Neither caloric nor protein restriction increases the male lifespan of outbred short-lived fish

Laboratory inbred strains respond strongly to dietary restriction (DR), whereas genetically diverse populations may not experience comparable benefits. The exceptionally short-lived fish, Nothobranchius furzeri, offers several genetically distinct captive populations; however, only the severely inbred GRZ strain has been tested for DR effects. Here, individually kept males (N = 111) of the outbred MZCS 222 strain of N. furzeri were assigned to 1/high-protein diet and two DR forms: 2/low-protein (isocaloric to high-protein but half the protein concentration), or 3/caloric-restriction (half the dose of HP at the feeding time). Neither form of DR significantly extended the lifespan of N. furzeri males. The limited efficacy of protein and caloric restriction in outbred N. furzeri may stem from insensitivity to these forms of DR or from the genetic diversity of the strain in comparison to earlier reported life extension through intermittent fasting in the inbred GRZ strain.