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It's very unlikely that it's impossible, but you may want to remove "human" from the title, if you want to make it plausible.

There are many large animals that are 15-18 feet tall and they go on to live pretty long lives. However, the energy required to operate those bodies along with the human intellect will definitely take a toll on lifespan, unless you revamp the structure of the human body.

Blade Runner(1982) has a good explanation for this.

 > **Tyrell:** The light that burns twice as bright burns half as long, and you have burned so very very brightly Roy.

The replicants in the movie are basically powerful augmented humans that can accomplish insane feats of power and intelligence, but their lifespan is shortened to 4 years, due to the speed of aging and deterioration.