Explain 'EATING BACK' calories... ??

If you should net 1200 calories and you eat 1200 but burn 600 with exercise, you are netting only 600 calories which is probably not enough to met all your metabolic needs. You will then use body fat (good) and also muscle (bad) to supplement your metabolic needs. If you eat 1800 calories and burn 600, then you net 1200 and doesn't leave you r body with as wide of a deficit. I guess that is the way my simple mind understands it. You will probably also feel really hungry eating only 1200 calories and working out that hard.

There is divided opinion on the subject.

Those pro eating back your calories argue that eating back your calories can jump start weight loss, by getting your body used to the idea that fuel will be provided when you work hard.

Another camp thinks eating back your calories is a poor idea, arguing there is not much difference in day to day calorie needs even when you do exercise and it promotes the myth of calories in/calories out being the key thing. The big MFP myth.

My view. Protein is the key thing here. If I exercise, and I choose to eat back calories, I mainly only do it with protein. This helps muscle, without having a negative impact on your diet (the key contributor to weight loss).

A personal trainer is not a nutritionist.
If yours has you eating 1200 a day, then burning 400-600 calories, for a grand total of 600-800 calories net a day, he's an idiot. You can tell him i said so.

actually mathematically she's netting even less since 1200 calories was set up to already have her at a deficit

To maintain your weight right now, you would probably need to net 1700 or 1800 calories, so netting 1200 calories a day is set up to result in weight loss

A personal trainer is not a nutritionist.
If yours has you eating 1200 a day, then burning 400-600 calories, for a grand total of 600-800 calories net a day, he's an idiot. You can tell him i said so.

actually mathematically she's netting even less since 1200 calories was set up to already have her at a deficit

I don't understand what you mean by deficit when you say 1200 was already set up to have me at a deficit. Please forgive me, I'm just getting started and trying to do everything right.

We all burn calories all day long - sleeping, walking, brushing our teeth, folding laundry, work, exercise, etc (often referred to as a TDEE or total daily energy expenditure). Example, my TDEE is approximately 2200 cals a day, so in order to lose weight, I need to eat less than that - so if my daily calorie goal is less than 2200, I'm in a deficit and will lose weight.

That help?

1200 calories is considered to be the lowest recommended intake for women, but that's painting with a pretty broad brush since we're all different sizes, weights, heights, have varying activity levels, and of course different TDEEs. And as other have pointed out, your trainer is telling you to only eat that much regardless of activity, so that's taking an already low intake and making it even lower when you exercise and burn more calories, and leaves your body with very little fuel.

It's kinda like having taxes deducted automatically from your paycheck and then filing and using that money that was already taken to apply toward your tax bill for the year, versus not paying any taxes at all and having to come up with the money at the end of the year. Except when you don't eat back your calories it's like saying, "no I don't want any money taken out of my check" all year and then when your taxes are due saying, "ok just take that out of the money you collected from my check."

Actually it's not really like that but I just spent the weekend doing taxes and I can't stop thinking about it.

To lose fat you need to eat less than you've burned. This difference is called your calorie deficit. Most systems rely on you having an overall average of how much you burn with all daily activities including exercise and every last calorie you're expected to burn. Your deficit is an amount lower than that daily average. Note that some days where you are very inactive you might actually eat more than you burned, but on more active days your deficit is even higher.

(Personally I find this annoying because I get hungry when I'm working harder and I want to be able to eat in a way that reflects my hunger levels.)

What MFP does is counts on all non-exercise activity being the same, but varies how much you eat daily based on how much exercise you did that day. MFP attempts to match your eating to that same day's calorie burn instead of a longer-term average.

So with the first system you might set a goal of 2000 calories a day no matter what, and included in this is the assumption that you will burn say 600 calories every other day during exercise. (And if you don't exercise, you will end up overeating.)

If you set the same expectations of activity and exercise with MFP, your goal would instead be 1700 calories per day, plus exercise calories. So if you did 600 every other day, you'd still end up eating an average of 2000 calories a day. As you can see, you'd then be eating 1700 on your rest days, and 2300 on your exercise days. For some this works out better.

If you use the MFP system and don't eat back your extra 600 after you burn it, this is the same as using the other system with a goal of 1700 a day.

If you are setting a calorie goal, it should be for a reason, because there is such a thing as too big of a calorie deficit, and you don't want to undereat any more than you want to overeat. So if you determined that your ideal calorie range is 2000 a day and then you go and eat 1700 every day, you're doing it wrong.

A personal trainer is not a nutritionist.
If yours has you eating 1200 a day, then burning 400-600 calories, for a grand total of 600-800 calories net a day, he's an idiot. You can tell him i said so.

actually mathematically she's netting even less since 1200 calories was set up to already have her at a deficit

I don't understand what you mean by deficit when you say 1200 was already set up to have me at a deficit. Please forgive me, I'm just getting started and trying to do everything right.

Let us say that is just by doing your daily activities, you burn 1700 calories a day (this is known as your TDEE) and then you eat 1200 calories, you have created a 500 calorie deficit. If you then go and do additional exercise on top of your daily activities, say you run for an hour and burn an additional 500 calories, this makes your total calorie deficit 1,000 calories.

TDEE should also include exercise, it's your TOTAL daily energy expenditure and takes into account all your caloric needs

I meant if the exercise was above their normal activity level, then 1700 would be there TDEE on a normal day.

Of course by increasing their activity level they are increasing their TDEE.

someone please tell me what to do.

eat more food

and at 5'7 your goal weight is probably going to be close to underweight.

where did you get the 40% body ft from?

and given that you are close to your goal you should change your weight loss goal to .5-1 pound per week.

and yeah, eat more food

2 pounds a week is a lot to lose when you only have 30 to lose in total. If you do lose at that rate you'll be sacrificing lean body mass which is not a good thing; a slower loss is better for you and more sustainable. I would say 1 pound a week is much more achievable for the first ten pounds, and then probably down to 0.5 per week for the last twenty pounds. I've lost 10kg in five months, which averages out to a pound a week, give or take, but am now slowing down to lose 200g (roughly half a pound) a week because as you get closer to goal weight it becomes harder to lose the weight.