At an equivalent skills level, obese women are less often employed than those who are not (7 points less likely to have a job). Conversely, among men, a higher body mass index is associated with a slightly higher probability of having a job. The wages of obese men and women are no different to those of non-obese individuals throughout the wage scale, but a higher body mass index is linked to a very slight drop in women's wages (-0.3%). This weaker performance of obese women in the labour market may at the same time reflect lower productivity, suspected or actually experienced discrimination, different preferences from non-obese women which influence employment, wages and body size by the same token and finally a simultaneous link between body size and employment or wage. Here we used data from the two waves of the Health and professional career survey (2006 and 2010). Based on the fact that in the past the regular practice of a physical activity reduced body size with no direct impact on employment or wage, we identified a causal effect of body size on employment which is more negative for women and null for men. The causal impacts of obesity and body size on hourly wages were also negative but the scales of impact were not always quantifiable due to the instrument's lack of power. These results were confirmed when we used the relative difference in body size compared to average body size in a reference group, rather than body mass index.