Facial shape is a reliable correlate of body mass index (BMI) and facial correlates of weight predict both actual and perceived health. Previous studies have found that facial shape cues to weight are strongly related to attractiveness independent of other components of attractiveness, such as skin colour, skin texture and age. In a recent study, facial weight (or facial adiposity) of male faces was found to provide a stronger link between attractiveness and immunocompetence than facial masculinity-femininity, which is often considered a fundamental aspect of beauty. This study examined the perceptual thresholds for a noticeable change in facial weight (represented in BMI values) in three-dimensional faces. Thresholds of 1.3 kg/m2 were found in men’s faces and 1.6 kg/m2 in women’s faces. These values represent relatively minor changes in BMI indicating that relatively subtle changes in facial weight alter facial appearance. Furthermore, thresholds were lower in men’s faces than women’s, suggesting that facial cues to weight differ between men and women. It is proposed that it might be more appropriate to refer to facial weight instead of facial adiposity, as it is not necessarily only adipose tissue that drives the perception of weight. Combined with previous findings linking facial weight, health and attractiveness, these results might help to design appearance-based interventional studies which can be an incentive for the maintenance of a healthy ideal weight.