Introduction How body image perception (BIP) influences changes in Body Mass Index (BMI) in adult women has not been evaluated.

Objective To assess BMI-changes over a 3-year period and their relationship with BIP in a Chilean women population-based cohort.

Methods Weight and height were measured at baseline (32.0±7.0 y) and at follow-up in 510 women participants in the GOCS study. BMI was used to classify women in normal (≤25 kg/m²), overweight (>25 kg/m²), or obese (>30 kg/m²). BIP was self-assessed at baseline using the Stunkard Figure Rating Scale (nine figures from very thin to very obese). BIP-discrepancy was defined as the disagreement between measured-BMI and assigned-BMI of the selected figure (defined on a previous validation study). Multivariate linear regression was used to assess the influence of BIP on BMI-changes stratifying by nutritional status and controlling for potential confounders (ie, parity, schooling, age).

Results At baseline, 61% had excess weight (37% overweight and 24% obese). In 3 years, this number increased to 70% (38% overweight and 31% obese). One out of 4 increased their BMI category, particularly normal women (28.9% from normal to overweight and 22.5% from overweight to obesity). At baseline, BIP-discrepancy was 66% and was associated to concurrent BMI only in obese (p-for-interaction <0.05; coefficient_{all sample}=0.48; 95% CI −0.49 to 1.45; coefficient_obese=1.65, 95% CI 0.03 to 3.28). BIP-discrepancy was unrelated to the 3-year changes in BMI (p-for-interaction >0.05, coefficient =−0.45, 95% CI −0.95 to 0.04).

Conclusion In 3 years we observe a large BMI increase among young women of a post-transitional country. Body size misperception does not explain this large increase. Population strategies are needed to stop this detrimental trend.