Little Johnny is sitting on a …

Little Johnny is sitting on a park bench scoffing his face on a big bag of sweets. An old man comes over to him and begins to stare at him.
“What?” Johnny says,
“Those will rot your teeth and give you bad health in later life.” the old man replies.
“Well my granddad ate sweets all his life and he lived to 95!” Johnny says.
“95! how?” the old man replies.
“By keeping his fucking mouth shut….”