Big loss this week - should i be concerned?

nickyjl81

I've lost 18lbs over the last 3.5 months. At first I was losing 2-2.5lbs a week then i plateaued for 3 weeks and since then i've lost 1lb - 1.5lbs a week. I have had a mini plateau over the last week and a half with no loss but then this week I've lost about 4.5lbs. I know its not water weight because I drink loads of water (although I don't log it) so why would i get such a big number and is this ok?

I stick to around 1400 calories a day and eat back my exercise cals. I'm working out 4-5 times a week and burning around 450 cals per workout.

Should I up my calories a little? I've just worked out my BMR as 1530 and my TDEE is around 2300 (this was a bit of a shock!).

Thanks for any advice.