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Background: Obesity is a global public health issue with increasing prevalence and notable differences across population. Previous studies on body mass index (BMI) trends and inequalities have focused on overweight/obesity prevalence or average BMI changes, overlooking differences across the BMI distribution. This study investigates whether changes in BMI distribution are uniform or different over time and educational attainment.

Methods: This study is based on repeated cross-sectional surveys in Västerbotten, Sweden. Study participants were expectant parents visiting antenatal care (2010–2019) as part of the Salut Programme. During early pregnancy, 18,215 women and 17,890 male partners completed questionnaires. Quantile regression analyses were conducted to assess BMI distribution changes over time and by education for men and women.

Results: The BMI distribution for women showed a sharper increase in the upper tail in 2018/19 compared to 2010/11, whereas for men, the upper tail showed a gradual rise over years. Similar changes in BMI distributions were observed over time across both educational groups, with a notable increase in the higher BMI segments.

Conclusion: The study revealed weight gain inequalities, with higher BMI segments experiencing a disproportionately higher rise compared to others. Identifying high-risk groups in vulnerable settings will better equip decision-makers to design and implement targeted intervention strategies to reduce overweight and obesity.