O 468 oats (Avena sativa) A common cereal GRAIN grown in temperate regions, particularly in North America and northern Europe. There are six species, including common oats and cultivated red oats, that are grown in the Americas. Oats are clas- sified as winter and spring varieties, according to their planting time. Only about 5 percent of the U.S. crop is used as a food crop; most ends up as livestock feed. An inedible, loose, pithy hull sur- rounds the kernel, or groat, and must be removed for human consumption. Pure oats and pure oat BRAN are the least processed form of oats. Oat flakes, prepared by steaming and flaking whole kernels, are the basis for porridge. Oatmeal is prepared by cutting ker- nels to small granules with a mealy texture. Con- sumption of old-fashioned oatmeal as a BREAKFAST CEREAL has declined with the increased popularity of ready-cooked oatmeal cereals. Rolled oats, pre- pared by crushing oats with still rollers, are used in breakfast food, cookies, breads, and GRANOLA, which is a mixture of rolled oats, honey, nuts, raisins, or dates. Milling produces oat flour. Oat flour contains a natural ANTIOXIDANT that increases the stability of oat flour in storage. Oat Bran Oat bran is derived from an outer layer of oat ker- nels by milling. It is a good source of SILICON, a trace mineral needed for healthy joints, and a form of FIBER called beta-glucan. The fiber in oat bran is water soluble and differs from water-insoluble WHEAT bran, the kind usually found in bran- enriched breakfast cereals. Eating oat bran daily in muffins and a bowl of hot oatmeal—together with daily exercise and eating less animal FAT as found in red MEAT and BUTTER—can lower blood fat and CHOLESTEROL even in diabetics. Oat bran alone has a modest effect in lowering elevated levels of the less desirable LOW -DENSITY LIPOPROTEIN (LDL) cho- lesterol. Oat bran has been used as a fat substitute to reduce fat in beef and pork sausage products. A mixture of oatmeal and oat flour has been devel- oped by the USDA as a fat-substitute called Oatrim or “hydrolyzed oat flour.” Oatrim contains one calorie per gram, as compared with nine calories per gram of fat and four calories per gram of STARCH. This fat substitute is used in baked goods and processed meats, and other products are under development. Oatmeal Hot oatmeal is a traditional breakfast, and its emer- gence as an important source of fiber has caused a resurgence in popularity. Steel cut, rolled, or quick- cooking oats all contain the same amount of fiber. However, processed, cold oat breakfast cereals con- tain much less fiber (about 2 g per serving). Dry oatmeal contains about 14 percent protein, but cooked oatmeal is only about 2 percent protein. Nutrient content of regular cooked oatmeal or rolled oats, (1 cup fortified) is: 145 calories; pro- tein, 6 g; carbohydrate, 25.2 g; fiber, 9.23 g; fat, 2.3 g; iron, 1.6 mg; sodium, 285 mg; vitamin A, 453 retinol equivalents; thiamin, 0.53 mg; riboflavin, 0.29 mg; niacin, 5.9 mg. obesity An excessive accumulation of body fat for a given body size based on muscle and bone (frame size). In 1998 the federal government adopted new standards for determining whether a person is overweight or obese. Before then, people were considered overweight if their weight was at least 10 percent to 20 percent over optimal body weight. Obesity was defined as being more than 25 percent over the optimal body weight for men and 30 percent over the optimal body weight for women. Under the new standards, a person with a BODY MASS INDEX (BMI) of 25 or more is considered over- weight. The BMI is determined by dividing a per- son’s weight in kilograms by the square of his or her height in meters. A healthy BMI falls between 19 and 25. A person with a BMI of 30 or above is con- sidered obese. According to statistics compiled by the World Health Organization, obesity is increasing worldwide—an estimated 1.2 billion people in the world are overweight. Its rapid increase among Americans during the 1990s (12 percent in 1991 to 17.9 percent in 1998) prompted some health offi- cials to conclude that it had reached epidemic pro- portions. In 2001 27 percent of adults between the ages of 20 and 74 were obese. The rate of over- weight among children was 13 percent. Based on these figures, a former U.S. surgeon general, David Satcher, concluded that overweight and obesity may soon cause as much preventable disease and death as cigarette smoking. The condi- tions were already responsible for as many as 300,000 premature deaths each year, costing the nation an estimated $117 billion. The prevalence varies among groups. The average American adult gains a pound a year through middle age. Childhood obesity has increased dramatically since 1965 in the United States, reflecting an increased prevalence of obesity among children in Western countries. The rising rate of overweight and obesity among young people is of special con- cern because childhood and adolescence is often a time in life when people are the most active and therefore least likely to gain excessive weight. Also, unhealthy nutrition and lifestyle habits that lead to overweight and obesity developed during this time have a good chance of continuing into adulthood. The number of obese Americans has increased, despite a national preoccupation with dieting. The fear of being fat has become an American obses- sion. U.S. society places a premium on being slen- der and most women and some men have dieted at least once. Being obese or overweight often brings a profound social stigma affecting personal life, life insurance premiums, and employment opportuni- ties. Nevertheless, in the 1980s the renewed inter- est in healthy lifestyles in America apparently affected a limited number of people. Sedentary lifestyles continue to prevail. Types of Obesity Hyperblastic obesity is characterized by an exces- sive number of fat cells. Increased fat cell size is classified as hypertrophic obesity, and individuals with hyperblastic-hypertrophic obesity have increased numbers of enlarged fat cells in their adi- pose tissue. Hyperblastic obesity is usually associ- ated with childhood, while hypertrophic obesity develops later in life and is associated with diabetes and other aspects of metabolic imbalance. Obesity as a Health Hazard It has been noted that the death rate increases 2 percent for each pound over a person’s healthy weight. For persons who are 40 pounds over- weight, the death rate is estimated to be 80 percent higher during the next 25 years of their life. Lean men survive longer than overweight men in the United States. Obesity increases the risk of HEART DISEASE , diabetes, GOUT, ARTHRITIS, CANCER of the liver and esophagus, GALLSTONES, hernia, intestinal blockage, kidney disease, and TOXEMIA of preg- nancy. In the United States, obesity increases the risk of angina, high blood pressure ( HYPERTENSION), high blood fat, elevated ( LOW-DENSITY LIPOPROTEIN) LDL, and sudden death from heart disease. One clue to understanding the relationship between obesity and elevated blood fat is the observation that obese people have higher insulin levels, which seems to promote higher blood lipids. The location of fat accumulation makes a differ- ence in health risks. Male-patterned obesity, with fat deposited primarily in the abdomen and trunk, is called android obesity (the “spare tire” or “apple” profile). Android obesity in men or women is asso- ciated with an increased risk for CARDIOVASCULAR DISEASE , hypertension, elevated BLOOD SUGAR, and gallstones. The greater the proportion of abdominal fat, the greater the risk. Abdominal fat may be more readily converted to cholesterol than fat deposited elsewhere. Pear-shaped people, with fat accumulation around the hips, do not experience as much diabetes or high blood pressure or as many heart attacks as those whose fat is around the middle. obesity 469 Possible Mechanisms for Regulating Body Weight Complex mechanisms involving the NERVOUS SYS- TEM, the ENDOCRINE SYSTEM, and the DIGESTIVE SYS - TEM, and adipose tissue regulate eating, energy balance, and thus obesity. Regions of the brain, such as the HYPOTHALAMUS and the brain stem, help reg- ulate food intake, body weight, body size, and body fat content. The hypothalamus plays a critical role in eating and balancing energy requirements with intake. The lateral hypothalamus controls eating activity; the paraventricular nucleus regulates nutri- ent balance and the ventromedial hypothalamus regulates energy balance by regulating the sympa- thetic nervous system, which helps the body adapt to stress. The hypothalamus regulates the ENDOCRINE SYSTEM (hormone secreting system). It activates the PITUITARY GLAND, which signals the adrenal gland to release GLUCOCORTICOIDS . In turn, these STEROID hor- mones regulate the nervous system, appetite, and fat metabolism. Obesity is linked to altered function of the brain stem and hypothalamus and to changes in the autonomic nervous system, which regulates energy expenditure and regulates thermogenesis. At the molecular level, altered production of NEURO- TRANSMITTERS, chemicals required to transmit nerve impulses, brain peptides, and brain hormones, may alter critical control and feedback mechanisms that maintain body weight. Several hypotheses link food intake and energy balance to regulate body weight through an inter- play between the endocrine system and the ner- vous system. A hypothetical very general control system involves the following components: A pro- posed “controller” resides in the brain. Signals leav- ing the brain regulate heat production, physical activity, food intake, energy storage as fat, and metabolism for doing work and producing heat. These factors stimulate the release of hormones. Nutrients and hormones from various glands and fat cells are then carried back to brain centers that in turn generate signals that are interpreted by the hypothalamus to diminish eating. Stomach disten- sion triggers the nervous system to create a feeling of fullness. The action of GLUCOSE (blood sugar), fat, and protein in the intestines on receptors could also send signals back to the brain to diminish eat- ing behavior. In 2002 researchers reported that the recently discovered “hunger hormone” ghrelin might be a significant factor in determining why some people become obese and why most people find it hard to keep weight off once it is lost. A study of a small group of obese people revealed they had much higher blood levels of ghrelin, which is produced by stomach cells, after they lost weight through diet control and exercise. In contrast, people who lost weight after gastric bypass surgery, which reroutes the flow of food, had low levels of ghrelin. The extremely low levels of ghrelin in people who had undergone gastric bypass surgery might explain why these people were usually more suc- cessful in keeping weight off. Researchers cau- tioned that the results were preliminary and that ghrelin is probably only one of many tools the body uses to regulate body weight. Another hypothesis predicts a “set point” that tends to keep body weight at a constant level. According to the “set point” hypothesis for body weight, each person has a biologically determined body weight, believed to be inherited. In some obese individuals, the set point may be too high. When fat cells decrease in size (for example, after DIETING) they could indirectly signal the brain to increase food consumption. Thus, an obese person with large numbers of fat cells could crave food, leading to excessive eating after dieting. According to a related hypothesis, some obese people earlier in their lives, perhaps during early childhood, ate much more than their bodies needed during their formative years. According to this proposal, this event patterned the body for burning energy and storing fat. Once overweight, obesity in these indi- viduals could be sustained even when consuming an average amount of food. Insulin insensitivity (resistance to the action of insulin) correlates with obesity; increasing tissue sensitivity to insulin is hypothesized to lower the body’s set point. Recent discoveries shed light on the relationships among obesity, satiety, and non- insulin dependent diabetes. Fat cells normally secrete a protein called LEPTIN that induces satiety. Leptin signals the brain to reduce consumption of fatty foods and possibly to increase the basal metabolism of fat cells. Therefore, leptin helps reg- ulate body weight by limiting body fat accumula- 470 obesity tion. Mice with mutations on the gene coding for leptin become obese. Researchers now believe obese people often make more than enough leptin, but the brain does not respond effectively to shut down eating because its binding sites or cell signal- ing mechanisms are defective. A region of the brain likely to be affected by leptin is the HYPOTHALAMUS, which integrates many functions of the body. Specifically, the region known as ventromedial nucleus, which regulates satiety, may be involved. Leptin could shut off signals in the brain that direct feeding (hunger signals), including neuropeptides. One possibility is neuropeptide Y, which induces lab animals to eat more carbohydrate and fat. In the set point model, leptin could act like a ther- mometer: When the body gets too thin, less leptin is made, more food is eaten, and less energy is con- sumed. When the body gets too fat, more leptin is made, less food is consumed, and more energy is burned. A variety of mutations in other genes link obe- sity and diabetes. As an example, mutations in a protein called beta 3 -adrenergic receptor, an attach- ment site which binds a NEUROTRANSMITTER (norep- inephrine), increase the risk of middle-age weight gain and diabetes. Under normal conditions norep- inephrine produced by the sympathetic nervous system stimulates fat cells to burn stored fats. The implication is that with a faulty neurotransmitter attachment site in fat tissue, the body burns less fat efficiently and calories accumulate. As an alterna- tive to the set point hypothesis, the “settling point” theory proposes that body weight is not fixed, but that it is maintained according to feedback loops that are determined by an interplay between genes and environment. Systems controlling hunger and satiety respond rapidly to dietary protein and car- bohydrate, but the feedback from a fatty meal may be too slow to prevent overconsumption. Thus, increased dietary fat could alter the body’s equilib- rium and shift body fat upward. The number of fat cells in the body is a determining factor. Fat cells are added during childhood and it could very well be that how much fatty food is consumed and how many calories are burned before adulthood has a major impact for the risk of obesity. Human obesity is a complex phenomenon with many causes. Inheritance as well as diet and med- ical history can contribute to excessive weight gain and many questions about the detailed interrela- tionships remain unanswered. Apparently, many genes interact to control weight, it is therefore unlikely that any single pharmacologic agent related to a gene product will substitute for chang- ing the diet and exercising regularly to maintain desired weight. In any event, very extensive clini- cal experience suggests that diets—that improve insulin sensitivity and glucose tolerance by empha- sizing VEGETABLES and LEGUMES and minimizing sugary or high fat foods—together with regular physical exercise can support long-term weight loss and reduce the risk of cardiovascular disease. Causes of Obesity Many adults achieve an energy balance in which caloric intake matches energy expenditure. Body fat does not change very much under these condi- tions. Excessive body fat could be related to eating more calories or to small energy expenditure, or both. Energy expenditure refers to the calories spent for body functions, physical activity, diges- tion, and food metabolism. Both heredity and the environment play a part in obesity and, therefore, there is no single approach to treatment. Overeat- ing, differences in metabolism, AGING, genetic pre- disposition, and excessive food consumption during early childhood have been implicated. Overeating Clearly the prolonged consump- tion of excessive calories, when energy intake exceeds energy expenditure, leads to obesity. Energy expenditure refers to the calories spent for body functions, physical activity, digestion, and food metabolism. Body fat can be reduced only when energy expenditure exceeds caloric intake. The body adapts to excessive food consumption— whether excessive PROTEIN, CARBOHYDRATE, fat, or ALCOHOL—by storing the surplus calories as body fat. Many reports have suggested that obese people eat the same, or sometimes less than nonobese people. Using new research methods based on ingesting double-labeled water, that is, water con- taining a “heavy” form of oxygen (O 18 ) and “heavy” hydrogen (deuterium), investigators have demonstrated that, on the average, obese people generally eat more, but they habitually underre- port their food consumption. obesity 471 Differences in Energy Expenditure Although obese people are generally less active than non- obese people, they tend to use the same amounts of energy because they weigh more. Sedentary lifestyles contribute to obesity. About 70 percent of adult Americans fail to exercise 20 minutes or more three times a week as recommended. Most people will lose weight if such an exercise program is coupled with consuming no more than 1,500 calories daily. Individuals who exercise regularly, or who exercise before and after a high- calorie meal, lose more energy as heat after eating than those who do not exercise. Differences in Metabolism This picture is unclear. Very rarely do glandular imbalances lead to obesity. Cushing’s syndrome, excessive produc- tion of glucocorticoids, a form of adrenal hormone, is an example of hormone imbalance that can pro- mote obesity. Obese people do not have unusually slow metabolisms. When resting metabolic rates are compared based upon the muscle/bone mass, there is not a significant difference between meta- bolic rates of nonobese and obese individuals. For- merly obese individuals preferentially store fat rather than burn it, and studies suggest that over- weight and obese people tend to eat more fat and less carbohydrate. In general, the body consumes calories more slowly after weight is lost, and it burns calories more rapidly when weight is gained, for fat as well as for thin people. One hypothesis contends that people adjust their metabolism to maintain a “set point” weight. Thus someone who has lost significant amounts of fat (10 percent of their body weight) will burn fewer calories when exercising than someone who has maintained his or her weight without a weight-loss program. Apparently, the body adjusts its metabolism by altering the efficiency of muscles in burning calo- ries. Recently, a type of prostaglandin has been shown to act as a hormone to trigger the produc- tion of fat cells from immature cells. Aging In the United States, both men and women tend to become fatter with increasing age. This could be due to a decreased metabolic rate (a lower BASAL METABOLIC RATE) and a sedentary lifestyle coupled with an easy access to high-calorie food. Meal Frequency The frequency of meals and meal composition may be a factor in obesity. Eating fewer meals may increase fat deposition, while smaller, more frequent meals, with more food at breakfast and less at supper, may promote weight loss. TV Watching Excessive TV watching correlates with overeating. Reduced physical activity, lowered metabolic rates, as well as visual cues to eating high-fat snack foods and drinking alcoholic bever- ages, contribute to the increased prevalence of overweight. Dietary fat, which provides nine calo- ries per gram, is more fattening than either protein or carbohydrate, which provide four calories per gram. Fat calories in food differ from calories in carbohydrate: Fat in food is more easily converted to body fat than is carbohydrate. Inheritance One broad generalization can be made: Obesity persists over a life span. Fat children tend to become fat adults, suggesting a predisposi- tion to being overweight. Early adulthood is an important period for the development of lifelong patterns. The question remains, to what degree is obesity the product of genetics? Studies with twins suggest that between 50 percent and 70 percent of the variability in relative body weight represents genetic variability. Current research focuses on locating specific obesity genes. Genes influence both metabolism and behavior. Many genes regu- late hunger and satiety. A flurry of recent research has yielded impartial genetic discoveries: gene OB causes fat cells to produce a satiety protein called lepin. A gene then codes for the receptor of this hormone in the brain. Still another gene codes for a hormone-producing enzyme (carboxypeptidase E). A gene that codes for a neurotransmitter recep- tor (binding site; Beta 3 -adrenergic receptor) for norepinephrine is also implicated in maintaining weight. Mutations of these genes can increase the risk of obesity and diabetes in lab animals and pos- sibly in people. There will be more to add to this unfinished story as more discoveries are made. Successful Weight Loss A Willingness to Change Therapeutic ap- proaches to obesity and weight management have met with only modest success. Only 2 percent to 10 percent of Americans who diet to lose weight and participate in weight loss programs will keep the pounds off more than several years. Most of the lost fat is regained within a few months after the dieter 472 obesity discontinues the diet regimen. Dieting without a long-term commitment to changing daily habits is destined to fail. Attitude is perhaps the most prominent factor in changing behavior. Regarding overeating, under- standing underlying feelings for which overeating compensates seems essential for permanent weight loss. Eating can provide immediate gratification, but this seldom resolves deep-seated emotional issues. After short-term sensory satisfaction, emotional pain or longing often returns. For example, responding to feelings of low self-esteem by crash dieting does not solve the underlying issue, and too often the dieter returns to old eating habits. Coun- selors recommend beginning with an inventory of talents and qualities that fill your life with the most satisfaction and choosing activities and relationships that bring satisfaction and a sense of well-being. Slow Weight Loss Successful long-term weight control requires the slow loss of body fat without cyclic, on-again, off-again dieting ( YO-YO DIETING). Losing a pound a week helps maintain muscle ( LEAN BODY MASS) while preferentially losing fat. Exercise Exercising for life helps keep the body engine “revved up,” so that more calories are burned by muscle and less insulin is required to dispose of elevated blood sugar following meals. Improved Diet A high-fat, high-calorie, low- fiber diet is thought to be the major dietary factor in obesity in the United States. Therefore the rec- ommended diet might be low in fat, high in fiber and complex carbohydrates (60 percent to 70 per- cent of calories), with adequate protein (10 percent to 15 percent of calories). Emphasis on natural, whole foods simplifies this task of avoiding the per- vasive high-calorie foods that fill the American food landscape. Another approach to obesity and overweight focuses on helping people through advocacy and social support with the premise that being overweight can be part of an enjoyable, ful- filling life: The Association for the Health Enhance- ment of Large People and the National Association to Advance Fat Acceptance are two such groups. Weight Loss Drugs Like diets, anti-obesity drugs tend to be effective only as long as the patient follows the prescription. When drugs are withdrawn, weight lost usually returns unless permanent behavior changes have been made. Amphetamines have adverse side effects: They have the potential for addiction and tolerance (more drug is required to get the same effect with chronic use). Another class of drug pro- motes nutrient malabsorption so that patients tak- ing these drugs do not absorb calories efficiently. Two appetite suppressants, fenfluramine and dexfenfluramine, were taken off the market by the U.S. FDA in 1997 when it was discovered that thou- sands of patients who took these drugs developed potentially deadly primary pulmonary hyperten- sion and heart valve abnormalities. Dexfenflu- ramine was shown to cause these injuries when taken alone, and fenfluramine was linked to valve problems in patients who combined it with the drug phentermine in a mixture popularly known as “fen-phen.” Both fenfluramine and dexfenflu- ramine helped patients lose weight by increasing serotonin levels in the blood stream, which pro- vided a sense of well-being and satiety. The prob- lem, researchers discovered after the drugs were removed from the market, was that the drugs destroyed the body’s ability to control the amount of serotonin circulating in the blood. Excessive amounts of serotonin can cause cell damage to car- diopulmonary structures. In late 2000 the FDA issued a public health advi- sory warning patients about phenylpropanolamine hydrochloride (PPA). This drug is widely used in both over-the-counter and prescription-only nasal decongestants and for weight control in some over- the-counter drug products. The warning was issued after medical researchers published a study show- ing that phenylpropanolamine increases the risk of hemorrhagic stroke (bleeding into the brain or into tissue surrounding the brain) in women. Men may also be at risk. Since then the FDA has taken steps to remove PPA from all drug products. No drug is both entirely safe and effective for weight loss, nor is it certain that taking current medications for many years is better than being fat. Drugs that sup- press appetite are not recommended for those who wish to lose only 5 to 10 pounds of fat. Childhood Obesity An estimated 13 percent of U.S. children six to 11 years old and 14 percent of adolescents 12 to 19 years old are overweight. The number of obese children and adolescents in the United States dou- obesity 473 bled between 1982 and 2002. Obesity is recognized as a U.S. epidemic affecting children. Low-income minority children face even higher rates of obesity. An overweight adolescent between age 10 and 14 who has at least one overweight or obese parent has a 79 percent likelihood of being overweight as an adult. Childhood obesity is linked to many of the fac- tors that cause adult obesity: Heredity As in adult obesity, genes play a role. Children born to obese mothers are more likely to be obese. If both parents are obese, the probability of their children becoming obese is very high. Overfeeding Some babies have more fat cells than usual. If they are also overfed, they are more likely to become obese children. In addition, over- feeding a child may lead to larger, not more, fat cells. This may make controlling weight more diffi- cult as an adult. (It should be pointed out that plump babies do not necessarily become obese adults.) Lower Metabolism Infants who become over- weight during their first year have a lower basal metabolic rate than usual. Their mechanism for reg- ulating body weight might be lower than average. Eating Too Much Fatty Food The more JUNK FOOD is consumed, the more likely the child will be obese. Bogalusa Heart Study is an ongoing popula- tion study to examine risk factors for cardiovascu- lar disease in children. Results from this study reveal that children who consume more than 30 percent of their calories from fat were more likely to eat less CALCIUM, IRON, MAGNESIUM, and vitamins like RIBOFLAVIN, NIACIN, THIAMIN, VITAMIN B 6 , VITA- MIN B 12 , and VITAMIN E. Too Much TV and Not Enough Exercise The odds of becoming obese increase with the number of hours of TV viewed each day. Children’s basal metabolic rate decreases, and they get less physical activity. Children who watch TV eat more of the high-calorie, highly processed food they see adver- tised, and parents fill the role of food “gate keepers.” Children eat what is available to them, whether it is candy, soft drinks, or fatty convenience foods, or fruit, low-fat foods, and sugar-free beverages. The home environment and parents present the model for a child’s eating habits. A child’s shift to a more healthful lifestyle needs to be nurtured by parents to become permanent. As with overweight adults, regular exercise is extremely important in children’s health and maintaining a desirable weight. However, overzealous dietary restrictions by parents can encourage self-imposed dieting and eating disorders, a prevalent problem among chil- dren and adolescents in the United States. As many as 80 percent of 10-year-old girls suffer from a fear of body fat; some already show signs of dieting, bingeing, overeating, and anorexia. The message they are receiving is that any accumulation of body fat is socially unacceptable. However, among white, middle-class, healthy girls in the United States, weight before and during puberty does not seem to be a predictor of weight gain at middle age. On the other hand, weight gained after puberty (during early adolescence) has correlated with weight gain as adults. For boys, prepuberty weight appears to be a good predictor of adult obesity. A physician should be consulted before talking to children about weight. Periodic increases in fat, especially among girls, are a normal occurrence. Weight maintenance, after the child has grown into his or her own weight, is preferable to dieting. Generally, children can be taught to prefer lower fat foods by exposure and availability. (See also MALNUTRITION; WEIGHT MANAGEMENT .) Asayama, Kohtaro et al. “Increased Serum Cholesterol Ester Transfer Protein in Obese Children,” Obesity Research 10 (2002): 439–446. Cummings, D. E. et al. “Plasma Ghrelin Levels After Diet- Induced Weight Loss or Gastric Bypass Surgery,” New England Journal of Medicine 346, no. 21 (May 23, 2002): 1,623–1,630. octacosanol A complex alcohol that is a normal constituent of wheat germ and wheat germ oil. Other sources include whole grain cereals, seeds and NUTS, and many plant oils and WAXES. Persis- tent claims that octacosanol supplementation has a positive effect on physical endurance and muscular strength have not been substantiated by research. The Federal Trade Commission concluded that wheat germ oil did not improve endurance or sta- mina. Octacosanol seems to improve reaction time. (See also ERGOGENIC SUPPLEMENTS.) oil See VEGETABLE OIL. 474 octacosanol oil palm (Elaeis guineensis) A palm that is a major source of edible oil. The oil palm yields more oil per acre than any other plant. It originated in West Africa, and plantations now exist in Malaysia, China, and Indonesia, as well as Tanzania, the Ivory Coast, Nigeria, and other regions. Palm oil is prepared from fibrous pulp of the fruit, and palm kernel oil is obtained from the seed or kernel, which contains about 50 percent oil. Palm kernel oil is used for margarine production and food man- ufacture. It is among the most SATURATED FATS , con- taining 86.7 percent saturated FATTY ACIDS , 1.6 percent polyunsaturated fatty acids, and 11.7 per- cent monounsaturated fatty acids. (See also COCONUT OIL; TROPICAL OILS.) okra (Hibiscus esculentus; Abelmoschus esculen- tus) A vegetable that bears seeds in edible pods whose ancestors may have been widely distributed from Africa to India. Okra now grows in regions with a moderate climate, including the southern states of the United States. Much of the U.S. okra crop is frozen or canned. Okra contains a mucilage that acts as a thickener in soups and stews. Because okra changes to an unappetizing color when cooked in utensils containing iron, copper, or brass, glass or stainless steel containers are used. Okra’s slippery mucilage is balanced by acidic foods like tomatoes and lemons and by vinegar. Okra, long considered part of Deep South cuisine, is also part of Indian, Caribbean, South American, and African recipes. Nutrient content of okra (8 pods, 85 g, cooked) is: 27 calories; protein, 1.6 g; carbohydrate, 6.1 g; fiber, 2.75 g; calcium, 54 g; iron, 0.38 mg; potas- sium, 274 mg; vitamin C, 14 mg; thiamin, 0.11 mg; riboflavin, 0.05 mg; niacin, 0.74 mg. oleic acid A nonessential FATTY ACID and a com- mon constituent of FATS and OILS found in foods and fat synthesized by the body. Oleic acid is dis- tinguished from the other common fatty acids, the energy-rich building blocks of fats and oils. It con- tains 18 carbon atoms and a single double bond, is deficient in hydrogen atoms, and thus is classified as a monounsaturated fatty acid. In contrast, satu- rated fatty acids are building blocks filled up with hydrogen atoms and polyunsaturated fatty acids possessing two or more double bonds and are more unsaturated than oleic acid. Oils rich in oleic acid are called monounsaturated oils. VEGETABLE OILS like olive oil, AVOCADO oil, and CANOLA OIL contain high amounts of oleic acid. Oleic acid-rich veg- etable oils seem to lower the less desirable forms of blood CHOLESTEROL, LOW-DENSITY LIPOPROTEIN (LDL) with high fat intake, and to increase more desirable forms of cholesterol, HIGH-DENSITY LIPOPROTEIN (HDL). Olive oil is more stable to oxidation than polyunsaturates such as safflower oil or corn oil. The recommendation is to decrease fat and oil con- sumption generally, and to use more monounsatu- rates in cooking, rather than saturates (butter, lard, shortening, coconut oil, or palm oil) or polyunsat- urates (such as CORN OIL, SAFFLOWER oil, and SOY- BEAN oil). Olestra (sucrose polyester, imitation fat [Olean]) A noncaloric fat substitute approved for use in snack foods such as crackers, potato chips, and other chips. Olestra tastes like LARD and VEGETABLE OILS ; it is neither digested nor absorbed by the body. By comparison, FAT and oils contain 126 calo- ries per tablespoon. Olestra resembles the structure of fat, except that it has a molecule of sucrose at its core to which are attached eight fatty acids, rather than three. Because it possesses a new substance, sucrose polyester had to be approved by the U.S. FDA . All products containing Olestra are labeled to notify the consumer that Olestra may cause abdominal cramping and loose stools and that it inhibits the uptake of certain nutrients. Vitamins A, D, E, and K have been added. The question of mal- absorption of CAROTENOIDS has not been addressed. In addition to these potential safety problems, animal studies suggest Olestra can cause liver dam- age, birth defects, and cancer. More complete stud- ies are needed to establish its safety. Regardless of their source, fat substitutes cannot replace the need to eat less high-fat food and to change eating habits. (See also WEIGHT MANAGEMENT.) olive (Olea europaea) The oil-rich fruit of a semitropical evergreen adapted to hot, dry cli- mates. Olives were probably first cultivated in the Eastern Mediterranean region as early as 6000 B.C. There are now more than 60 varieties. Mediterran- olive 475 ean countries remain major producers; together, Italy and Spain produce more than half of the world’s olives and 60 percent of the world’s olive oil production. Olives are also grown in Australia, China, Greece, Turkey, and France, as well as in the United States. Spanish colonists introduced olives to California in the 18th century; that state contin- ues to be a major domestic supplier. At maturity, ripened olives contain 15 percent to 35 percent oil, and OLIVE OIL is a major cooking oil. The oil content varies according to soil conditions, climate, and time of harvest. Olives must be processed for consumption. In the Spanish method, green (unripe) olives are first treated with alkali, then fermented, and canned or bottled. The alkali destroys a bitter constituent called oleuropein. In the American method, half- ripe, reddish fruit are cured in lye (strong alkali). Olives darken as pigments oxidize. They are rinsed and then placed in fermentation tanks containing BRINE. In the Greek method, fully mature olives are harvested and soaked in brine to remove the bitter components. Ripe, pitted olives (10.47 g) provide 50 calories; protein, 0.4 g; carbohydrate, 2.9 g; fiber, 1.4 g; fat, 4.5 g; calcium, 42 mg; iron, 1.5 mg; sodium, 410 mg; and traces of B vitamins. olive leaf extract The extracted juice of the leaf of the olive tree. This substance has been used for cen- turies as an herbal remedy for a variety of ailments, especially infection and fever. In the mid-1800s Dr. Daniel Hanbury reported that olive leaf extract was effective in reducing fever associated with an epi- demic of malaria on a Mediterranean island. In recent decades researchers have discovered that eleuropein, an ingredient in olive leaf extract, has antibacterial, antiviral, and anti-inflammatory properties and may help reduce the risk of CORO- NARY ARTERY DISEASE by lowering LOW-DENSITY LIPOPROTEIN (LDL) CHOLESTEROL. Laboratory studies conducted in the 1960s revealed than an active ingredient in eleuropein (elenolic acid) either killed or inhibited the growth of a number of path- ogenic organisms, including bacteria, yeasts, and viruses, but because the compound rapidly binds to proteins in the blood, rendering it ineffective, attempts to develop a marketable drug from the substance were abandoned. There is limited clinical evidence suggesting that olive leaf may help lower high blood pressure. However, reliable clinical studies on human beings that confirm the safety and potential health bene- fits of olive leaf extract do not yet exist. Neverthe- less, nonscientific literature is filled with anecdotal accounts of the extract’s ability to heal. It has been available as a dietary supplement in the United States since the mid-1990s. Ruiz-Gutierrez, V. et al. “Oleuropein on Lipid and Fatty Acid Composition of Rat Heart.” Nutrition Research 15, no. 1 (1995): 37–51. olive oil An oil extracted from ground olives. Spain is currently the world’s leading producer of bulk olive oil; Italy is a leading producer of bottled olive oil. The International Oil Agreement was negotiated through the U.N. to ensure olive culti- vation and olive oil production in the Mediter- ranean region. To produce olive oil, crushed olives are mechan- ically pressed several times. The temperature for olive oil extraction can be 50° to 110° F. There is no legal definition of “cold-pressed” oil, but the hotter the pressing, the more oil is extracted. Olive oil is classified as a monounsaturated fat because it contains large amounts of OLEIC ACID,a monounsaturated FATTY ACID with one double bond and lacking two hydrogen atoms—in contrast with polyunsaturates, containing polyunsaturated fatty acids with two or more double bonds and lacking several pairs of hydrogen atoms, and saturates, containing predominantly saturated fatty acids (no double bonds and completely filled up with hydro- gen atoms). Because olive oil is more stable to oxi- dation and rancidity, olive oil is not chemically stabilized (partially hydrogenated). Olive oil, like all oils, provides 14 g of fat per tablespoon, equiva- lent to 120 calories. Proposed Grades of Oil An independent U.S. FDA analysis of 30 imported olive oils revealed that five were not olive oil and 18 were mislabeled as “extra virgin” oil. “Extra virgin olive oil” is prepared from mechanical pressing and is filtered without refin- ing. “Virgin olive oil” is not highly refined and has a golden color and a unique flavor and taste. The 476 olive leaf extract acid content is no more than 1 percent. Virgin olive oil is filtered after pressing and is unrefined; the oil has a rather fruity flavor, and its acid content is less than 2 percent. Oil labeled “olive oil” is usually listed as being “100 percent pure.” It is actually a blend of refined and unrefined olive oil and accounts for about 70 percent of U.S. olive oil con- sumption. Refining involves extraction at high temperatures and with solvents, neutralization of acids, and bleaching. Potential Health Benefits of Olive Oil People who eat predominantly olive oil have lower blood fat and cholesterol and a reduced risk of clogged arteries. Olive oil seems to lower blood levels of the less desirable form of CHOLESTEROL, LOW-DENSITY LIPOPROTEIN (LDL), while raising the level of HIGH-DENSITY LIPOPROTEIN (HDL), the more desirable kind of cholesterol. If the intake of polyunsaturates increases substantially above 7 percent of daily calories, the current average, polyunsaturated oils lower LDL (a desirable effect) but also lower HDL (an undesirable effect). By fol- lowing current dietary guidelines that call for eat- ing less fat (less than 30 percent of total calories) and less saturated fat (less than 10 percent of calo- ries), people necessarily increase their consump- tion of unsaturates. Substituting monounsaturated oils for saturates and polyunsaturated fats and oils may be desirable while decreasing total fat con- sumption because high consumption of polyunsat- urates is more likely to promote the oxidation of LDL cholesterol, the less desirable form, thus increasing the probability that oxidized LDL will be taken up by blood vessels and create plaque in arteries. Furthermore, animal studies suggest polyunsaturates can increase the risk of some forms of cancer. Cooking with olive oil instead of polyunsaturated vegetable oils (safflower oil, corn oil, etc.) may be advantageous because olive oil does not break down as readily when heated. (See also ATHEROSCLEROSIS; CARDIOVASCULAR DISEASE; FAT METABOLISM.) “Special report: olive oil,” UC Berkeley Wellness Letter, 11, no. 9 (June, 1995): 6. omega-3 fatty acids See ESSENTIAL FATTY ACIDS; FLAXSEED OIL. omega-6 fatty acids See ESSENTIAL FATTY ACIDS. onion (Allium cepa) A vegetable with an under- ground bulb closely related to GARLIC and leeks, belonging to the lily family. Onions apparently originated in prehistoric central Asia, and were grown in ancient Egypt, Greece, and Rome, as well as China. There are more than 500 varieties; all of the edible species possess a pungent bulb. Euro- peans introduced onions to the Americas. Today, China, the United States, and India produce the largest yields, and onions rank sixth among veg- etable crops worldwide. Green onions may be harvested before the onion has matured. Alternatively, mature onion bulbs can be harvested. The length of time that dried bulbs can be stored ranges from several days to months, depending on the variety, their stage of maturity, and temperature and humidity during storage. There are two types of dry onion. Flat onions, elongated Spanish onions, and Bermuda onions are usually mild flavored. They do not store as well as globe or late-crop onions, which frequently pos- sess a stronger flavor. The latter store well and can be marketed throughout the year. Onions can be canned, dehydrated, frozen, or pickled. Onions and their relatives possess a complex family of sulfur compounds related to the sulfur- containing amino acid cysteine. Once their layers are cut, the sulfur-containing compounds come into contact with an enzyme called allinase that releases volatile (gaseous) compounds that can irri- tate eyes. Cooking onions and GARLIC modifies these sulfur compounds, and they are not so irri- tating after cooking. The medicinal properties of onions and garlic have been known for thousands of years, and recorded use includes treatment of wounds and infections, tumors, worms and parasites, weakness, FATIGUE, and asthma. Onions resemble garlic in terms of active ingredients and therapeutic effects. The consumption of garlic and onions correlates with lowered blood cholesterol levels. Generally, the higher the dose of garlic and onions, the greater the reduction. Onions also seem to lower blood CHOLESTEROL by helping to block cholesterol syn- thesis. Onions and garlic contain a variety of pun- gent, sulfur-containing compounds. One of these onion 477 [...]... daily The extra 1,000 mg they need to add could come from any one of the following: supplementation with about 1,000 mg of calcium; consuming three cups of milk, two cups of nonfat yogurt, four ounces of cheese, nine ounces of sardines, or four to five cups of cooked broccoli or kale daily These portions of canned fish and vegetables are much more of these foods than most people want in a day Furthermore,... addition of oxygen atoms to carbon atoms and the removal of hydrogen atoms The ultimate oxidation product of carbon compounds is CARBON DIOXIDE Indeed, carbon dioxide in expired air comes from the direct oxidation of FAT, CARBOHYDRATE, PROTEIN, and other fuel molecules by cells in the body Most oxidation takes place in small particles in the cytoplasm known as mitochondria These cellular powerhouses consume... processes, from the contraction of muscle fibers and the transport of nutrients into cells to the biosynthesis of cellular constituents for cell growth and maintenance Only mitochondria possess the enzyme machinery for coupling the flow of electrons to the reduction of oxygen to water, and simultaneously to synthesize ATP Electron transport and ATP production can be uncoupled, that is, oxidations can occur... due to surgical removal of ovaries, and to postmenopause; Cushing’s syndrome (excessive production of GLUCOCORTICOIDS by the adrenal glands); conditions that lead to excessive glucocorticoids, as chronic stress or overmedication with hydrocortisone; and overproduction of hormones from the pituitary gland; and cortisone and thyroid medications; • Certain rare genetic diseases (Marfan’s syndrome, homocystinuria);... acid may be a potential by-product of vitamin C consumption in excess of amounts achievable from dietary sources in cases of kidney disease and of those prone to the formation of calcium oxalate KIDNEY STONES, based on anecdotal reports in a small number of cases Oxalic acid consumption may be a problem for people who are prone to kidney stones, or those who eat a lot of BRAN for fiber and whose diets are... lost from the long bones of the legs, the spine, the jaw bone, the wrists and the ankles when there is not enough calcium in the diet, or when it is poorly absorbed Loss of bone of the spine can lead to compression fractures and a loss in weight frequently associated with aging With reduced bone support, gums may be damaged and teeth may be lost The social and economic impact of osteoporosis is enormous... such nonmodifiable factors as gender, ethnic background, body build, family history of osteoporosis, and age Nevertheless, osteoporosis is one of the most preventable of the degenerative diseases Medical history affects the risk of osteoporosis as follows: • Hormone imbalance Because hormones maintain bone structure, hormonal imbalances can lead to osteoporosis Examples include deficiencies of estrogen... participation is voluntary It is run entirely by volunteers Members of OA focus on getting control of their own lives and identifying underlying emotional issues, not on DIETING, nor on losing weight, nor even on food There are no weigh-ins and no guarantees of weight loss Eating disorder programs managed by hospitals and clinics often send their participants to OA to strengthen their own behavior modification... primarily of muscle and connective tissue Sweetbreads are derived from the thymus gland of young cattle (See also PROCESSED FOOD.) ornithine A nonessential AMINO ACID required in the formation of UREA, the end product of PROTEIN metabolism Ornithine is made by the body Although not incorporated into proteins, ornithine helps the LIVER convert the toxic nitrogen waste AMMONIA to urea via the UREA CYCLE, the. .. women, although alcoholic men are an exception Mineral loss from bones typically begins in the 20s, and 50 percent of the bone loss in women occurs before menopause Postmenopausal osteoporosis (type I) is the most common form; type II osteoporosis occurs with AGING In both men and women, symptoms include curved spine, loss of height, and brittle, accident-prone bones, particularly the spin and hip Calcium . in foods involves the addition of oxygen atoms to car- bon atoms and the removal of hydrogen atoms. The ultimate oxidation product of carbon com- pounds is CARBON DIOXIDE. Indeed, carbon dioxide in. greater the reduction. Onions also seem to lower blood CHOLESTEROL by helping to block cholesterol syn- thesis. Onions and garlic contain a variety of pun- gent, sulfur-containing compounds. One of these onion. back- ground, body build, family history of osteoporosis, and age. Nevertheless, osteoporosis is one of the most preventable of the degenerative diseases. Medical history affects the risk of osteoporosis