It's supposed to mean "Don't worry about stuff to a point that it becomes mentally unhealthy." It does not mean "Health is not important." But obviously the HAES crowds used the same slogans to fake EDs and tell themselves being obese is okay.  The irony for fats is that bulimia is statistically more common than anorexia, as is compulsive overeating.  EDs that make you eat too much are more common than their stereotype of "ED = thin."