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Percentage BMI Change (ΔBMI%)

Summary

Percentage BMI Change ($\Delta BMI\%$) is a normalized metric used in clinical and epidemiological studies to quantify weight changes over time. By calculating the change relative to baseline BMI, it allows for cross-patient comparison regardless of initial body size or height. This metric was utilized as the primary efficacy phenotype in the GWAS of GLP-1 Receptor Agonists response conducted by the Auton Lab.

Formula and Calculation

The percentage BMI change is calculated as: $$\Delta BMI\% = \frac{BMI_2 - BMI_1}{BMI_1} \times 100$$

Where: - $BMI_1$ is the baseline (pre-treatment) body mass index ($\text{kg/m}^2$). - $BMI_2$ is the post-treatment (or current) body mass index ($\text{kg/m}^2$).

Since adult height is assumed to be constant during treatment intervals, $\Delta BMI\%$ is mathematically equivalent to the percentage change in body weight ($\Delta\text{weight}\%$).

Applications in Pharmacogenetics

In GWAS of anti-obesity medications (such as semaglutide and tirzepatide), $\Delta BMI\%$ serves as a quantitative trait to identify genetic associations with drug efficacy. In the study by Su et al. (2026), covariates included in the linear models for $\Delta BMI\%$ were age, sex, baseline BMI, drug type, dosage, and days on treatment to adjust for non-genetic confounding factors.

Citations