[xpantsx]

Baby powder and vaseline saved my life even before I took up running. I used to get very bad chaffing on the inner thighs even from martial arts training ( espec. when wearing a cup).
Keep it dry, keep it smooth. Parts of your body will rub, you cant help that and yyou dont want to change your body shape just to accomodate running. Im not sure from your post iif by losing weight from your legs you mean muscle or fat, if its fat sure youw ant to lose it but I guess that why you are running anyway ( see above though - you cant spot lose fat) ..if its muscle then are you wanting scarifice that? Maybe your build doesnt suit your style or youre a weight class above where you want to be but thats a whole different question to worrying about rubbing.
You could also look at your gear here. A pair of tight undershorts (possibly compression gear) of a flexible smooth material ( general rule of thumb .. more you pay the better it is) could help, that way its the material thats rubbing against material and this is not moving against the flesh with a rough surface. Grappling trunks should be fine too, if you can wrestle in them for 2 hours you should be fine to run in them for 40 minutes.
If youre getting rubbing on your feet, or as the above artcle says nipples ..the worst, i'd recomend applying some surgical tap over the affected areas prior to setting off. Even the thin layer makes a massive difference in protection.
When I run serious distance nowI always apply foot powder, vaseline, tape on the feet with a thin undersock and a thicker (but not thick) morino wool sock (sounds hot but its very cushioning and breathable ...expensive but the best sock material bar none for keeping your foot dry and happy). Powder my whole body ( to dry it off) and vaseline the inner thigh, butt crack and armpits and tape the nipples. Not even crossed my mind how gay this is.
I've gone from bleeding horror after a my first 10k run a few years ago to completing a 100km hill race this year without any open sores devloping or even serious blisters. Hurt in every other way conceivable and I would in no way condone or encourage this type of behaviour, but at least I got the bleeding thighs sorted.