Skinfold thickness measures (with calipers), underwater weighing, bioelectrical impedance, dual-energy x-ray absorptiometry (DXA), and isotope dilution are some more ways for measuring body fatness. However, these procedures are not always readily available, and they are either expensive or need highly experienced staff to carry out. Furthermore, many of these procedures are difficult to standardize between observers or computers, making comparisons across research and time periods more challenging.