Association between the Chinese diet balance index 2022 and the risk of metabolic syndrome: a cross-sectional analysis in middle-aged and older adults.

Metabolic syndrome (MetS) represents a major public health challenge, yet evidence regarding the relationship between diet quality, as evaluated by the Chinese diet balance index 2022 (DBI-22), and the risk of MetS remains limited. This cross-sectional study aimed to investigate the association between DBI-22 and MetS among middle-aged and older adults. 3,503 participants aged ≥ 45 years in Guangzhou, China, were included. Dietary intake was assessed using 3-day 24-h records, from which the DBI-22 indicators, including high bound score (HBS), low bound score (LBS), and diet quality distance (DQD), were categorized into two tiers. MetS was defined according to the Joint Interim Statement. Multivariable logistic regression was employed to estimate odds ratios (ORs) and 95% confidence intervals (CIs), and restricted cubic splines were used to examine nonlinear associations. Compared to suitable LBS, unsuitable LBS was associated with higher odds of MetS (OR = 1.28, 95% CI: 1.07-1.54; p-trend = 0.008). Unsuitable DQD was associated with higher odds of MetS (OR = 1.28, 95% CI: 1.07-1.52; p-trend = 0.006), elevated waist circumference (OR = 1.24, 95% CI: 1.02-1.50; p-trend = 0.031), and elevated blood pressure (OR = 1.20, 95% CI: 1.03-1.40; p-trend = 0.020). A nonlinear relationship was identified between LBS and low HDL-C (p-nonlinear = 0.034), with an inflection point of 17.8. Participants with MetS showed higher rates of severe dietary inadequacy and imbalance. These findings suggested that dietary insufficiency, rather than excess, was significantly associated with MetS, emphasizing the importance of promoting protective food intake in this population.