Hi, I'm on my soapbox.
Yesterday I noticed a few posters whose goal weights were very low for their heights. I punched in the BMIs and they were about 16.5.
I realize some people are naturally thin. Many models say they eat whatever they want and never exercise and are just naturally underweight. Fair enough. I've known people to be extremely slim without trying. I understand.
But I think the key word here is naturally. If you are 20 lbs overweight and you are trying to be 20 lbs underweight... that doesn't seem like your natural weight would be in the underweight category. My boyfriend is slightly underweight, eats more than me, very little exercise. If he put on a bunch of weight and needed to lose, why would he try to go back to his underweight weight? His metabolism has shifted so that he can no longer naturally maintain it.
Anyways, I have worked with people with eating disorders for a few years AND I've had an eating disorder myself. My goal weight up until recently was 99 lbs which is a BMI of 18.6 on the nose. Every person I've worked with an eating disorder had a goal weight well below the healthy level. They were never allowed to see how much they weighed which was lose-lose. If they saw their weight, they felt too fat and wouldn't eat. If they didn't see their weight, they assumed they were gaining and wouldn't eat. And many of them had been overweight too. It seemed that while they were overweight, they glamourized the thinnest people and figured out how to get there. To get to these unhealthy weights, you need A LOT of calorie reducing.. like consuming 500 calories or less a day.
I just think that for some of the posters with underweight goal weights--you'll reach a healthy weight and be unhappy and frustrated with how you look... THAT'S not healthy. In fact you'll spend the whole time you're at a healthy weight being unhappy and unsatisfied. That to me is disordered thinking.
So if your goal weight is below the healthy BMI... please reconsider. You'll spend a long time being dissatisfied with your body and your goal might be impossible to achieve or maybe only achievable through unhealthy means.