You know you're getting older when the first thing you do after you're done eating is look for a place to lie down.

In this joke, Anderson uses a familiar, bodily detail—post-meal fatigue—to mark the passage into older age. The humor comes from treating a small shift in routine (seeking a place to lie down after eating) as a definitive “you’re getting older” milestone. It plays on the contrast between youthful energy, when meals are fuel for activity, and later-life rhythms, when digestion and tiredness can dictate behavior. The line also gently normalizes aging by framing it as an everyday experience rather than a dramatic decline, inviting the audience to laugh in recognition at a shared, slightly embarrassing truth.