In some cultures, and historically in Western cultures, being fat was a sign of wealth. You could afford to overeat. Similarly, 150 years ago and more, having pale skin was considered beautiful, tans were for peasants. Then with industrialization, the "peasants" worked inside in factories and were pale, and those with leisure could take in the sun - so being tan was beautiful, and pale was "pasty" and unattractive.
Now the ball swings the other way - ozone holes make tanning risky, so pale is coming back in, and only the wealthy have the time and money to go to the gym, while everyone else eats processed food and watches a few hours of TV before crashing out - so thin is back in here in the industrialized world...
In some cultures, fat is still where it's at.