"I also do it by talking about things they're better off than me. I'm fat and old and I'm going to die soon."
When host Alex Jones, 45, interrupted him to say "You are not!", Gervais laughed: "I am."
He admitted he had "brought down" the mood of the show, but he can't help but feel he's "closer to death" each morning.
But Gervais continued: "Every day I'm closer to death. Every day is a bigger percentage of the rest of your life and we don't know what percentage that will be 'If I die tomorrow, today was 50 per cent'."
Gervais has previously revealed his litany of health concerns in live videos from his London home during lockdown.
He said he drinks and eats too much, and was diagnosed as "pre-diabetic" – leaving him feeling like he was "pre-everything" in terms of life-threatening illnesses.
Gervais - who lives with his long-term partner Jane Fallon, 61 - added on The One Show he doesn't need the idea of an afterlife for comfort as he feels the natural world is supernatural enough.
Explaining the concept behind his new Netflix special SuperNature, he added: "I debunk the supernatural and conclude nature is super enough.
We don't need unicorns, we've got the octopus. It's nature, humanity, warts and all. The best and worst things about being alive."
Gervais has insisted his anti-woke jokes in the special are an example of "irony" after LGBT groups slammed them as "dangerous" and anti-trans.
He said: "In real life, of course I support trans rights. I support all human rights and trans rights are human rights."