It's the pretty visible 'V' shape in the shadow where the legs connect that gives the impression that the character looks fat. I really don't think its that noticeable though, and it doesn't really make the template look fat as a whole to myself.
I'm not an expert on this stuff, so maybe someone more experienced will tell you differently. However, right now I think the biggest issues here are your color palette choice and torso movement. I was looking at your palette and noticed that when you changed colors there was no variation in hue, you only changed saturation and brightness. When you go to darker colors for skin, you generaly want to incorporate some more red into it.
Here's a quick palette swap to show you, again I'm not an expert at this so I'm sure it's not perfect. Even if you are wanting to make your base template a non-white color, You're still going to have to play around with the palette you currently have.
The other issue I see with your template right now is that the body's torso does not seem to move as a whole with the arms and legs movement. For the most part it appears to only move up and down as the character moves, and doesn't move with the arms/legs as much as it needs to. I can't provide a good example for how to fix this, maybe someone else can. It might be something you can fix by just messing around with your shading a bit more. (yes, I was looking at the new sprite animated)
