What is ideal body weight (IBW)?

It refers to the body weight associated with the lowest mortality for a given sex and body frame. (Ideal body weight is the optimal weight associated with maximum life expectancy for a given height.) The data come from surveys by the Metropolitan Life Insurance Company and denote the range of weights at a given height (for a given sex and frame) that is associated with the lowest mortality.

It means an ideal body weight calculated from height; it is used for drug dosing, nutrition prescriptions, and assessment of kidney function, among other uses. Because it is derived from height, it reflects lean mass more than body fat.

Formulas for ideal body weight (IBW)

(1) Devine formula

IBW (men) = 50 kg + 2.3 kg × (height [in] − 60)

IBW (women) = 45.5 kg + 2.3 kg × (height [in] − 60)

※ Adjusted body weight (ABW)

In people with obesity, using actual body weight as-is can lead to overdosing of medications and overestimation of nutrition metrics. (Adipose tissue has lower metabolic activity and does not scale exactly with the volume of distribution of drugs.) Therefore, ABW is a weight adjusted to somewhere between IBW and actual body weight. As the formula below shows, it effectively credits only about 40% of the difference between actual weight and IBW.

ABW = IBW + 0.4 × (actual body weight [kg] − IBW)

(2) Percent of ideal body weight (PIBW)

IBW (men) = height [m] × height [m] × 22

IBW (women) = height [m] × height [m] × 21