To examine whether personality is associated with weight fluctuations over time, for all participants who had at least one valid assessment of personality and two or more assessments of BMI (n = 1,779), we correlated the first assessment of personality with the standard deviation of BMI within individuals over time, controlling for sex, age, age squared, ethnicity, and education. In addition to using this simple standard deviation, we used hierarchical linear modeling (HLM; see below) to estimate the natural logarithm of the total standard deviation within each person. As with the simple standard deviation, we correlated this estimate with personality traits, controlling for the same covariates.
