Response to Janiszewski et al.

Abstract

We thank Dr Janiszewski and Dr Kuk for their thoughtful comments.1 These comments highlight the complexity of the relationships between different fat depots and metabolic health. The protective effects of the gluteofemoral fat depot are independent of other body fat depots. However, in any cross-sectional study there are strong positive correlations between gluteofemoral fat mass and total and abdominal fat mass. For instance, in our own cohort of 1500 randomly selected healthy individuals, waist circumference is significantly correlated to hip circumference (r=0.79 in women, r=0.82 in men, P<0.001). Hence, the protective effects of gluteofemoral fat are only seen after appropriate statistical adjustment for other fat depots. In obese individuals, the deleterious effects of their increased waist circumference may override any protection that the gluteofemoral fat depot provides. Weight loss, as studied by Janiszewski et al.,1 results in the reduction of total fat mass, abdominal fat mass and, concomitantly, gluteofemoral fat mass. Thus, physiological gluteofemoral fat loss through diet and exercise is closely linked to the decrease in abdominal fat mass and its associated beneficial effects, and indeed in their study reductions in lower-body subcutaneous fat were not related to metabolic health improvements after adjustment for changes in other fat depots. In contrast, the isolated gluteofemoral fat mass loss observed in diseases like Cushing's syndrome and lipodystrophy is clearly associated with deleterious metabolic effects.