Maybe. 1# of muscle only contains ~500 Cal(vs. 3,500Cal for a # of fat), so a pretty small surplus could result in a significant weight gain. Water retention can also cause a sudden increase in your weight.

How tall are you? 133# would be near optimal if you are a little over average height, or if you are muscular.

If you are gaining fat or muscle you certainly are NOT in starvation mode.

I would doubt that the weight gain is muscle if your only exercise is running at 6 mph for 1/2 hour 3-4 times a week. That's not a muscle gaining exercise. If you are SURE that your calories haven't changed (are you tracking carefully?), has anything else? Did you just start taking birth control pills, athsma medications, anti-depressants, or are you having any odd symtoms like cold, fatigue, brittle nails, etc?

Mel

Have you gained height?

Dunno if this is related, but a few days ago I was watching a show about a family of dwarfs (the Foos family) on Discovery Health (quite interesting BTW!) and in one part, they were filming the mom going grocery shopping and she mentioned how she needs to lose weight but to do so she would have to drop her calories to around 800 per day, which she's not quite ready to do. (if you haven't seen this show, check the Discovery Health listings...they might show it again some time!)

Just thought that was interesting...

growth spurt ?
 

Is it at all possible you've hit a growth spurt ? That would make you weigh more without changing in size. I grew 2 inches somewhere between 15 and 21 despite horrible eating habbits. I wish I'd given my body better nutrition so I was taller.

I'm pretty sure a teenager's body works differently from those of us who are all grown. I remember reading that the generation after ww2 in Europe was markedly shorter than previous ones. Like losing your period, stopping growth is an easy way for the body to respond and will definitely decrease the number of calories your body needs to maintain.

I really don't mean to be patronizing, but at your age, at your weight, you should not be on a weight loss diet without medical supervision. Go see your doctor, ask his/her advice. You are always free to ignore it, but it may get you thinking.

kat.
(just dropping in)

I concur with the above comments, equinekrazed--you are in your growth years. Unless you're currently at or under 5' 1" in height, you're doing fine (your BMI would be 25 or under---in other words, normal range). If anything, you probably need more than 1,200 calories to support healthy growth of your tissues (as well as regular exercise, of course--but you're doing that anyways.)

Not getting enough calories/nutrients can stunt your growth and have other undesirable effects (e.g. irregular periods, brittle hair, etc.)

Of course, now is also a good time to develop healthy eating habits. When consuming those "extra calories" - opt for healthier options (and be sure to get that calcium for bone growth,) but give yourself slack to cheat whenever needed so you don't go on a binge-fest.

And if you still want to do a low-calorie-diet (below 1,500) be sure to consult with your doctor first.

Bump ... cuz people were askin'

featherz,

how did you go about increasing your calories from the weight loss level of 1500 to a higher maintenance level? I would guess you would have to be creative in creeping them up slowly in order to not gain wait, is that right?

I had a large free day once a week (probably 3K calories) and I stairstepped up my calories (one day 1500, next 1800, etc). I haven't gained any weight - although with the exercise I do I think I was vastly undereating at 1500 cals. I still was losing weight at 1800 so had to go up to 2100-2200.