It’s a shame that none of the publically available sliders are good. Coldsteel’s are better than the rest, but they don’t look fat so much as inflated and only one set of sliders affects hands and feet. Fortunately, you can port sliders from Fallout 4 (though it’s not all that simple) and it’s not hard to touch them up in Bodyslide and Outfit Studio, as I’ve done here.
You can make the face and neck gradually get fatter with the rest of the body, but it works only if the actual weight is changed, so, not many mods will affect it (I think SexLab Hormones does, but not WeightMorphs since the latter affects morphs and not weight). In order to do that, you need to modify SkinnyMorph slider the head’s .tri file has though unlike others, it needs to be done in reverse (at 0, it should be fat and at 100, it should be skinny), so, it’s a little tricky.
Moreover, you can make animations change with higher weight throug DAR, but it’s not an automatic process, you need a variable to track real weight and it can be done only in a number of stages, i.e. you have to make animations for weight 0-10, 11-20, 21-30.
All of this is a lot of work, but it’s worth it. I also recommend using SMP physics for things like hair and capes since they actually conform fattening bodies as seen on the screenshot above (you can see how the cloth does a good job hiding breasts at weight 0, but fails to cover anything at weight 100 without stretching while hair moves properly over her butt instead of clipping into it).