I know BMI is not the end all and be all, but it has become the basic guideline and it actually cuts a fairly wide berth. For 5'4", anything from 108 to 145 is in the normal range according to US National Institutes of Health. It is going to depend on your age, body type, bone structure, muscle tone etc. People feel better on different ends of the range. Some feel weak on the low end, some feel sluggish or bulky on the high end.
mag- ITA with everything you have said. Elimination of whole food groups, feeling weak or nauseated, fasting, these are all things that cannot be sustained and will not get anyone on a regular long term healthy path. Weight loss equals calorie intake and there is no fasting diet that will allow anyone to go back to "regular" eating without gaining some weight back if regular means that you intake more than you burn. And I don't know how you can get exercise if you have no energy before 10 am or after 6 pm.
Any kind of refresh or cleanse should be limited in duration. I sometimes do a refresh that involves vegan high protein shakes, plenty of veggies, fruits, water, green tea or herb tea. Not starving! 3 days takes off 5-9 lbs (I am tall and large boned, still on the high end of the overweight BMI -- but down from Obese 2!). I get rid a lot of retained fluid and bloat from no dairy or heavy carbs. On day 4, I gain back 3 when I start eating salt, dairy, carbs. But its ok, it is just designed for post vacation bloat, get me off alcohol and sugar, get me started on the balanced path after holidays or vacation overeating.
I also subscribe to the notion that some foods just don't work for some people. I know the recommendation is that if you are going to eat carbs, eat whole grains, brown rice, wheat pasta etc. I have never been diagnosed as celiac, but whole grains, quinoa, things like tempeh, wheat will make me feel bloated, mild stomach ache, skin rash, and mild asthma. Not like I am sick to my stomach, but just not my friend! If I eat bread, it is going to be sourdough, and I feel just fine. Most non fructose sugar=headache and drop in energy. If you pair down your food, then add back, you can learn a lot about what makes you individually feel good or bad.