Fighting fat: America's new health war. .As a nation, almost two-thirds of us-an estimated 97.1 million adults and 6.7 million children and teens-are overweight, says the Centers for Disease Control and prevention Centers for Disease Control and Prevention (CDC), agency of the U.S. Public Health Service since 1973, with headquarters in Atlanta; it was established in 1946 as the Communicable Disease Center. . That's more than triple the number just 20 years ago. Why are Americans packing on the pounds? The obvious response: We eat too much. But scientists and health experts think that answer is deceptively simple--and the real question is why we overeat o·ver·eat v. To eat to excess, especially habitually. . Healthy bodies come in all shapes and sizes. But obesity, or extreme excess weight, is linked to around 300,000 U.S. deaths each year as a leading risk factor for killers like heart disease and diabetes, a blood-sugar disorder that can lead to blindness, nerve damage, and organ failure. [ILLUSTRATION OMITTED] How to deal with what the U.S. Surgeon General The U.S. Surgeon General is charged with the protection and advancement of health in the United States. Since the 1960s the surgeon general has become a highly visible federal public health official, speaking out against known health risks such as tobacco use, and promoting disease calls "the most pressing new health challenge we face today"? Researchers are probing the dizzyingly complex science behind how and why we gain weight. Both genetic (inherited) and environmental factors, like too much food and too little exercise, are under scrutiny-clearly a combination of factors fuels the American weight crisis. Read on to learn how scientists are fighting fat. [GRAPHIC OMITTED] Last year alone the nation shelled out $33 billion on weight loss products from low-calorie foods to diet pills--yet waistlines still expanded. Why? "The truth is, we don't really know," admits obesity researcher Dr. David Cummings at the University of Washington School of Medicine The University of Washington School of Medicine (UWSOM) is a public medical school located in Seattle, Washington. It is a graduate school affiliated with the University of Washington, and is the only medical school in the states of Washington, Wyoming, Alaska, and Idaho. . "But we do have an increasingly better understanding of the body mechanisms that control weight." According to Cummings, the shape of our bodies, how much we weigh, even how much we're able to eat, may be 50 to 80 percent determined by genes, units of hereditary information stored in our cells. The CDC See Control Data, century date change and Back Orifice. CDC - Control Data Corporation and National Institutes of Health agree that genes--which control hundreds of weight-regulating compounds in the body, like hormones and brain chemicals--may cause some of us to store more fat, burn fewer calories, and even crave more food. In other words Adv. 1. in other words - otherwise stated; "in other words, we are broke" put differently , there's a lot more to fatness than lack of willpower: "We need to remember that for obese people being overweight is not necessarily their fault," says Cummings. The evidence? Geneticists This is a list of people who have made notable contributions to genetics. The growth and development of genetics represents the work of many people. This list of geneticists is therefore by no means complete. Contributors of great distinction to genetics are not yet on the list. point to studies on identical twins identical twins pl.n. Twins derived from the same fertilized ovum that at an early stage of development becomes separated into independently growing cell aggregations, giving rise to two individuals of the same sex, identical genetic makeup, and , siblings born from a single fertilized fer·til·ize v. fer·til·ized, fer·til·iz·ing, fer·til·iz·es v.tr. 1. To cause the fertilization of (an ovum, for example). 2. egg who share a duplicate set of genes. University of Pennsylvania (body, education) University of Pennsylvania - The home of ENIAC and Machiavelli. http://upenn.edu/. Address: Philadelphia, PA, USA. scientists compared the body shapes and weights of identical and fraternal twins fraternal twins pl.n. Twins that derive from separately fertilized ova and that have different genetic makeup. They may be of the same or opposite sex. , siblings born from separate eggs with similar but not identical genes. The surprising study results: As adults, the identical twins had mirror-image body shapes and weights, even when raised apart. But fraternal twins had body shapes and weights as varied as unrelated individuals, even when growing up in the same home. How the genes interact in different people--and how much they're influenced by environmental factors, like food and eating habits--is still a mystery. But Cummings and his team are making strides: They recently discovered that a gene called ghrelin (GREY-lynn) plays a starring role in appetite control. In most healthy people, the ghrelin gene programs stomach cells to produce a powerful hunger-stimulating hormone, a chemical messenger that signals the brain to control body functions. Secreted into the bloodstream, the hormone travels to the brain and activates feeding centers--like the hypothalamus hypothalamus (hī'pəthăl`əməs), an important supervisory center in the brain, rich in ganglia, nerve fibers, and synaptic connections. It is composed of several sections called nuclei, each of which controls a specific function. , a forebrain forebrain: see brain. area that regulates food intake (see diagram, p. 18) among other body functions. The ghrelin hormone rises sharply before meals and plummets afterwards: In theory, the more you produce, the hungrier you feel. Cummings found that dieters who slash calories (see chart, right) have elevated pre-meal ghrelin levels--a condition that may trigger 'overeating. The body literally fights to stay fat, Cummings speculates. The question is, why? One possible explanation: "For millions of years the human species probably endured common periodic famine," Cummings says. A person whose body slowed down the rate at which it converted food into energy (metabolism) may have been able to fend off starvation. "Today, that's what happens to people who diet--their metabolisms drag," explains Cummings. "It's the body's old attempt to store food for the long haul." He hopes to develop a drug that blocks the ghrelin hormone to help obese individuals shrink their appetites, shed pounds, and keep them off. THE LIFESTYLE LINK Genes once advantageous to cave dwellers may be wreaking havoc on modern waistlines. Yet even if genes determine a major portion of our body type and weight, we still have considerable control over our "fat." "The current obesity epidemic doesn't completely reflect genetic factors--but big changes in the way we live our lives," says Dr. William H. Dietz at the CDC. For the first time in history, we have unlimited access to tasty foods dense with calories (energy units in food) and dietary/'at (energy-rich complex molecules). Our biggest challenge, says Dr. Kelly Brown at the Yale Center for Eating and Weight Disorders: controlling the urge to consume colossal food portions. A single serving of French fries in the 1960s contained 200 calories; today's super-size serving packs about 610 calories (see bar graph, left). At the same time, physical activity is tanking: 26 percent of kids ages 8 to 16 watch four or more hours of TV a day, while participation in gym class has dropped from 46 percent in 1991 to just 29 percent in 1999, according to the U.S. Department of Health and Human Services Noun 1. Department of Health and Human Services - the United States federal department that administers all federal programs dealing with health and welfare; created in 1979 Health and Human Services, HHS . "Never has there been a greater need to stress the importance of physical fitness," says HHS HHS Department of Health and Human Services. Secretary Tommy G. Thompson. Many studies show physically fit people are less likely to develop a host of diseases from diabetes to depression--regardless of body type. "We're far too hung up on weight," says obesity specialist Dr. C. Wayne Callaway at George Washington University George Washington University, at Washington, D.C.; coeducational; chartered 1821 as Columbian College (one of the first nonsectarian colleges), opened 1822, became a university in 1873, renamed 1904. . "I'd much rather see a heavy person who's physically active than a skinny person who's out of shape." Still, the U.S. Surgeon General urges Americans to shed extra pounds. "Most people can control up to 10 percent of their body weight," Cummings says. "Losing 30 pounds won't make a very heavy person look svelte, but it promotes incredibly positive health benefits." Why some people pack weight on more easily than others remains a puzzle, but in terms of obesity research, there's light at the end of the tunnel. "In the next decade we'll be able to manage weight problems with medications much as we now manage other illnesses," says Cummings. Doctors use the Body Mass Index (BMI BMI body mass index. BMI abbr. body mass index Body mass index (BMI) A measurement that has replaced weight as the preferred determinant of obesity. ) to help determine if a person is overweight. To calculate BMI, divide your weight (in pounds) by your height (in inches squared). Then multiply the results by 704.5. The National Institutes of Health generally defines overweight as a BMI of 25 to 29.9 and obesity as a BMI of 30 or greater. For more on BMI, see the Teacher's Edition. THE ENDOCRINE SYSTEM endocrine system (ĕn`dəkrĭn), body control system composed of a group of glands that maintain a stable internal environment by producing chemical regulatory substances called hormones. : HOW IT REGULATES WEIGHT CONTROL A complex network of glands (cell clusters) called the endocrine system works 24 hours a day to regulate body weight, it coordinates the release of hundreds of hormones, or chemical messengers, into your bloodstream. Hormones help control when and how often you feel hungry, how much you eat--even how quickly food is burned as energy. They also regulate sleep, breathing, growth, and emotions. HORMONES AND OBESITY Two hormones, leptin Leptin A protein hormone that affects feeding behavior and hunger in humans. At present it is thought that obesity in humans may result in part from insensitivity to leptin. and ghrelin, play an important role in obesity. Leptin Leptin is secreted into the bloodstream by fat cells found in the stomach. Leptin signals the brain's hypothalamus to secrete secrete /se·crete/ (se-kret´) to elaborate and release a secretion. se·crete v. To generate and separate a substance from cells or bodily fluids. hormones that suppress hunger. Ghrelin Ghrelin is secreted into the bloodstream by stomach glands. It signals the hypothalamus to secrete hunger-stimulating hormones. When people diet, ghrelin levels rise and leptin levels fall. Appetite increases, making it harder to lose weight. WEIGHT PATROL: KEY PLAYERS OF THE ENDOCRINE SYSTEM Brain Controls at least 40 neurotransmitters (brain chemicals) that regulate eating. Food releases the "pleasure-causing" chemicals dopamine dopamine (dōp`əmēn), one of the intermediate substances in the biosynthesis of epinephrine and norepinephrine. See catecholamine. dopamine One of the catecholamines, widely distributed in the central nervous system. and serotonin in the brain. Pituitary Gland pituitary gland, small oval endocrine gland that lies at the base of the brain. It is sometimes called the master gland of the body because all the other endocrine glands depend on its secretions for stimulation (see endocrine system). This pea-size "master gland mas·ter gland n. See pituitary gland. " secretes hormones that control most of the other endocrine glands endocrine glands (enˑ·dō·krin glandz′), n.pl ductless glands of the endocrine system that secrete hormones directly into the bloodstream. . Hypothalamus A brain region that fields and interprets eating cues from glands scattered throughout the body. Thyroid Secretes thyroxine, a hormone that speeds up the rate at which your body cells burn energy (metabolism). [ILLUSTRATION OMITTED] TOO MUCH OF A TASTY THING? AMERICANS spend 30 percent of their food dollars on fast food, says the U.S. Department of Agriculture. Food-on-the-go is often rich in fat and calories. [ILLUSTRATION OMITTED] THE BIOLOGY OF HUNGER SLIM GENES The leptin gene is thought to produce a hormone that curbs appetite in both humans and mice. The mouse on the left is more than three times its normal weight, because it was born with a faulty leptin gene. [ILLUSTRATION OMITTED] COULD THE STOMACH hormone ghrelin trigger our desire to eat? Scientists found that ghrelin levels rise sharply before meals, especially in dieters, but remain low after a drastic weight-loss surgery that reroutes food past the stomach to the intestines. Singer Carnie Wilson has kept off 15D lbs. since her gastric bypass surgery Gastric bypass procedures (GBP) are any of a group of similar operations used to treat morbid obesity—the severe accumulation of excess weight as fatty tissue—and the health problems (comorbidities) it causes. in 1999. [GRAPHIC OMITTED] SUPER-SIZE IT? AN ESTIMATED 13 percent of U.S. teens ere overweight. That's more then double the percentage in 197D, according to the CDC. One possible culprit: giant portion sizes. This bar graph compares portion sizes and calories of three common junk food junk food n. Any of various prepackaged snack foods high in calories but low in nutritional value. junk food items from 1955 and 2000. By whet percentage is a 20 oz soda larger than a 6.5 oz soda?
CALORIES/PORTION SIZE
FRIES
1995 2.3 oz 210 calories
2000 6.9 oz 610 calories
SODA
1995 6.5 oz 80 calories
2000 20 oz bottle 250 calories
CANDY BAR
1995 1.1 oz 150 calories
2000 3.7 oz 510 calories
Note: Table made from bar graph.
Did You Know? * What you eat even as a newborn may hardwire your body to store more fat cells as an adult, according to University of Buffalo researchers. Scientists fed newborn rats milk formula 49 percent higher in carbohydrates than the milk rats normally suckle suck·le v. suck·led, suck·ling, suck·les v.tr. 1. a. To cause or allow to take milk at the breast or udder; nurse. b. To take milk at the breast or udder of. 2. . Within the first 24 hours of feeding, the pups had abnormally high levels of insulin, a hormone that triggers cells to absorb sugar. (Sugar in the blood not used for energy is stored in the body as fat.) Two months later the rats began gaining weight, and became obese in adulthood--even in the absence of a carbo-rich diet. * According to the U.S. Surgeon General, some overweight kids may need only focus on maintaining their current weight while growing normally in height. Cross-Curricular Connection Social Studies: Study the history of fast food and how it changed America's eating habits. Be sure to compare restaurant menus from the early years to the offerings today. How are they different in selections and serving sizes? Critical Thinking: How have today's media outlets skewed skewed curve of a usually unimodal distribution with one tail drawn out more than the other and the median will lie above or below the mean. skewed Epidemiology adjective Referring to an asymmetrical distribution of a population or of data the perception of healthy body shapes? Resources "Fat for Life?" by Sharon Begley, Newsweek, July 3, 2000 The Surgeon General's Call To Action To Prevent and Decrease Overweight and Obesity: www.surgeongeneral.gov/topics/obesity/calltoaction/fact_adolescents.htm CHECK FOR UNDERSTANDING Directions: Answer the following in complete sentences. 1. What do doctors use to help determine if a person is overweight? 2. What body system regulates weight control? 3. In a comparison of food portion sizes between 1955 and 2000, what is the most significant difference? 4. What factor may determine 50 to 80 percent of our body shape, size, and how much we're able to eat? 5. According to numerous studies, what health risks are less prevalent in physically fit people? ANSWERS 1. Doctors use the Body-Mass Index to determine if a person is overweight. 2. The endocrine system regulates weight control. 3. The food portion sizes in 2000 are significantly larger than the portion sizes in 1955. 4. Our shape, size, and how much we're able to eat may be 50 to 80 percent determined by genes. 5. Studies show that physically fit people are less likely to develop a host of diseases from diabetes to depression. |
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