system
Given the following post, respond as if you're commenting on Reddit:
human
How much of an impact does body weight have on lifespan?

I would guess that more body weight, regardless of muscle or fat, leads to a shorter lifespan since the more body mass you have, the harder your internal organs have to work, wearing them out faster, but I'm not completely sure.

Edit: I am referring to human body weight, but studies on other organisms are ok too.

Edit 2: Interesting answers here. I didn't take into account that more cells in the body might also mean an increased risk for one of them to become cancerous, but it can be different for other species. I guess at least for humans shorter people have a possible comeback against taller people now haha.
gpt
If you live in the UK or US, weighing 1/3rd more than your optimal body weight results in a lifespan which is 3 years shorter. 

But things really aren't straight forward, and there's a lot of other factors such as adaptability and routine which are very common in those aged 100 or older. But on average people who are normal weight live longer than those who are overweight. 

And living to great ages doesn't really happen simply because you're healthy, you also have to be happy. When researchers looked at those aged 100 or older they found plenty of daily routines such as a daily shot of whiskey, daily Dr Pepper, daily ice cream and daily bacon. But it is important to avoid excess.