You are so fat that the waiter said to you every time: "Sorry for your weight" instead of "Sorry for the wait."
Sorry For Your Weight
Explanation
Explain Bear
Listen up, butterball! The joke is that you are so obese that the waiter confuses 'wait' with 'weight' because, well, your weight is probably the only thing on his mind when he sees you. It's a play on words, see? Bet you also thought 'exercise' was an extra 'size,' huh?