There are four weight class break-points for equip load. Under 30%, 30% to 70%, 70% to 100%, and Over 100%.
Under 30% Allows the player character to fast roll a slightly longer distance than the below categories, but possesses no Poise health to prevent staggering if caught during recovery. Normal movement speed is not affected in this category.
30% to 70% Allows the player to fast roll but slightly less distance than Under 30%, but makes up for this by granting the player 15 Poise health so that they have a chance to continue their roll if hit by small weapons during recovery. Normal movement speed is not affected in this category.
70% to 100% Forces the player to slow or "fat" roll with less invincibility frames and a shorter roll distance than the previous two weight classes, as well as significantly more recovery frames. Under these conditions, the player is granted 30 Poise health which further improves the odds of completing the roll. Normal movement speed is not affected in this category. The player also incurs a -9 penalty to stamina regeneration.
Over 100% Does not allow the player to roll at all, and forces the player to "slow walk" (they are unable to run or sprint). An additional -5 penalty to stamina regeneration is added, resulting in a total penalty of -14 points/sec.
As is with every other stat in the game, it also has indirect bonuses such as increasing the player character's flat damage absorption. In particular, Vitality increases the player's flat defenses in the physical categories, making them more resistant against weapon damage.