Rationale:

• A high BMI and/or increased central adiposity increases the risk of health problems and impairs the quality of life.
• Weight loss may improve metabolic cardiac risk factors and lifestyle.

Evidence:

• Obesity carries a social stigma (157).
• Obesity and 20 years of aging have similar impact on chronic ill health and more impact than smoking or problem drinking (158; 159). Disability-free life expectancy is greatest among subjects with a BMI of 25 to <30 kg/m² (160). In a study from India, BMI and all forms of tobacco use had independent effects on mortality risk (161).
• Longitudinal epidemiological studies show that higher relative weight or BMI increases risk of death at BMI >25 kg/m² in young and middle-age adults (162; 163; 164; 165; 166; 167; 168; 169; 170; 171; 172), and in women (173), but BMI is a weaker predictor in older adults (174; 175; 176).
• Avoiding being overweight is among the factors leading to long life in Japanese-American men (177) because obesity increases all-cause mortality (178). A study of a Japanese population established an optimal BMI of 23.4 to 25.3 kg/m² for men and 21.6 to 23.4 kg/m² for women (179).
• The risk of type 2 diabetes mellitus increases rapidly at higher BMI (128; 172; 180; 181; 182; 183) and abdominal adiposity (184). The presence of type 2 diabetes mellitus increases congestive heart disease mortality (185). Low cardiorespiratory fitness and higher BMI are independently associated with onset of diabetes (161; 186).
• Sweetened beverage consumption increases the risk of CHD in women (187).
• Weight gain, independent of attained weight in middle age, increases risk of impaired glucose tolerance (188).
• Risk of death (134; 189), cardiovascular disease (134; 190), cancer (134), and diabetes (191) is higher with central body fat.
• A higher BMI (127; 192; 193; 194), as well as weight gain in adult life (127), is associated with a greater risk of heart disease and stroke (169; 172; 195; 196; 197), independent of cholesterol and blood pressure (198), congestive heart failure (199), and atrial fibrillation (200; 201). The risk for congestive heart failure may relate to the increased insulin resistance (202). In one study, risk for major cardiovascular disease increased 6% for each 1.1 kg/m² increase in BMI (203).
• Abdominal adiposity increases the risk of coronary heart disease (133; 204; 205; 206), sudden death (207), and stroke in men, but not women (197) or in both (172); it increased the risk even after using Framingham prediction scores (208). In contrast, higher hip circumference (adjusted for BMI and waist circumference) predicted less CHD and type 2 diabetes (209).
• A higher BMI is associated with kidney stones (210), albuminuria (211), chronic renal disease (212; 213; 214; 215), risk of end-stage renal disease (216; 217), and renal cell carcinoma (218; 219; 220). Metabolic syndrome is an independent predictor of chronic kidney disease (221).
• In a meta-analysis, obesity was associated with a longer ICU stay, but there was an apparent inverse association with mortality in critically ill patients (222).
• The risk of liver disease (172), gall bladder disease (223), gallstones (224), cholecystectomy (225), nonalcoholic steatohepatitis (226), gastrointestinal reflux disease (227), erosive gastritis (227), Barrett's esophagus (228), and esophageal adenocarcinoma (227) increases as BMI increases (223).
• Hypertension is linearly related to BMI (229; 230; 231) and increases the risk of cardiovascular disease and stroke (172; 232).
• Risk of stroke is increased in Japanese men and women (233) and Finnish men with the metabolic syndrome (234) and in Chinese men with a BMI >25 kg/m² (135).
• Dyslipidemia characterized by a low HDL cholesterol and high triglyceride level are more common in obesity with central adiposity (235), are criteria for the metabolic syndrome (236), and predict coronary heart disease (237).
• Pulmonary disease (172), including sleep apnea (238), pulmonary embolism (239), venous thromboembolism (240), sleep-disordered breathing (241), and possibly asthma (242; 243) are associated with higher BMI.
• Sleep apnea may result in part from increased pharyngeal fat deposits and can lead to respiratory and cardiovascular problems (238).
• Osteoarthritis and hospitalization for back disorders are increased with higher BMI (244; 245; 246; 247; 248; 249).
• Pregnancy complications increase as BMI increases (250; 251; 252).
• Infertility increases with BMI (253).
• Obese men have an increased risk of cancer (172), including multiple myeloma, cancer of the liver, pancreas, stomach, esophagus, colon (220; 254; 255) and rectum, gallbladder, and kidney (256; 257). Obesity plays a role in lymphohematopoietic malignancies (258), including Hodgkin's disease (259) and myelodysplastic syndromes (260).
• Obese women have increased risk of multiple myeloma; non-Hodgkin's lymphoma; and cancer of the uterus, kidney, cervix, pancreas, esophagus, gallbladder, breast, liver, ovary, and colon and rectum (220; 256; 261).
• Increased percent body fat resulted in an increase in deaths from colorectal cancer (262).
• Being overweight lowers physical and emotional functioning in children (263) and in adults (264; 265); weight loss improves health-related quality of life (266; 267). In persons over 65 years, obesity is associated with impaired physical functioning but not greater mortality (268).
• Prospective cohort studies provide a moderate level of evidence relating obesity to future risk of depression. Cross-sectional studies from the U.S. related obesity to depression but studies from other countries do not (269).
• Obesity in young adulthood increases disability pensions (270), and mid-life obesity increases health costs between the ages of 65 and 85 (271), the risks of hospitalization (272), and the risk of nursing home admission (273). Obesity increases the risk of morbidity and mortality among patients in the ICU (274).
• Risk of diabetes is reduced in older adults who are more physically active, eat better, never smoked, use alcohol only moderately, and have a BMI <25 (275).
• In a randomized, controlled trial of 110 obese men, weight loss improved erectile function in approximately one third of the intervention group (276).
• Reducing body weight alleviates comorbid risk factors (98; 151; 277; 278; 279; 280) and lowers mortality (281; 282).
• Weight change of ±15% during 1 year after determination of BMI in women aged 50 to 66 years did not change 17-year mortality (283).
• Weight cycling among women in the Nurses Health Study was not detrimental (156).
• High BMI (40 kg/m²) increases risk of mortality among long-term ICU admissions (284), but not in another (285) although length of stay and use of mechanical ventilators was prolonged.
• Two reviews discuss the role of weight loss in reducing metabolic syndrome (286).

Comments:

• If obesity or its comorbidities persist after weight loss, consider treating comorbidities with appropriate medications.