system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Athletes that throw spears are fit, while those that throw neck-boulders are more of the bulky type. Why so?
gpt
Bulky is not the same thing as 'not fit.' Strength takes muscle, and more muscle can take up more space. This can lead to an appearance in very strong athletes that we may erroneously consider 'fat' or something along those lines. Part of this confusion arises due to body builders, who workout in ways to emphasize a specific muscle form that is, at least in part, tailored to appearance over raw strength. And so some people get the idea that is how a 'muscleman' looks. 

But if you look at strongman contests and the like, where strength is a more important end goal than appearance, you often see 'bulkier' contenders.

Beyond that, achieving and maintaining muscle takes a lot of energy, which means a lot of food. This can contribute to the overall bulky appearance, and cutting weight would reduce the dividends in strength as well. It's hard to build muscle while cutting weight, and can even be hard to maintain it.  

And finally, even if you don't have all that much fat, if you have a ton of muscle under it, it can contribute to a fattened appearance.