geriatric bypass:
1. The act of denying your actual age in order to give others the impression that you are younger.
2. A medical procedure intended to provide persons of advanced years the appearance of being younger.
For the last twenty years, Jack claimed to others that he's only 39 years of age, and for the last five, he's even used hair coloring. He acts as if he's had a geriatric bypass.
From urban dictionary.