Maybe it gives so much for force, the speed at which they punch + the power of the hit makes them able to punch trough metal with ease, with no repercution
I have no idea how they resist hits tho, maybe an oversight?
fat acts as armor

and nice warming coat in winter
I like to think it just increases their metabolism and their fists would regenerate faster than sny pain they were to feel
And all that strength costs a huge appetite
Think about it, obenix is constantly super strong and therefore needs five boars a meal
It's a good thing they didn't try to drink an entire cauldron of magic potion then
Imagine how much food they'd consume
Asterix doesnt become strong so much, but he can easly eat a whole boar himself
That's pretty much how some wild animals survive winter, right?
He's just like all my family members
obelix will die in the end from heart attack due to the fact that he consumes so much meat
lot of meat is not healthy at all