Figure 4. Effects of DR on survivorship of white rats in early laboratory studies from McCay and colleagues.

Survivorship curves were generated based upon experiments reported by McCay et al. (1935; 1939). Grey regions in (A) – (D) outline the survival curve of AL-fed rats, while the solid line represents the survival curve of DR-fed rats. Dotted lines denote one standard error above and below the estimated survival curve of DR-fed rats. P-values shown in (A) – (D) were generated from a log-rank test of the difference between the AL-fed and DR-fed survival curves. (A) Female rats were restricted in caloric intake at the time of weaning (n = 23 DR-fed; n = 22 AL-fed). At 25 months of age (arrow), half of the restricted rats were placed on the control diet, while the other half remained on the restricted diet. (B) Female rats were restricted in caloric intake two weeks after weaning (n = 19 DR-fed; n = 22 AL-fed). At 25 months of age (arrow), half of the restricted rats were placed on the control diet, while the other half remained on the restricted diet. (C) Male rats were provided a DR diet starting at an early age and maintained on this diet for at least 10 months (n = 35 DR-fed; n = 17 AL-fed). Prior to 10 months of age (arrow), temperature declines in the laboratory caused deaths in approximately half of the DR-fed rats. (D) Female rats were provided a DR diet starting at an early age and maintained on this diet for at least 10 months (n = 37 DR-fed; n = 17 AL-fed). Prior to 10 months of age (arrow), temperature declines in the laboratory caused deaths in approximately half of the DR-fed rats.