Background: The influence of genetics on obesity is well established. Adoption studies and twin studies suggest that about 80% of the obesity risk is genetic. We designed a tool to predict outcomes of treatments in patients with sporadic or familial obesity.
Methods: Two factors best correlate with multifactorial genetic risk: 1) familial history and 2) age of onset. 147 morbidly obese adults self- or physician-referred for possible surgery for morbid obesity (age 17-66 y, BMI 35-82) were studied. Six elements were selected to measure the genetic influence on patients' weight: 3 personal weight milestones (weight at age 10, 20 and 30), and 3 family history factors (parents' weight, siblings' weight and second degree relatives' weight. These 6 elements of personal and family history information were collected prospectively on 35 obese patients and a feasible scoring system devised, with 0 points signifying no genetic component and 100 points suggesting the maximal possible genetic risk for obesity. Prospective data were then collected on 147 consecutive patients seen in consultation for possible bariatric surgery, to provide this "obesity risk index" (ORI).
Results: The final scoring system for the ORI assigned 50 possible points for personal weight milestones and 50 possible points for family history factors. At age 10, patients receive 10 or 20 points for being 2 or 3 SD above the mean BMI for age, respectively. At age 20, 10 or 20 points are received for BMI > 30 or 40, respectively. At age 30, 5 or 10 points are received for BMI > 35 or 50, respectively. 0 to 28 points are awarded for parental obesity, with 7 or 14 points for each parent with BMI > 30 or 40, respectively. The mean BMI of all siblings was calculated, with 6 or 12 points received for mean BMI greater than 30 or 40, respectively. Two points are awarded for each second degree relative with BMI > 35, to a maximum of 10 points. The mean (+/- SEM) score for our first 114 patients was 32 +/- 2 (range 0 to 87). The median score was 28.13% of patients had scores < 10; conversely, 13% scored points on all 6 elements.
Conclusion: An ORI has been devised to quantify the genetic contribution to an individual's weight. Using this scoring system, we found that about 85% of patients who are candidates for bariatric surgery have elements in their history to suggest a genetic risk for morbid obesity. About 15% have extremely strong genetic ORIs.