Objective: To compare interrelationships between different indices and their relationship with cardiovascular disease risk factors.
Method: Longitudinal comparison among weight change indices in the observation of a fixed population from age 21-40.
Subjects: 215 non-obese blue-collar workers in a steel company.
Measurements: Systolic blood pressure, diastolic blood pressure, serum cholesterol, serum uric acid, past history of illness, present illness, body mass index (BMI: weight/height2 (kg/m2)), indices of weight change (the intrapersonal standard deviation of BMI (ISD), the coefficient of variation of BMI (CV), the root mean square error of variation (RMSE) around the slope of BMI vs age, weight change categories (cycler, weight gainer, no changer, etc.), and number of weight cycles (NWC: one cycle is defined as 5% weight loss and 5% weight gain)). Indices were calculated using yearly and five-yearly measurements of weight for analyses.
Results: The average RMSE distinguished large cyclers from other weight change categories, while ISD and CV did not. The correlation between ISD and CV was strong and significant. That between RMSE and ISD (or CV) was moderate and significant. Among the weight change categories, no weight change group included many actual weight cyclers. As for the relationship with coronary risk factors, no significant change in risk was noted in cyclers as determined by NWC or weight change category. The top one third of ISD and the top one third of CV was related with elevated risk of "any risk factor,' but at a lower level of significance.
Conclusion: ISD and CV reflect almost the same aspects of weight change, but the other indices reflect different aspects. When investigating the relationship between coronary risk factors and weight variability (especially, weight cycling) among young adult non-obese men, it is preferable to use weight change patterns such as NWC and weight change categories, or RMSE in conjunction with or in place of CV (or ISD).