Why am I gaining weight?

[Julie14401]

I am 19 years old, 5' 1, and my starting weight was 105 pounds. I know this is a healthy weight but I would still like to lose a few pounds of excess body fat and just tone up. I started dieting 3 weeks ago. For the 1st two weeks I ate around 900 calories per day and exercised for an hour per day. Over the course of 10 days my weight went down to 101 pounds. 4 days later though, at the 2 week mark, my weight shot up to 103 pounds without me changing my calorie consumption or workout regime. I read online that if you eat too few calories your metabolism slowing down causing weight loss to cease. After learning this I decided to up my calories to 1350 per day. This number is about 400 below what my maintenance calories should be. For the past week I have been eating 1350 calories per day and continuing to work out for an hour per day (cardio and weight lifting). I weighed myself this morning and the scale read 105.5 pounds! So, what is going on!? I should be losing weight but instead I am steadily gaining. I am so confused about what is happening right now and I am beyond frustrated.

By the way, I highly doubt my weight gain is due to increased muscle mass. It takes females a lot longer than a few weeks to gain enough muscle to account for weight gain especially while on a calorie deficit.

I would appreciate any insightful tips. Thank you for reading.

[Barb135]

You might also want to have your thyroid tested, since hypothyroidism can cause sudden weight gain and inability to lose.  A few years ago, I was sitting at 110 and within 3 months, I'd gained 30 pounds....... hypothyroidism.  I'm still struggling to lose it, in spite of diet, exercise.

[ducky406]

Not much of a help but I suggest, since what you want to do is tone up more than drop weight, you use measurements. I agree that a couple weeks is probably not enough to gain any significant muscle mass- but overtime, your measurements should change more than your weight.

Besides that- can you rule out pregnancy and PMS bloating? This is the third month in a row that PMS has caused me to gain almost a full kilo (2.2 lbs) in a week. If you bloat like I do, perhaps that's some of the weight.