Genetics works at a much more massive scale (numbers and time wise) unless there's the kind of trully exceptional circumstances where almost all individuals of a tribe perish without leaving any descendands (in which case only the genetical material of the survivours could possibly carry on forward), so most of it is to do with tiny differences in the probability to reproduce which over many generations and across millions of individuals cause a certain characteristic to become preponderant.

So a single generation (or two or three) going through starvation wouldn't do much to the genes themselves unless it was so extreme that the "only handlfull of survivors, no living descendents for the others" situation happenned (and even then it would only affect that tribe and might later dilute itself to non-existence through intermixing with other tribes)

Epigenetics on the other hand has to do with proteins that surround the genome but are not the DNA itself, which can toggle genes ON/OFF or influence their expression, which can change during an individual's life due to environmental factors and which can also be passed from parents to children. It seems to be a far more reactive mechanism but also one which is more temporary.

Whilst epigenetics also has to do with genes, it is something only recently discovered and in it the information is not stored in the DNA.