Objective: The objective of this study is to gain insights into the influence of income on the body mass index (BMI) locus in the elderly population. Methods: The Chinese Longitudinal Healthy Longevity and Happy Family Study (CLHLS-HF) was included at baseline (2008) for participants aged 65 years and older. The total number of participants analyzed in this study was 7555. A population-based trajectory model (GBTM) was used. The economic income level was an independent variable and adjusted for age, gender, ethnicity, education, marriage, and physical activity (Model 1), and the baseline BMI value was added in Model 2, with a quadratic of the income added in Model 3. A sensitivity analysis was adopted. Results: Three BMI trajectory groups were identified using GBTM and were labeled as “overweight”, “normal”, and “obesity”. After adjusting for covariates (Model 1), with the increase in economic income, the risk of the elderly transitioning into the overweight trajectory group and the obesity trajectory group was relatively increased. When the baseline BMI values were adjusted for Model 2, the effect of economic income on the overweight and obesity trajectories was enhanced. A sensitivity analysis was performed, and it was found that the result of the positive impact of economic income on the BMI trajectory group was robust. Conclusions: The higher the income, the greater the risk of Chinese elderly individuals developing the overweight or obesity trajectory. It is suggested that elderly individuals with higher economic income especially need interventions and nutrition education to help them acquire nutrition knowledge for a healthy lifestyle. The positive impact of economic income on the BMI trajectories of the elderly provides further directions for preventing and controlling obesity in the elderly.
