Lauren is just 21. She's tall, lean, a college athlete. At that age, with that physique and activity level, her metabolism must race at a thousand miles per hour. It's easy for me to believe she suffered more than the others in her tribe, who were older. I know when I was 21 (also lean and a college athlete) if I didn't eat three big meals a day I was a very unhappy camper. This is one big advantage older folks have on Survivor: they can handle the food privation better than the youngsters.
As for the ones on EoE, I'm not sure they were getting less food than Lauren's tribe. Actually, with Chris' fishing, the EoE'ers might have eaten more. Also, they didn't have to take part in immunity and reward challenges.
It's easy to say other food sources exist out there But getting that food requires a skill set few have. That is why so many people lose so many pounds on Survivor.