When I was in ninth grade, I was a bit heavier than the average kid.
One day in class, I mentioned that I skipped dessert by the Shabbos meal since it was fattening and I truly didn’t need it.
My rebbi at the time spent the next ten minutes of class time berating me publicly for “dieting on Shabbos” and not having any respect for the concept of oneg on Shabbos. One does not diet on Shabbos, he told us firmly.
Mind you, I was not even on a formal diet. All I did was skip a piece of cake that I recognized wouldn’t help my weight. But that didn’t matter — for this terrible action, I was subject to public humiliation in front of the entire class.
Needless to say, my rebbi was dead wrong. There is nothing wrong with skipping a piece of cake on Shabbos.
The Wolf