Non, du pain pour la vie
Why not du pain??
Unless referring to some specific bread, adverbs of quantity use "de" by itself here. So "mange moins de pain" would be understood as a general imperative to "eat less bread", not "eat less of the bread".
After visiting France and seeing all the popular bakeries, this phrase may be illegal to say over there, LOL. Mangez plus de pain! :-D
"de", not "du"?
Because it is moins de, whatever the noun after less. Also works with plus de. Je voudrais moins de travail/plus d'argent/plus de vacances/moins de problèmes...
Why not du pain?