Objective: We evaluated the association between periconceptional dietary diversity, reflected by evenness in energy distribution across foods, and metabolic syndrome risk at 3 years postpartum and whether this association differs by diet quality.

Methods: We analyzed data from 4025 participants in Nulliparous Pregnancy Outcomes Study: monitoring mothers-to-be Heart Health Study. Periconceptional dietary intake was assessed using a food frequency questionnaire. Dietary diversity was operationalized as energy distribution evenness across foods using Pielou’s Index. Multivariable logistic regression was used to estimate the association between energy evenness and incident metabolic syndrome (defined using AHA/NHLBI criteria), adjusting for total energy intake and maternal characteristics. We stratified analyses using Healthy Eating Index-2020 scores representing lower (HEI <60) and higher (HEI ≥60) diet quality.

Results: Periconceptional energy evenness differed by diet quality. Among those with lower-quality diets, participants with energy intake more evenly distributed across foods had a lower percent energy from sugar-sweetened beverages (e.g., regular soda: 2.1% vs. 7%) and a higher percent energy from many refined grains and fat sources (e.g., bagel: 2.3% vs. 1.6%; butter: 1.5% vs.1%) compared to those with energy concentrated in fewer foods. Percent energy differences were minimal in higher-quality diets. Postpartum metabolic syndrome occurred in 14% of participants (n=602). Among those with lower-quality diets, the adjusted risk of metabolic syndrome was stable until approximately the median of energy evenness and then increased steadily. No association was observed among those with higher-quality diets.

Conclusions: Among individuals with suboptimal periconceptional diets, high energy evenness may indicate dispersion of energy intake across many nutrient-poor, energy-dense foods, potentially increasing postpartum metabolic syndrome risk.