I think Litten3 is literally the only buff starter we got. Everyone else is either fat or lean.
I was going to try and counter that, but after thinking about it, you're totally right.
Blastoise- fat turtle
Venusaur- Fat....plant monster...thing
Charizard- Just a stereotypical western dragon, though in some art it does look like he's dangerously close to developing a beer-belly
Meganium- A brontosaurus...also kinda chunky
Feraligtor- a Bipedal alligator; pretty standard looking, no buff-ness to him
Typhlosion- Awesome incarnate, but not buff in any way
Swampert- Again, nothing buff about him...cant say he's sleek, but nobody would really say he looks muscly either
Sceptile- Nope; in fact, his arms are kinda scrawny
Blaziken- sleek design; looks lie a kick-boxer wearing some leg warmers, but even then his legs dont look jacked
Torterra- Quadruped with a forest growing on its back; we actually cant see much of his body outside his shell
Infernape- That monkey is very definitely not buff
Empoleon- Kinda chubby emporer penguin with flippers; I dont think its possible for him to look buff
Seviper- Doesnt even have appendages
Samurott- Reverted in its final form and became a quadruped covered in armor; he's not buff either
Emboar- Definitely fat. No hiding that one
Delphox- Slender fox in a robe
Chesknaught- Bulky...I dont even know what...in some armor
Greninja- sleek frog ninja
So...yeah, a buff cat wrestler...or really just a buff starter in general is pretty new. I mean, who else really has a buff physique beyond the Machamp line? The Nido pair maybe?