For the calories we take your 125lb goal and convert it to kg and we get 56kg...So that means 56g of protien, 28g of carb, and 112g of fat (if you are trying to lose weight).
So we can multiply the 56 x 4 = 224, the 28 x 4 = 112, and the 112 x 9 = 1008, then add them together to get 1344 and that is your calorie goal.
I am 5'7" and I could not get to 125 if they cut off one of my legs! 150 is the lowest I have weighed since I have gotten to that height, and I wore a size 5 (that is a 30 years ago size 5 not current) and I looked skeletal. So that is where I was coming from.