How Do Our Bodies Know When We Want To Lose???

I am currently in weight loss mode.  21 year old female 5'9".  Started at my biggest ever, 180, trying to get down to the 140s.  So far I have lost 20 lbs since Thanksgiving which is great.

My typical day is either, eat 1200-1300 calories and don't excersize, or exercize and eat back what I burned.  I've hit pleateaus before and broken them successfully over time.

However, I new question is realy bugging me.  This morning I was hoping to finaly be 159 after 2 days of 160, but nope, 160 again.  Yesterday I ate probably closer to 1300-1400.  What I don't understand is, how do our bodies distinguish eating for weight loss and maintenance?? When I eventually do get to my goal and start eating 1800-2000 calories like a normal person is my body going to freak out and gain weight like crazy?  Or can we never eat that much again?

I am so puzzled by this and would appreciate any input!

Thanks CC

Nicki

I've been wondering that too.

My plan was to slowly increase calories when I reached my goal. Each week, I'd add about 75-100 calories until I hit my "proper" calorie intake.

I'm not sure if this is "legitimate" though.

(edit: Added last sentence)

Unless you're starving yourself as your diet, you won't suddenly gain a ton of weight on maintenance calories.  In fact, you might even lose a pound or two.  When I upped my calories to maintenance level (which I did not do gradually; one day I was eating 1500/day; the next day I was eating 2000), I found that I actually continued to lose weight - albeit slowly - until my body finds a 'happy weight'.

The only way your body really distinguishes between weight loss and maintenance is in whether or not it needs to turn to fat reserves because you didn't feed it enough.  This will be partly determined by your hormones.  If you need to do something and don't have enough readily available energy to do it, your body will produce hormones that signal "time to burn fat!"  Just like if there are extra calories, your body will produce different hormones that signal "time to store fat!"  When you're in maintenance, those won't happen as much and will balance each other out.

One thing I should note, though, is that exercise/activity is an important part of weight maintenance.  If you truly are totally sedentary, you probably won't be able to eat 2000 cals/day.  That's for women who are at least lightly active.  This calculator: http://www.phord.com/cc/ suggests that if you are sedentary at 140 pounds, you will only burn 1760 calories/day.  Increase your activity to 'lightly active' and you increase your daily burn to just over 2000.