I find the second part of that statement in need of some “Show me the science.”
I cannot find a link to suggest that non-military Russians were healthier during WW2 than immediately before or after. Mortality during the war was considerably higher, but it’s hard to disentangle the health of the general citizenship from the casualties of the front line, as the Nazis were are the backdoor and in control of large plots of Russian food producing land.
I am very skeptical of your statement that folks were healthier in that period.