Here's a cite for First Nations vs. European ancestry. It doesn't say anything about availability of food, just a different distribution of body fat and hence higher levels of obesity, as it is measured.
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9822953&dopt=Abstract
I remember seeing somewhere (so this is not at all a credible statement, given my memory) that though folks indigenous to Greenland ate very high fat diets and were, by the standard definition, relatively overweight, they did not suffer as much from diseases that typically affect overweight folks of European ancestry.
Many grains of salt with that last paragraph, if not with the first.