The relationship between body mass index (BMI) and the percentage of corporal fat (PCF) and the risk factor according to the waist/hip index (W/H) was studied in 326 adults. With the BMI we observed non-obese adults with a high levels of risk due to W/H ratio and obese individuals with an W/H ratio not indicating high risk. The comparison between PCF and W/H ratio indicated that we have non-obese men with an W/H ratio of high risk and obese individuals with an acceptable W/H ratio, predominant number of obese women with an acceptable risk of W/H ratio. It is evident that even adjusting the cut of point for BMI and PCF, the will always be false positives and false negatives in a considerable proportion, if for the predictions of risk associated to obesity we use only indicators of total fat and corporal mass. At population level, the combination of the BMI and the W/H ratio, could be the election mark for screening of risk in some chronical degenerative illnesses non-transmissible in adults.