Ideal Weight (Hamwi)

About Ideal Weight (Hamwi)

The Hamwi formula, developed by G. J. Hamwi and colleagues and presented in 1964 in the context of diabetes and nutrition management, is one of the earliest ideal body weight formulas and remains in use, particularly in diabetes education and dietetic practice. Hamwi's approach was designed to give practical weight targets for adults with diabetes, for whom weight management is central to glycemic control, and the formula was later generalized for nutrition assessment in broader populations.

How the formula works

The Hamwi formula uses the same base-plus-increment structure as the other IBW formulas but with distinctive coefficients. For men: IBW = 48.0 + 2.7 x (height in inches - 60). For women: IBW = 45.5 + 2.2 x (height in inches - 60). The base weight at 5 feet is 48.0 kg for men (the lowest of the four major formulas) and 45.5 kg for women (tied with Devine). The per-inch increment is 2.7 kg for men (the highest of the four) and 2.2 kg for women. This steep slope produces ideal weights that rise rapidly with height, giving the highest estimates of the four formulas for tall men and the lowest for very short men.

Evidence and comparison

Hamwi's formula was derived from clinical nutrition experience rather than formal regression, similar to Devine. A 2007 comparison by Shah and colleagues found that for a 175 cm (5 foot 9 inch) man, Hamwi predicts about 76.5 kg, slightly higher than Devine (73 kg), Robinson (72.5 kg), and Miller (71.5 kg). The Hamwi formula is notable for its steep slope, which produces the widest spread between short and tall adults among the four major IBW formulas.

Interpretation

The Hamwi formula gives ideal weights that correspond to a BMI of approximately 23 for average-height adults, slightly higher than the other formulas. The Hamwi approach also traditionally includes frame size adjustments: add or subtract a percentage (often 10 percent) for large or small frames, and for women the original Hamwi method adds additional increments for height above 5 feet in a slightly different structure than the simplified formula used here. The formula is commonly used in diabetes education to set weight-loss targets for patients with type 2 diabetes.

When to use it

The Hamwi formula is used primarily in diabetes and nutrition education settings, where it has a long history of use for setting weight-management targets. It is also included as one of several IBW options in many nutrition assessment tools. Because the differences among the four major formulas are modest for average-height adults, the choice is often a matter of institutional convention or personal preference.

Limitations

Like all IBW formulas, Hamwi's equation does not account for frame size, age, body composition, or muscle mass, and it was derived from clinical experience rather than formal population regression. The steep slope produces the highest ideal weights for tall adults among the four major formulas, which may overestimate healthy weight for tall individuals with small frames. The formula should not be used for children, pregnant women, athletes, or the very elderly without adjustment. For contemporary applications, BMI-based ideal weight or body-composition-based targets are often preferred, but the Hamwi formula remains a useful and historically important reference, particularly in diabetes care.