LMI vs BMI: What's the difference?

LMI (lean mass index) and BMI (body mass index) categorize people based on height and weight. But BMI only accounts for your total body weight, whereas LMI considers your body composition.

LMI is generally a more accurate tool for lean and active people and is better for finding your ideal weight.

Because BMI does not distinguish between fat mass and muscle mass, a person with higher muscle mass and low or normal fat mass can be misclassified as overweight or obese. LMI can more accurately classify this individual as having higher muscularity instead of overweight or obese.

Similarly, a person with low muscle mass and higher body fat mass could be classified as normal weight according to BMI when in reality they are what is called normal-weight obese. LMI would help identify their low muscle mass and higher fat mass.

LMI has gender-specific reference ranges that make it a more useful metric than BMI which is not age or gender specific. Men and women have different normal thresholds and capacities for fat mass and lean mass so having a gender-specific measure is important for properly evaluating status.

A combination of LMI and FMI (fat mass index) can help determine whether a person should focus on fat loss, muscle building, or both when setting their health and fitness goals.