One could posit a possible "optimum wealth level". Where most people don't have money for prepared high-fat foods, but *do* have money for decent nutrition. Below that, life expectancy decreases because they're not getting adequate nutrition, above it, life expectancy decreases due to unhealthy levels of fat and the attendant heart disease etcetera. But then there's the complicating factor of healthcare, which partially offsets the reductions due to wealth.