While some authors have reported a correlation between BMI and negative or positive body image components, numerous other studies have highlighted a non-linear evolution of self-perceptions across BMI classes. As body dissatisfaction, appearance investment and body appreciation are linked to psychological health, the aim of this study was to determine whether they are also related to BMI among women and, if so, whether a BMI-defined classification would be useful for identifying thresholds in self-perceptions. Body dissatisfaction, appearance investment (including motivational salience and self-evaluative salience) and body appreciation were assessed using three validated scales in 505 women, aged 19 to 78. The women were then stratified into five BMI groups: healthy weight, overweight, obesity class I, II, and III. Discrepancies in body dissatisfaction, appearance investment and body appreciation were identified through a comparative analysis of BMI groups (ps < 0.01). The results showed that women with obesity have an altered negative and positive body image compared to those with a lower BMI. Some variables seem to plateau above a certain BMI threshold. This ‘tipping point’ occurs from overweight upwards in the case of body dissatisfaction and from class I obesity for body appreciation. Our results offer an insight into the value of BMI classes in defining levels of negative and positive body image and adapting care for women. From the very onset of overweight, the support offered should aim to restore body appreciation, limit dysfunctional appearance investment, and curb body dissatisfaction.