schools by 2009 and in the rest by 2010.
• Lack of sleep. Most adult Americans get less than the recommended 7-8 hours of sleep per night, and evidence is mounting that insufficient sleep contributes to weight gain. Scientists believe this is because sleeplessness leads to an imbalance between two hormones involved in regulating the urge to eat. To combat this problem, experts suggest that people simply get more sleep.
• More time spend in sedentary activities. Americans now spend far more time watching television and movies, sitting in cars, playing video games, and in other sedentary activities than they do in activities that require more energy.

What does weight loss surgery involve?

Gastric bypass surgery modifies the gastrointestinal tract by changing either the size of the stomach or how the intestine drains, thereby reducing food intake. The two most common surgeries are the Roux-en-Y gastric bypass and the vertical banded gastroplasty (VBG/Lap-Band). In the Roux-en-Y gastric bypass procedure, the stomach is separated into two pouches, one large and one small. A "Y" segment of the small intestine is attached to the smaller pouch. The small stomach pouch restricts food intake, and the bypass of the lower stomach and part of the small intestine results in the absorption of fewer calories (and nutrients). Side effects include fat intolerance, nutritional deficiencies, and dumping syndrome, which involves gastrointestinal distress.

          In vertical banded gastroplasty (VBG), a small gastric pouch is created in the upper part of the stomach by applying a double row of staples that essentially elongates the esophagus. This small pouch empties into the remaining stomach through an outlet that is restricted with a band. The procedure controls the gastric emptying of food and the volume of foods eaten. Common complications associated with this kind of surgery are nausea, vomiting, band slippage, gastroesophageal reflux, and stenosis (constriction of the outlet). When compared with Roux-en-Y gastric bypass, VBG has a lower initial weight loss and a greater weight regain.

          In a variation of VGB, called Lap-Band, an adjustable band is placed around the stomach. The band is implanted laparoscopically, via a tube inserted through a small incision in the abdomen. the band ties off a portion of the stomach, creating a small pouch similar to that created in VGB surgery. The band is filled with saline and can be tightened or loosened by adding or removing saline through a small tube that exits through the patient's abdomen. The Lap-Band procedure has about the same success rate as VGB and is generally considered to be safe.

          Weight loss from surgery generally ranges between 40% and 70% of total body weight over the course of a year. For both of these procedures, the key to success is to have adequate follow-up and to stay motivated so that lifestyle behaviors and eating patterns are changed permanently.

How do ethnicity, gender, and socioeconomic status relate to patterns of overweight and obesity?

Among all population groups in the United States, the prevalence of overweight and obesity is growing. However, rates and trends vary by ethnic group and by other population characteristics:

• Certain groups, including African Americans, Latinos, and American Indians and Alaska Natives, have higher-than-average rates of obesity. Asian Americans have a low rate of obesity.
• There is considerable variation within populations grouped into general ethnic categories. For example, among Asian Americans, Vietnamese Americans, and Chinese Americans have very low rates of obesity and Asian Indians have much higher rates of obesity.
• Within all groups, women have higher rates of overweight and obesity than men.
• Low socioeconomic status is associated with higher rates of overweight and obesity. Researchers theorize that people living in poor communities are more greatly affected by a "toxic" food and exercise environment—meaning there are fewer opportunities to purchase healthy foods and engage in regular physical activity. In addition, many foods low in price are high in calorie density (fast food, for example).
• Higher or increasing socioeconomic status is associated with lower rates of obesity among some groups and constant or increased rates of obesity among other groups. Groups that are transitioning from poverty, food scarcity, and jobs that require significant energy expenditure may not have good family or community models of reducing energy intake and increasing leisure-time physical activity.
• Acculturation boosts body weight. The longer a foreign-born person lives in the United States, the more likely she or he is to become obese. BMI among immigrants begins to climb after about 10 years of U.S. residence, and after 15 years, it approaches the national average.
• Cultural factors that influence dietary and exercise behaviors appear to play a role in the development of obesity. There are also cultural differences in acceptance of larger body size and in body image perception. For example, one study found that African Americans were more likely to think they were thinner than they actually were and whites were more likely to think they were fatter than they really were.
• Some studies have found that African Americans, on average, have lower resting metabolic rates (RMR) than whites; in addition, weight loss may cause greater declines in RMR among African Americans. Further research is needed to determine the influence RMR differences may have on rates of obesity and successful weight loss among African Americans.
• The health consequences of obesity affect ethnic populations in different ways. At a given level of BMI, Latinos are significantly more likely to have type 2 diabetes. Obesity in African Americans is associated with increased risk of developing hypertension at a younger age and in a more severe form.
• For Asian Americans or person of Asian descent, waist circumference is a better indicator of relative disease risk than BMI, and disease risk goes up at a lower level of BMI than for individuals of other groups. For Asian populations, WHO guidelines have lower BMI cutoffs for defining overweight and obesity (BMI > 23).

Sources: Centers for Disease Control and Prevention. 2006. Racial and Ethnic Approaches to Community Health (REACH 2010): Addressing Disparities in Health (http://www.cdc.gov/nccdphp/publications/aag/reach.htm; retrieved July 23, 2007); Chou, J., and H.S. Juon. 2006. Assessing overweight and obesity risk among Korean Americans in California using World Health Organization body mass index criteria for Asians. Preventing Chronic Disease 3 (3): A79; Kumanyika, S., and S. Grier. 2006. Targeting interventions for ethnic minority and low-income populations. The Future of Children 16 (1): 187-207; Whitaker, R.C., and S.M. Orzol. 2006. Obesity among US urban preschool children: Relationships to race, ethnicity, and socioeconomic status. Archives of Pediatric and Adolescent Medicine 160 (6): 578-584; Goel, M.S., et al. 2004. Obesity among U.S. immigrant subgroups by duration of residence. Journal of the American Medical Association 292 (23): 2860-2867; Centers for Disease Control and Prevention. 2004. Prevalence of diabetes among Hispanics. Morbidity and Mortality Weekly Report 53 (40): 941-944.

Is it better to eat quickly or slowly?

When your stomach is empty, it sends signals to the brain that create the sensation of hunger (different people experience this sensation in different ways). As the stomach fills with food, it sends different signals to the brain to switch off the hunger sensation. However, it can take several minutes for your body to recognize that you have been eating and send this "off" signal to your brain. For this reason, experts say it is better to eat meals slowly—to give your body a chance to start feeling full and shut off the hunger mechanism. If you eat too quickly, you can consume more food in the same amount of time than if you ate slowly.

What is calorie restriction?

In a calorie restriction (CR) diet, a person consumes very few—in some cases, fewer than 1000—calories per day. CR proponents claim that such diets are a good way to lose and control weight, and that very-low-calorie diets can extend a person's lifespan and reduce the incidence of chronic diseases.

          There are several variations on CR diets, but most emphasize foods that are low in calories and high in nutrients. The stated goal of most CR programs is to ensure optimal nutrition (that is, getting adequate protein, carbohydrates, and essential nutrients) while ingesting the fewest possible calories. CR practitioners typically eat little or no meat, preferring to get their protein from vegetable sources.

          Although a few studies have shown that controlled CR diets can be beneficial in some organisms (such as certain rodents and insects), calorie restriction has not been well studied in humans and the alleged benefits of CR are widely disputed. Many scientists and nutrition experts dismiss CR as a sham, and even CR proponents acknowledge that very-low-calorie diets pose risks.