Getting up to maintenance calories when in energy deprivation without gaining fat?

[LORD3PAPRIKA]

Hello! I am a 16 year old female, 54kg (119 lbs), 175cm (5'8").

I recently had an InBody scan that showed I have a percent body fat of 24.2% and pretty low levels of skeletal lean muscle (22.1kg = under normal). According to the test my BMR is 1257. The test suggests I gain 9.1kg of muscle, which I completely agree with, but how do I do this without gaining fat?

I have been in a caloric deficit for quite a while and am probably in an energy-deprived state as I haven't had my menstruation for roughly 3-4 months. I weigh and calculate my calories using Lifesum and often land at around 900-1100 calories a day. I'm afraid that if I start eating maintenance (how do I even know what my maintenance is?) I will gain the fat I lost.

I lift dumbbells at home three days a week and focus mostly on full body routines, but I'm not sure I'm doing a great job at it (aka not effective workouts). I am planning on starting lifting weights at a gym within this month (with proper guidance) but I know I won't have any results unless I eat properly first.

I already eat clean (lean protein, complex carbs most of the time, olive oil/avo/nuts for fats) and cook everything myself. I try to have as few "cheat days" as possible, but sometimes allow myself to have bad days (never more than once a week though)

Thankful for advice & help!!

[SuffolkPunch]

The fact that your period has stopped should be a giant warning sign. Don't starve yourself, it's not worth it. At your age, you should focus on building muscle. I would slowly increase calories and focus on progression with weight training.

Ignore numbers like muscle mass from BIA machines and BMI, these are of very little value due to inaccuracies and making assumptions about your body composition.

[SugarFree1]

Those biometric machines can be very inaccurate. A couple odd things that stick out to me is that in for your bodyfat to be lean enough to stop menstruation is definitely at much lower levels of bodyfat. The second is that by your bodyfat results of 24%, you would have around 28lbs fat - 90 lbs of Lean Body Mass. As far as upping calories to maintenance levels I would suggest looking up Reverse Dieting.