I'm 5ft 7 and I weighed 12st 2lbs when I started Low Carbing. I didn't restrict calories, didn't even count them at all - just carbs. Neither did I intend getting down to 10st at my lightest - it just happened as a result of me losing between 1 .5 to 2lbs per week as a result of my Low Carb with higher Protein and 'natural traditional ' Fat.
Meaning I never ate 'fat bombs etc., but stopped seeking out Low Fat food - seeking Full Fat ones instead and stopped cutting the fat off bacon and other meats. I reckon that I actually ate more calories than before in the first few weeks due to replacing the carby foods with either Protein or traditional fat (such as hard cheese, nuts, full fat greek yogurt etc.).
When my weight dropped below 11st I started to have a little concern about when it would stop, but I was determined to 'beat' Type 2 and my BMI was still at the upper end of the 'healthy weight' ( 23.8 down from 26.6).
At my absolute lowest weight my BMI was 21.9 which is in the middle of the 'healthy weight' range for me. Since I got 'fat adapted' and got my HbA1C down below 42 I have allowed myself to snack on low carb foods and my weight has gone up to 10st 5lbs - so my current BMI is 22.7, but I'm a long way from being underweight because the low side of the 'healthy range' for me is way down at 8st 6lbs!