Change in body weight and body image in young adults: a longitudinal study.

Background: The goal of this study was to identify the effect of the change in body mass index (BMI) from childhood to adulthood on body image satisfaction at 23 years of age in members of the 1982 Pelotas Birth Cohort in Pelotas, RS, Brazil.

Methods: The study used data from the 1986 and 2004-5 follow-up studies. Body shape satisfaction was evaluated using the Stunkard scale. Body shape dissatisfaction was defined as the difference between the figures chosen for the current and ideal body size. BMI z-score changes were calculated as the difference between z-score values at 4 and 23 years of age, using the population internal z-score as standard. The analysis was stratified by sex, and multinomial logistic regression was used in crude and adjusted analyses.

Results: A total of 1963 men and 1739 women were analyzed. The mean age of the participants in 2004-5 was 22.7 years. Of the participants exhibiting increased BMI z-scores, 17% perceived themselves as thinner than ideal, whereas 48% perceived themselves as fatter than ideal. The prevalence of dissatisfaction was higher in women because they perceived themselves as fatter than ideal on the three categories of z-score change (≥ + 0.5 sd; -0.49 to + 0.49 sd and ≤ -0.5 sd); 81% of women exhibiting an increased BMI z-score reported dissatisfaction. The analysis adjusted for confounding factors revealed that women with increased BMI z-scores were less prone to feel thinner than ideal. Additionally, the increased risk of dissatisfaction due to perceiving oneself as fatter than ideal was similar between men and women (RRR = 3.52 95% CI: 2.17 to 4.56 and RRR = 4.08 95% CI: 3.00 to 5.56, respectively) using -0.49 to +0.49 sd as the reference category.

Conclusions: Individuals exhibiting increased BMI z-scores between 4 and 23 years of age reported higher risks of body dissatisfaction at 23 years of age. This finding is important because body dissatisfaction can cause psychological, social, self-esteem problems, and well-being.