I've had that problem. I used to be significantly underweight, quite a few times in my life. My hormone levels are low, so I have to be on birth control to even things out. Now I have no problems gaining weight lol. I've tried to go off a few times, but I just can't.
2c-3a - med-coarse - normal-high porosity - high density

NP/LP: CJ Daily Fix, KMF Whenever / Giovanni TTTT
RO/LI: Sevi Pumpkin Seed, CJ Argan & Olive Oil, Aussie Moist, TN Nourishing Moisture, YTCucs
DC: KC Stellar Strands
STYLER: Ouidad Climate Control, KCCC, SS Curl Enhancing Jelly, JC Rockin' Ringlets
COLOR: henna, amla & indigo
: glycerin in high/low dews, polyquats, parabens