From a Science Journal study (Feb 21, 2020):
We suggest this increase in mortality seen on DR in the 4-day switch treatment is due to either accrued physiological costs or more probable, a carryover of deaths directly resulting from the rich diet, but recorded on the DR diet.
A closer examination of the timing of mortality within the 4-day switching paradigm showed that the mortality response was strongest in the second 48 hours after exposure to both DR and rich diets.
Ageing has attracted extensive scientific interest, from both a fundamental and biomedical perspective. Dietary restriction (DR) extends health and life span across taxa, from baker’s yeast to mice, with very few exceptions (1, 2). The reduction in total calories—or restriction of macronutrients, such as protein—extends life span reliably (3–5). Although the precise universal mechanisms that connect DR to ageing remain elusive, translation of DR’s health benefits to human medicine is deemed possible. The widespread assumption of DR’s translational potential originates from the notion that DR’s beneficial effects are facilitated by shared evolutionary conserved mechanisms, as beneficial effects of DR are observed across taxa.