Obesity

Article Author:
Kiran Panuganti
Article Editor:
Carlee Lenehan
Updated:
10/27/2018 12:31:45 PM
PubMed Link:
Obesity

Introduction

Obesity is the excessive or abnormal accumulation of fat or adipose tissue in the body that may impair health. Obesity has become an epidemic which has worsened for the last 50 years. In the United States, the economic burden is estimated to be about $100 billion annually. Obesity is a complex disease and has multifactorial etiology. It is the second most common cause of preventable death after smoking. Obesity is associated with multiple medical conditions and can cause serious complications of chronic conditions. Obesity needs multiprong treatment strategies and may require lifelong treatment. A 5% to 10% weight loss can significantly improve health, quality of life, and economic burden of an individual and a country as a whole.

Etiology

Obesity is the result of an imbalance between daily energy intake and energy expenditure resulting in excessive weight gain. Obesity is caused by multiple factors which can be genetic, cultural, and societal can be considered common. Other causes of obesity include reduced physical activity, insomnia, food habits, endocrine disorders, medications, food advertisements, and energy metabolism. 

Most common syndromes associated with obesity include Prader Willi syndrome and MC4R syndromes, others like fragile X, Bardet-Beidl syndrome, Wilson Turner congenital leptin deficiency, and Alstrom syndrome are also associated with obesity.

Epidemiology

Nearly one-third of adults and about 17% of adolescents in the United States are obese. According to Center for Disease Control and Prevention (CDC), 2011 to 2012 data, one out of five adolescents, one out of six elementary school age children, and one out of 12 preschool age children are obese. Obesity is more prevalent in African Americans, followed by Hispanics and whites. Southern US states have the highest prevalence, followed by the Midwest, Northeast and the west.

Pathophysiology

Obesity is associated with cardiovascular disease, dyslipidemia, and insulin resistance, in turn, causing diabetes, stroke, gallstones, fatty liver, obesity hypoventilation syndrome, sleep apnea, and cancers.

Association of genetics and obesity is already well established by multiple studies. FTO gene is associated with adiposity. This gene might harbor multiple variants that increase the risk of obesity.

Leptin is an adipocyte hormone which reduces food intake and body weight. Cellular leptin resistance is associated with obesity. Adipose tissue secretes adipokines and free fatty acids causing systemic inflammation which causes insulin resistance and increased triglyceride levels, which subsequently contributes to obesity.

Obesity can cause increased fatty acid deposition in the myocardium causing left ventricular dysfunction. It has also been shown to alter renin-angiotensin system causing increasing salt retention and elevated blood pressure.

Adipocytes have been shown to have an inflammatory and prothrombotic activity which can increase the risk of strokes.

History and Physical

All children six years and older, adolescents, and all adults should be screened for obesity according to the United States Preventative Services Task Force (USPSTF) recommendations.

Physicians should carefully screen for underlying causes contributing to obesity. A complete history should include:

  • Childhood weight history
  • Prior weight loss efforts and results
  • Complete nutrition history
  • Sleep patterns
  • Physical activity
  • Associated past medical histories like cardiovascular, diabetes, thyroid, and depression
  • Surgical history
  • Medications which can promote weight gain
  • Social histories of tobacco and alcohol use
  • Family history

Complete Physical examination Should be done and should include body mass index (BMI) measurement, weight circumference, body habitus, vitals.

Obesity focus findings like acne, hirsutism, skin tags, acanthosis nigricans, striae, Mallampati scoring, buffalo hump, fat pad distribution, irregular rhythms, gynecomastia, abdominal pannus, hepatosplenomegaly, hernias, hypoventilation, pedal edema, varicoceles, stasis dermatitis, and gait abnormalities can be present.

Evaluation

A standard screening tool for obesity is the measurement of body mass index (BMI). BMI is calculated using weight in kilograms divided by the square of height in meters. Obesity can be classified according to BMI:

  • Underweight: less than 18.5 kg/m2
  • Normal range: 18.5 kg/m2 to 24.9 kg/m2
  • Overweight: 25 kg/m2 to 29.9 kg/m2
  • Obese, Class I: 30 kg/m2 to 34.9 kg/m2
  • Obese, Class II: 35 kg/m2 to 39.9 kg/m2
  • Obese, Class III: more than 40 kg/m2

Waist to hip ratio should be measured, in men more than 1:1 and women more than 0:8 is considered significant.

Further evaluation studies like skinfold thickness, bioelectric impedance analysis, CT, MRI, DEXA, water displacement, and air densitometry studies can be done.

Laboratory studies include complete blood picture, basic metabolic panel, renal function, liver function study, lipid profile, HbA1C, TSH, vitamin D levels, urinalysis, CRP, other studies like ECG and sleep studies can be done for evaluating associated medical conditions. 

Treatment / Management

Obesity causes multiple comorbid and chronic medical conditions, and physicians should have a multiprong approach in the management of obesity. Practitioners should individualize treatment, treat underlying secondary causes of obesity, and focus on managing or controlling associated comorbid conditions. Management should include dietary modification, behavior interventions, medications, and surgical intervention if needed.

Dietary modification should be individualized with close monitoring of regular weight loss. Low-calorie diets are recommended. Low calorie could be carbohydrate or fat restricted. A low-carbohydrate diet can produce greater weight loss in the first months compared to low-fat diet. The patient's adherence to their diet should frequently be emphasized.

Behavior Interventions: The  USPSTF recommends obese patients to be referred to intensive behavior interventions. Several psychotherapeutic interventions are available which includes motivational interviewing, cognitive behavior therapy, dialectical behavior therapy, and interpersonal psychotherapy. Behavior interventions are more effective when they are combined with diet and exercise.

Medications: Antiobesity medications can be used for BMI greater than or equal to 30 or BMI greater than or equal to 27 with comorbidities. Medications can be combined with diet, exercise, and behavior interventions. FDA-approved antiobesity medications include phentermine, orlistat, lorcaserin, liraglutide, diethylpropion, phentermine/topiramate, naltrexone/bupropion, phendimetrazine. All the agents are used for long-term weight management. Orlistat is usually the first choice because of its lack of systemic effects due to limited absorption. Lorcaserin should be avoided with other serotonergic medications due to the risk of serotonin syndrome. High responders usually lose more than 5% weight in first three months. 

Surgery: Indications for surgery are a BMI greater or equal to 40 or a BMI of 35 or greater with severe comorbid conditions. The patient should be compliant with post-surgery lifestyle changes, office visits, and exercise programs. Patients should have an extensive preoperative evaluation of surgical risks. Commonly performed bariatric surgeries include adjustable gastric banding, Rou-en-Y gastric bypass, and sleeve gastrectomy. Rapid weight loss can be achieved with gastric bypass, and it is the most commonly performed procedure. Early postoperative complications include leak, infection, postoperative bleeding, thrombosis, cardiac events. Late complications include malabsorption, vitamin and mineral deficiency, refeeding syndrome, dumping syndrome.

Pearls and Other Issues

Management of obesity should also include prevention strategies with physical activity, exercise, nutrition, and weight maintenance.