An apple can be quite a satisfying meal.
Try to dispel what you picture as a ‘normal meal’ upon hearing that.
It’s all about the context.
I’m not talking about ‘if you were starving on a desert island’, which isn’t practical.
Rather, when it’s the best choice available based on your time & options, and if you chew it mindfully, then it is possible to be one of the satisfying meal you’ve ever had.