I thought I'd briefly compile stat changes made from altering the body sliders, namely weight. The game's H settings are normal (can't remove panties in R-15 mode), the standard sword is equipped and [remove all] is selected. Listed sliders are ones that made a weight difference. This is listed in order of minimum then max, with their differences versus the base weight. The standard weight is 52.6kg.
[Breast Adjustment]
Size: 52.1(-.5) 55.2(+2.6)
[Body Adjustment]
Arm Thickness: 52.4(-.2) 52.9 (+.3)
Stomach Protrusion: 52.4 (-.2) 53.0(+.4)
Leg Thickness: 52.1(-.5) 53.7(+1.1)
Buttock Size: 52.3(-.3) 52.9(+.3)
As shown, the slider increases more kg than it removes despite the slider's visual position, visual placement of the slider is deceptive and a change to make it more accurately placed would be nice. Base elemental resistance changes takes place as your kg hits minimum milestones. Bringing your weight below 52.6kg does nothing even at max reduction (-1.4). The base for all resistances is [Lowest] and move speed is [Very Fast]
53.8: All [Very Low] [Very Fast]
55.4: All [Very Low] [Fast]
57.6: All [Very Low] [Fast]
Not seen with the listed parameters is the hidden numeral strength of resistances; not all resistances are raised equally. For example, wearing standard gear (click reset) with max base weight provides:
68.1 kg: [Very High] [Quite High] [Low] [Quite High] [Quite Slow]
Versus standard:
63.1 kg: [High] [Medium] [Low] [Medium] [Quite Slow]
I'm not entirely sure what the resistances entail, fire is a DoT and ice slows you, they don't really do much in the early game as many enemies appear phys only.