system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How does buffalos get so big while being herbivores?

I'm sorry for asking this. But I always wondered how come cows and buffaloes who only eat grass and stuff get so big? Here I am working out 5 days a week with my job and eating a lot of meat and getting normal results. Sorry again, I have no intention of annoying anyone.
gpt
Your entire day (whole life, really) revolves around eating. Yeah, grass is low in calories, but when you are basically chewing from the moment you wake up to the moment you go to sleep ,You can put down quite a few calories.

Also, there's only a couple of things that can eat them.