Association Between Dietary Acid Load and Excess Weight in Adults: A Cross-Sectional Study

Background: Dietary acid load (DAL) influences acid-base balance and has been implicated in chronic metabolic disorders. However, its association with excess weight (EW; overweight/obesity) remains insufficiently studied, particularly in Chinese populations with unique dietary patterns. Clarifying this relationship is crucial for guiding targeted nutritional strategies aimed at reducing obesity and associated metabolic risks in China. Methods: This cross-sectional study analyzed data from 7758 adults in the China Health and Nutrition Survey (CHNS), a multistage, stratified cluster survey. Dietary intake was evaluated using three consecutive 24 h recalls, and DAL was calculated using potential renal acid load (PRAL) and net endogenous acid production (NEAP). The relationship between DAL and EW was analyzed using multivariable logistic regression, with additional insights gained from subgroup analyses and restricted cubic spline (RCS) methods. Results: The final analysis encompassed 7758 individuals, among whom 3072 (39.6%) were diagnosed with EW. After adjusting for all relevant factors, a higher DAL was found to be significantly associated with an increased risk of EW. Individuals in the highest tertile experienced a 27% increased risk associated with PRAL (OR = 1.27, 95% CI: 1.09-1.48, p = 0.002) and a 14% increased risk associated with NEAP (OR = 1.14, 95% CI: 1.01-1.29, p = 0.029), demonstrating a consistent linear trend (p < 0.001). Subgroup analyses showed that the positive association between DAL and EW was particularly evident in men (PRAL: OR = 1.40, 95% CI: 1.12-1.76; NEAP: OR = 1.46, 95%: 1.14-1.85) and in participants younger than 60 years (PRAL: OR = 1.32, 95%CI: 1.11-1.58). Importantly, the association remained significant among individuals without diabetes, hypertension, or heart disease (PRAL: OR = 1.26, 95% CI: 1.08-1.47). RCS analysis further confirmed a linear dose-response relationship between DAL and EW risk. Conclusions: This study establishes a significant dose-response relationship between higher DAL and increased risk of EW in Chinese adults. These findings underscore the potential of diets with lower acid load, particularly those rich in fruits and vegetables, as a strategic approach to mitigating the obesity epidemic.