The two authors share a near identical body-mass index(BMi), but as dual X-ray absorptiometry imagery shows that is where the similarity ends. The second author(figure, right) has substantially more body fat than the first author(figure, left). Lifestyle may be relevant: the first author runs marathons whereas the second author s main exercise Is running to beat the closing doors of the elevator in the hospital every morning. The contribution of genes to such adiposity is yet to be determined, although the possible relevance of intrauterine under-nutrition is supported by the second author's low birthweight The image is a useful reminder of the limitations of BMI as a measure of adiposity across populationsThe two authors share a near identical body-mass index (BMI), but as dual X-ray absorptiometry imagery shows that is where the similarity ends. The second author (figure, right) has substantially more body fat than the first author (figure, left). Lifestyle may be relevant: the first author runs marathons whereas the second author's main exercise is running to beat the closing doors of the elevator in the hospital every morning. The contribution of genes to such adiposity is yet to be determined, although the possible relevance of intrauterine under-nutrition is supported by the second author's low birthweight. The image is a useful reminder of the limitations of BMI as a measure of adiposity across populations