A study done by Norwegian University of Science and Technology shows that people with BMI under 30 kg/m2 are not at risk of kidney disease even if they have prehypertension (Systolic ressure 120-149 mmHG, and diastolic BP 80-89 mm Hg). More than 30% of Americans and Europeans can be classified as prehypertensive.
The 75,000 participants in the study were found to have strong links between blood pressure and body weight. However, only the prehypertensive participants with BMI of 30 kgm2 and over increased their risk of ESRD or CKD-related diseases.