Body fat and adipose tissue are considered to have beneficial effects
when they promote or protect the present and future function. These ef
fects do not occur at absolute amounts or percentages of the body weig
ht but rather they are context specific. Body fat stores are the major
energy stores of the body and are important determinants of survival
in starvation or undernutrition. Reproduction features highly as a bio
logical function. Humans are alone in having major sex-specific fat st
ores and patterns of fat distribution(1) and these have been linked wi
th the onset and maintenance of menstruation, with mate selection and
sexual signalling, and with favourable pregnancy and lactation outcome
s. To survive and reproduce good physical and psychological health are
advantageous attributes. Work metabolism, bone health and, possibly i
mmune function and energy balance itself, are related in functionally
beneficial ways to fat content and distribution.