I'm not sure willpower is the right word to use here. If there was proof that a certain diet had a significant positive effect on increasing my lifespan, I would almost definitely pursue it. It would be irresponsible not to.
On the other hand, I think it would be irresponsible to pursue it based purely on the fact it lengthened your lifespan. For example, I personally would not pursue caloric restriction if it yielded a single year of life on average. Quality of life matters.
Are you at all overweight right now? (The majority of Americans are.) so, your claim is self-refuting.