Thoughts on calories and metabolism function?

If you think 1200 is too low, set your goal to something other than two pounds per week.

Your metabolism almost certainly isn't messed up.

A TDEE calculator can help you figure out your rough caloris needs. http://tdeecalculator.net/ Most people go with sedentary numbers and then add the exercise into MFP seperately as they do it.

A pound of weight lost requires a caloric deficit of about 3500 calories. If you want to lose 1 lb per week, that works out to a deficit of about 500 calories per day.

You are not small, so I am guessing you could raise your calories. I am 5'8" and was eating about 1500 calories per day (give or take 500 calories) and losing 2 lbs per week for a few months. I am now at a normal BMI and my TDEE is about 1600, but I am stll losing close to a pound per week, without exercise.

BTW, I'm a celiac too. Have you been tested yet? It's often a good idea to get tested before going GF because the tests require that you are eating gluten in the 2-3 months prior to testing. Going back to gluten for an entire season often isn't a pleasant experience.

Best wishes.

1200 is your base and you will earning more through exercise.

When you say "I lose so slow", what do you mean? (I ask because sometimes the silly weight-loss TV shows and magazine articles have skewed people's ideas of what normal weight loss is or should be.)

At 171, I'd infer that you don't have a huge amount to lose - your BMI would be in the overweight range, not the obese range. So probably a pound a week, or even half a pound a week, would be a reasonable, sustainable & healthy goal. You could go for 2 pounds a week for a while (first 20 pounds or so), but I wouldn't suggest that if you start to feel fatigued or otherwise poorly, and it would be healthful to drop the rate of loss as you get closer to goal.

Background for my saying this: I'm 5'5, SW 183 (just a bit more than you) in April 2015, CW 136, heading for 125-130. I started out losing 2 pounds/week when I was heavier, but have gradually upped my calories to try to coast into maintenance. I'm now losing 0.5-1 pound a week (trying for 0.5) with a 1500 net calorie goal, and I eat back most of my (conservatively estimated) exercise calories (usually 300-some additional calories daily). I do weigh my food very carefully & log conscientiously. Oh, and I'm also 59 years old, and hypothyroid.

If you weigh and log carefully for a few weeks at a sustainable calorie goal, you can get a clear understanding of how much you lose (or gain) at that level, and can adjust accordingly.

I admit I'm still losing on more calories than MFP thinks it would take at my age. I used to think I had a slow metabolism. Now I'm pretty sure I was just eating to (substantial) excess.