I inject estradiol valerate and found my appetite increased significantly pretty much immediately. I gained 15 - 20 lbs over 6 months, and now I’m back to the weight I was before I started transition.
Considering you are underweight, don’t underestimate the importance of fat in feminizing a figure. Even if just temporarily it might be good to see this as a time where you intentionally want to put on extra weight (assuming you are suppressing testosterone and maintaining estrogen dominance), because that will help develop breast growth (which are fat stores), and hips and butt (which are also fat stores). Even fat in the face seems to play a big role in feminizing it.
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