Mixed

In extremely obese individuals, standard two-compartment body composition models (relying on fixed fat-free mass hydration of 0.738) are inaccurate due to elevated extracellular water, whereas three-compartment models incorporating total body water measurements provide accurate assessments of body fat percentage.

If you are extremely obese (BMI > 40), standard body fat estimates based on simple assumptions (like standard BIA or BMI) are likely inaccurate because your body holds more water in your lean tissue. To track your progress accurately, especially after weight loss surgery, use methods that account for total body water, such as three-compartment models combining air displacement plethysmography (BOD POD) and bioelectrical impedance analysis (BIA).