It depends where you buy and what you buy. The poor in developing countries, ironically, get lots of vegetables and can be pretty fit (compared to ours at least). People don't really get fat because they eat too much meat (they can, just not common); its more the sugary and starchy processed foods that do it...and those sell like crack in the developed world.

Of course, one could always hit the gym...if they have enough money (or just move to California and ride a bike everywhere...if they have enough money).