If a fat job applicant waddles into your office, should you assume he is lazy?
The MIDUS Study measured the body mass index (BMI) as well as personality characteristics of a large sample of adults. Here are the BMI/personality correlations for men and women:
Men (white, ages 40-59, n = 830)
Women (white, ages 40-59, n = 978)
The correlations are weak; they are a bit stronger for women. So there is a slight tendency for heavier people to be less achieving, less conscientious, and lacking in self-control, but no more than a slight tendency.