Calorie Cycling?

OP, many people here look at their calorie goal weekly rather than daily, so they have more cals some days and less others and it all comes out even over the week. However, having very high days and very low days can keep some people in a constant cycle of low-level binge/restrict that messes with their hunger cues and state of mind. Considering your past, it might not be a bad idea to try to even out that pattern a little, but ultimately you have to find what works for you. Have you talked to a doctor about your weight and eating?

It's great that you are no longer under-eating, but it's still concerning that you are underweight and "afraid to gain". Especially at your age, you could still be developing which can certainly affect your weight. Please continue to take care of yourself :flowerforyou: And please know I am only commenting out of concern.

Hello @hannalunaa!

I am glad that you're taking steps to improve your health.

Regretfully I will challenge you in your eating and maintenance assumptions as they are designed around absolute minimums, fall slightly below them at times, and by your own description are defended with "religious" fervour well beyond what would be viewed as common/normal (most people do not normally eat only 600 Cal to make up for being over 1000Cal the previous day)

You are currently at 17.8 BMI which still makes you officially under-weight.

It is normal for weight to fluctuate, so defending that low level of weight seems... excessive. You also make no mention of any strength or other goals other than maintaining a very low weight.

At 109lbs age 18 5ft 6" your BMR is 1291 and your choice of 1549 calories is slightly below the 1.25 sedentary multiplier MFP would give you. In fact it seems to be in line with a 1.2 activity multiplier you would get off a different calculator for sedentary and no exercise.

So your target calories are those that would be suitable for an extremely sedentary person, yet your lifestyle description is NOT.

You have a lifetime ahead of you and life will be a LOT easier for you in the future if you take the time now to sort through any issues you may be having that are not letting you enjoy a more normal relationship with food.

So while your calorie "cycling" as described will, of course, work, I disagree that the low caloric target and the defense of your current low weight are appropriate, and would challenge you to discuss both your target and how you view a potential weight gain to BMI 20 (frequently suggested as a minimal BMI for someone in recovery) with by preference with someone who specialises in helping out people with eating disorders and at an absolute minimum with your doctor.

As @kimny72 suggested, with a history of under-eating and your current age it would be far from impossible for you to actually still be developing and growing which would most certainly impact your weight. You don't sound like someone who would be able to handle that scale at this point of time and based on your post.