Bariatric surgery has gained popularity as a useful tool in the fight against obesity. Weight loss surgeries approved by the Center for Medicare and Medicaid Services, or CMS, include Roux-en-Y gastric bypass, or RYGBP; laparoscopic adjustable banding, or LAGB; and biliopancreatic diversion with duodenal switch, or BPD/DS. However, these surgeries are only approved when certain conditions are met, including an appropriate body mass index, or BMI.
Determining Body Mass Index
Body mass index is a method of evaluating body fatness by comparing the ratio of body weight to height squared. To determine BMI, simply divide weight in kilograms by height in meters squared. Alternatively, multiply weight in pounds by 703 to assess BMI. Divide that number by height in inches, and divide the result by height in inches again. If a computer is available, BMI tables and online BMI calculators allow assessment without requiring calculations.
Evaluating Body Mass Index
Based on the BMI obtained, an assessment of body fat can be made. The BMI classification for adults is defined by fixed cut-off points: a BMI of less than or equal to 18.5 is considered underweight; 18.6 to 24.9 is considered normal weight; from 25 to 29.9 is considered overweight; 30 to 34.9 is class I obesity; 35 to 39.9 is class II obesity; and above 40 is class III obesity. Above 25, BMI is correlated with increased morbidity in populations. Although BMI only compares weight to height and not composition of weight, some individuals may be overweight but not overfat and vice versa. Further, this assessment applies only to adults. Children and the elderly should be assessed by their primary care providers
BMI and Bariatric Surgery
The risk of certain diseases increases as BMI increases. Obesity-related comorbidities include, but are not limited to, diabetes, heart disease, sleep apnea, osteoarthritis, infertility and high blood pressure. As BMI reaches 40 and higher, there is a sharp increase in incidence of these comorbidities, and they are improved with weight loss. Conventional methods have not been proven effective for sustained weight loss. Surgical interventions that alter the gastrointestinal tract are deemed the most effective means of achieving meaningful weight loss in those with a BMI of over 40. Therefore, a BMI of 40 or more is required to qualify for bariatric surgery. Weight loss surgery is also covered and approved by insurance companies for some individuals with a BMI of 35 or higher if they have significant obesity-related comorbidities including diabetes, sleep apnea, and heart disease. In spite of attempts to have bariatric surgery approved as a treatment for diabetes in those with a BMI under 35, CMS has determined that there is insufficient evidence to support improved health outcomes in those patients, and they are not eligible for bariatric surgery.
A BMI Too High for Surgery
A higher BMI may be associated with greater surgical risks, including incisional hernia, poor wound healing and pneumonia. However, according to a two year retrospective published in January 2010 in "Surgical Endoscopy," a comparison of patients with BMIs greater than 60 and those having a BMI of less than 60, showed no difference in surgical outcomes. The maximum BMI that is safe and feasible will depend on where the fat tissue is located and comorbidities, as well as the surgeon's policy. Losing weight before surgery may improve surgical outcomes by reducing fatty liver.
References
- Center for Medicare and Medicaid Services
- Weight-Control Information Network
- The Practical Guide: Identification, Evaluation, and Treatment of Overweight and Obesity in Adults, National Heart, Lung and Blood Institute
- "Surgical Endoscopy"; Is BMI greater than 60 kg/m(2) a predictor of higher morbidity after laparoscopic Roux-en-Y gastric bypass?; Kushnir L.; January 2010
