The prevalence of obesity has dramatically increased during the last 30 years. Data state its occurrence in adults between 20 and 74 years of age increased from 15% in 1976 to 32.9% in 2004.1 During this same time, there was also an alarming increase in weight among children and adolescents. Today, it is estimated that 10% of 2- to 5-year-olds and 15% of 6- to 19-year-olds are overweight. This represents a near doubling of overweight children and tripling of overweight adolescents.1
Obesity is associated with causing or exacerbating conditions such as type 2 diabetes, hypertension, coronary heart disease, stroke, dyslipidemia, gall bladder disease, sleep apnea, some cancers (endometrial, breast, and colon), and osteoarthritis. Although one of the Healthy People 2010 objectives is to reduce the prevalence of obesity among adults to less than 10%, current data indicate that this problem is worsening from year-to-year rather than improving.1 Interventions for its prevention and treatment in all ages are urgently needed.
What causes obesity?
There is no quick answer to this question. The bottom line is that obesity occurs when there is an imbalance between caloric intake and energy expenditure. Nonetheless, there are a variety of factors that play a role in the development of obesity. While in the majority of individuals a single dysfunctional gene is not responsible for causing obesity, it is estimated that genetics contributes to 30% to 70% of the differences in people's weight. Genetics may influence diverse factors, such as the foods a person chooses to eat, athletic abilities that may make exercise easier and more enjoyable, and an individual's metabolic rate.2–4
Another important aspect in understanding the etiology of obesity has to do with the neuroendocrine regulation of appetite. A number of hormones are involved in this process that signal the central nervous system regarding hunger or satiety. An example is leptin, a hormone that is secreted by adipose tissue and interacts with specific receptors in the hypothalamus to reduce food intake and increase energy expenditure.5 Other hormones involved in appetite regulation include ghrelin, thyroid hormones, cholecystokinin, peptide YY, cortisol, and insulin.
The rapidly increasing rate of obesity suggests that behavior and environmental influences are more important causes of obesity than biological factors. Many environmental factors are implicated as major causes of the obesity epidemic. These include the availability of high-caloric fast food and sugar-sweetened soft drinks, large portion sizes, and sedentary lifestyles. Technology has created many time- and labor-saving products (such as elevators, dishwashers, and computers), that reduce the overall amount of energy expended in daily activities. A report from the Surgeon General estimates that 60% of Americans do not participate in regular physical activity, and 25% are almost entirely sedentary despite a growing number of health clubs and homes with exercise equipment.3 Another concern is that physical activity in schools has declined; almost half of young people in the United States between the ages of 12 and 21 years are not vigorously active on a regular basis.
When evaluating an individual who is overweight or obese, it is important to keep in mind that some medications and certain illnesses, such as Cushing disease and polycystic ovary syndrome, may lead to weight gain or obesity.
The most common tool for assessing the degree of obesity is body mass index (BMI). A high BMI generally reflects an increased percentage of total body fat (see Interpretation of BMI scores). Dual X-ray absorptiometry is used for assessing the amount of body fat.2 However, this technique is expensive and impractical for common clinical use. Other methods, such as skinfold measurements, are considered less reliable than BMI and generally are not recommended. BMI may be falsely high in body builders due to their increased muscle mass and falsely low in those with muscle wasting, such as the elderly.2,3,6
Body fat distribution is another important risk factor for obesity-related diseases. Excess abdominal or visceral fat is specifically related to an increased risk of cardiac and metabolic disorders. Precise measurements of visceral fat can be estimated by the use of expensive radiological imaging techniques; however, this is not practical in a clinical setting. Instead, measuring the waist circumference may be used as a marker for abdominal fat mass. A waist circumference greater than 40 inches (102 cm) in men and 35 inches (88 cm) in women places the individual at an increased risk for cardiovascular disease and metabolic disorders, such as type 2 diabetes and dyslipidemia (see Waist circumference measurement protocol).6–8
Obesity is a chronic condition that results in an increase in morbidity and mortality. The clinical problems related to obesity fall into two pathophysiological categories: (1) abnormalities that arise from the increased mass of fat itself, such as osteoarthritis and sleep apnea; and (2) abnormalities that result from metabolic changes associated with excess adipose tissue (such as diabetes mellitus, gall bladder disease, hypertension, cardiovascular disease, and some forms of cancer).9
Obstructive sleep apnea, a form of sleep-disordered breathing, may occur in as many as 50% of those who are morbidly obese.10 This disorder may decrease quality of life and life expectancy, as well as increase the risk for hypertension, stroke, and daytime sleepiness (which can increase the risk for traffic accidents).10 It is thought that fat deposits in the pharyngeal area play a role in the development of this problem.9 Management generally involves weight loss, avoidance of alcohol, and continuous positive airway pressure therapy.
Osteoarthritis, a degenerative joint disease, is a significant problem in overweight and obese individuals. Both the knees and ankles are directly affected due to trauma associated with excess body weight. This may lead to a reduction in quality of life, as well as make exercise more difficult for the patient.
It is well known that type 2 diabetes mellitus is associated with excess weight. A recent study showed that as BMI increased, the risk for diabetes increased such that a BMI of 35 kg/m2 was associated with a 40-fold or 4,000% increase in the relative risk.11 Study participants with a BMI less than 22 kg/m2 had the lowest risk.11 The U.S. Diabetes Prevention Program found that lifestyle modification through caloric restriction, a low-fat diet, and increased physical exercise that resulted in 5% to 7% weight loss reduced the incidence of type 2 diabetes by 58%.11
Investigators also found that increasing weight is associated with an increased incidence of clinically symptomatic gallstones. There is approximately 20 mg of additional cholesterol synthesized each day for every kilogram of extra body fat. This means that for every 10 kg increase in body fat, there is a daily synthesis of cholesterol equal to the amount in one egg yolk. High cholesterol concentrations in bile increase the likelihood that cholesterol may precipitate in the gall bladder, forming stones.9
Obesity is a major risk for two categories of heart disease. The first category relates to the relationship between dyslipidemia and obesity. Obesity is associated with elevated triglycerides and low levels of high-density lipoprotein (HDL) cholesterol, both of which increase the risk for coronary artery disease.12 The second category is related to increased demand for tissue oxygenation, which leads to increased cardiac output. This increase in cardiac work may produce cardiomyopathy and heart failure even in the absence of diabetes, hypertension, or atherosclerosis.9,10
A prospective study of more than 900,000 U.S. adults estimates that obesity may account for 14% of all deaths from cancer in men and 20% of cancer deaths in women.13 Specifically, obese males face an increased risk for colon, rectum, and prostate cancer. In obese women, breast, uterine, and gallbladder cancer is more common. The mechanisms by which obesity may act to increase the risk for cancer are speculative at present, although the increase in breast and endometrial cancer may be due to increased estrogen production by adipose tissue.9,10,14
Obesity can also lead to psychological issues. Those who are considered overweight may be exposed to stigmatization and discrimination. This is particularly seen with obese females potentially due to societal pressure on women to be thin. Recent research also indicates that adiposity and weight gain are risk factors for the development of urinary incontinence in middle-aged women.15
It is important that when evaluating a patient whose BMI indicates they are overweight or obese, consider evaluating for comorbid conditions. Annual screening of fasting blood glucose levels, HDL cholesterol, and triglyceride levels should be noted, particularly where other risk factors are present. Risk factors are include age over 40 years, family history of type 2 diabetes or heart disease, smoking, and a sedentary lifestyle. A weight loss of 5% to 10% of body weight is shown to reduce BP, improve abnormal lipid levels, and reduce the risk of developing type 2 diabetes.
A comprehensive weight loss strategy includes lifestyle modification. This includes dietary changes, exercise, and behavioral changes with a goal of increasing energy expenditure and reducing energy intake. The recommended amount of weight loss is 1 to 2 pounds a week. In some circumstances, limited use of pharmaceutical intervention in conjunction with lifestyle changes is helpful. In patients who are morbidly obese and have comorbid conditions such as type 2 diabetes, surgical intervention may be indicated.16
When addressing weight management with patients, assess their readiness for making necessary changes. One approach may be to ask the patient to rate their commitment on a scale of 1 to 10, with 10 being 100% ready to take action. If the answer is between 1 and 4, the patient has very little intention to lose weight, and prescribing a diet and exercise program would be of little value. If the answer is between 5 and 7, the patient has some ambivalence about taking action to lose weight. The patient may need more information as well as more time for further self-exploration regarding the weight-loss process. If the answer is between 8 and 10, this indicates that the patient is very willing to take action about their weight.6
At this point, discuss the patient's goals or reasons for wanting to lose weight. For some, it may be to enhance theirappearance and to wear fashionable clothes. Others may be motivated by their desire to improve their health and to be able to participate in specific activities. Research indicates that those who diet for health reasons tend to use more healthful strategies for weight loss, such as eating a balanced diet and exercising routinely; they also tend to be more successful.3 It is important to help patients set weight loss goals that are realistic and achievable. Research defines success as achieving and maintaining a 5% to 10% reduction in body weight for at least 1 year.17
Dieting strategies include reducing caloric intake, limiting fat intake, or dietary exchanges (see Key principles for a successful diet). A reduced calorie diet is the cornerstone of dietary management. A caloric deficit of 500 to 1,000 kcal/day may result in a weight loss of 1 to 2 pounds a week. Keeping a daily diary of food intake may be helpful in monitoring caloric intake, particularly for patients who say they eat almost nothing and still cannot lose weight. A diary may help them see that they eat more than they thought, and may also assist in identifying specific triggers for overeating.3,18,19 One randomized trial that compared various diets—Atkins (carbohydrate restriction), Ornish (limiting fats and emphasizing unprocessed foods), Weight Watchers (limiting calories), and the Zone Diet (emphasizing a 40:30:30 ratio of carbohydrates to proteins to fats)—indicated that each diet resulted in moderate weight loss as well as reduced risk factors for heart disease.20
Other behavioral strategies helpful in reducing calorie intake are to avoid watching television or reading while eating, and to identify triggers associated with increased caloric intake. For example, if stress or worry is the stimulus for eating, advise the patient to make a list of alternative relaxing or stress-reducing activities. It is vital that patients trying to lose weight monitor portion size. A press release summarizing a survey by the American Institute for Cancer Research stated that most people in the United States believe the kind of food they eat is more important for managing weight than the amount of food they eat.21 One study found that the average portion of a single serving of cooked pasta was 480% greater than the recommended serving size.21 Patients need to be educated regarding what constitutes a normal size portion with a focus on the need to consume smaller portions.
Physical activity should be a part of every weight loss program. Exercise not only helps increase energy expenditure, but improves comorbid conditions such as BP and glucose tolerance. Evidence indicates that diet alone achieves greater weight loss than physical activity alone, but physical activity is associated with helping to maintain weight loss. Physical activity recommendations suggest a minimum of 30 minutes of moderate-intensity activity on at least 5 days of the week. The CDC defines moderate-intensity activity as anything that causes small increases in breathing or heart rate. An example of moderate-intensity exercise is brisk walking. A pedometer or a step counter may be an effective motivator for some patients with a goal of walking 10,000 steps each day. It is important to note that exercise does not need to occur in a single session to be effective, but can occur in divided sessions throughout the day (although the American Heart Association guidelines recommends a minimum of 10 minutes per session). For some patients, knowing this information may improve compliance.3,18,22–25
Exercise adherence rates average around 50%. Therefore, when prescribing an exercise program, address potential barriers that may interfere with the patient achieving success with the recommended exercise program. The barriers most often mentioned are lack of time for exercise or being too tired. One solution that may be suggested is to divide exercise into 10-minute increments: 10 minutes before work, 10 minutes during lunch, and then 10 minutes after work. Another barrier may be that the patient cannot afford the cost of a health club membership or purchasing exercise equipment. Suggest that the patient use cans of food for weights, check out exercise videos from the local library, or tune into an exercise show on television. Some patients feel unsafe walking in their neighborhood. Possible solutions for this barrier include mall walking or joining an exercise group at the local community center. The bottom line is that we must educate patients about the need to incorporate physical activity into their daily routine by providing specific and realistic prescriptions for exercise.
Weight-loss medications may be used as an additional component of a comprehensive weight loss program. Pharmacotherapy is indicated in patients with a BMI of 30 kg/m2 or greater, or patients with a BMI of 27 kg/m2 or greater and one comorbid condition related to obesity (such as hypertension and type 2 diabetes). Drug efficacy should be evaluated in regard to reduction in BMI, a decrease in waist circumference, improvement in risk factors, and disease improvement.
At this time, only two prescription drugs are FDA- approved for long-term treatment of obesity. This first is sibutramine (Meridia), an agent that promotes satiety by inhibiting the reuptake of norepinephrine, serotonin, and dopamine; and the second is orlistat (Xenical), an agent that decreases intestinal fat absorption by inhibiting the intestinal enzyme lipase (see Medications for obesity management). Beyond that of lifestyle modification, these drugs produce an additional weight loss of 5% to 10% over 1 year. Both drugs result in improvement in lipid profiles and fasting glucose levels. It is important to emphasize with patients that once therapy is stopped, many patients regain weight unless lifestyle modification occurs.5,18,26–27
For patients with morbid obesity, weight reduction surgery may be considered. Surgery is recommended only for patients with a BMI of 40 or greater, or a BMI of 35 or greater with the presence of obesity-related comorbid conditions. The National Heart, Lung, and Blood Institute guidelines endorse weight-loss surgery only when less invasive methods of weight loss fail.6 There are two major categories of surgical procedures: 1) a combination malabsorptive/restrictive, and 2) restrictive. Both can be accomplished with laparoscopic techniques and require life-long medical monitoring.
Malabsoptive/restricitive procedures (such as Roux-en-Y gastric bypass) involve bypassing the majority of the stomach and the upper portion of the small intestine. Weight loss is caused by altering absorption of nutrients and more rapid satiety. After the immediate postoperative period, a major complication associated with this type of surgery is vitamin and mineral deficiencies—patients are required to be on life-long vitamin and mineral supplementation. Restrictive procedures include vertical banded gastroplasty and adjustable gastric banding. In vertical banded gastroplasty, the size of the stomach is surgically reduced using a vertical row of staples across the stomach. A band is placed that decreases the opening of the upper pouch. This delays gastric emptying and results in the patient feeling full after eating a small amount of food. Adjustable gastric banding entails placing an inflatable band encircling the top portion of the stomach. Weight loss is achieved by restriction of the passage of mainly solid foods. Discomfort, involuntary vomiting, or both can occur after poor chewing, rapid eating, eating too much at one time, or drinking shortly after eating.
Surgery results in a greater magnitude of weight loss when compared to other interventions with a mean weight loss of 61 to 100 pounds. Postoperative mortality is low, with one surgery related death in five studies (˜650 patients). Postoperative morbidity occurred in less than 5% of patients, and was usually a result of infection or pulmonary complications. Other than weight loss, these procedures improve both comorbidities and quality of life.2,6,16,29
A life-long commitment
Successful weight management requires a life-long commitment to healthy behaviors. Strategies must include both prevention and treatment approaches. According to the National Weight Control Registry, strategies that help individuals and registry members to keep the weight off include a low-calorie, low-fat diet; exercising about 1 hour per day; eating breakfast every day; weighing themselves at least once a week; and watching less than 10 hours of television per week.30 As NPs, we are in an ideal position to effectively help patients manage healthy lifestyle changes to prevent obesity-related diseases.
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