Response to: 'Is non-industrial society undergoing an energy balance transition predisposed to accumulate abdominal adipose tissue and susceptible to knee osteoarthritis?' by Yu et al

Many thanks to Yu and colleagues1 for their interest in our recent paper on knee osteoarthritis (OA) susceptibility among the Tarahumara, an indigenous population of subsistence farmers in Mexico undergoing rapid lifestyle changes that promote positive energy balance.2 We welcome their constructive comments and are happy to respond.\n\nAs Yu et al point out, a key prediction of the model we proposed for knee OA risk among non-industrial societies is that people born under conditions of limited energy availability are prone to accumulate and maintain excess abdominal adipose tissue if they later experience chronic positive energy balance.3 4 As a result, such people are vulnerable to developing a relatively low body mass index (BMI) but high abdominal adiposity,5 which we hypothesised puts them at greater risk of knee OA for a given BMI.\n\nYu et al do not disagree that the Tarahumara men we studied had significantly lower BMIs, on average, than the individuals in our comparative sample, urban American men from Framingham, Massachusetts. However, they question whether the Tarahumara had relatively larger abdomens and were prone to accumulating and maintaining abdominal adipose tissue. Average overall body size among the Tarahumara was much smaller than among Framingham individuals, which we needed to account for when comparing abdomen sizes between the two groups. In our paper, we showed that after controlling statistically for body weight and age, Tarahumara’s abdomen circumferences were significantly larger than …