If a sedentary person shoudl eat 1200-1500 calories per day to lose weight

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and I ran 10 miles today, which would have used 1000 calories, does that mean I can have 2200-2500 calories and still expect to lose weight? 1mile running = 100 calories.

It seem to make sense on the basis that to lose weight you need to eat less than you use, but it also seems too high. I'd be amazed if I actually did lose weight. I run approx. 40 miles per week, so does that mean I can/should eat 4000 more calories per week than a "normal" dieter?

People keep telling me that a reason for weight loss stalling is not eating enough, but I don't understand the science/maths of that.

I don't think you are eating enough either. I do hardly any exercise, am slim and stay stable on approximately 2200 per day.

I believe that not losing weight because you don't eat enough is due to your body switching to starvation mode.

If you don't eat regularly and enough calories then your body believes it is starving and will absorb all the fat/calories from every bit of food you eat to store for later.
If you eat enough food regularly then your body doesn't store all the fat because it knows it has plenty of food in supply and has no need to store any for later and so gets rid of any excess.

However the amount of calories you need really is specific to each person. My GP told me for my height/build/lifestyle I only need 1100 calories per day while still running 3 miles per day (mon-fri). I would need to reduce my calories below 1000 to lose weight. However my friend needs 1900 per day (she runs with me) due to her height/build etc

Also muscle weighs loads more than fat so you should be looking at losing inches rather than weight.

You should make an appointment with your GP or a personal trainer/fitness instructor and find out how many calories you need.

Agree that trying to loose weight is a pretty useless aim to. Also agree that its the inches you should be keeping an eye on.

This tells you how to measure your waist and hips properly and how to work out the ratio. It also tells you whether your ratio is healthy or not.

If your ratio is healthy I just eat normally and not worry about counting calories

I think if you run regularly your body becomes quite efficient in its use of energy. I would probably only eat back half of the calories, so add on 500 more and have around 1700 for the day. Thats a good amount of food so you shouldn't be hungry.

My understanding is that you always have to net your 1200 cals. So if you eat 1200 but exercise 1000 you only net 200 calories. Good luck

Doesn't look like the OP is coming back anyway pause.

Roses, what exactly is your height and build?! That can't surely be right with the running added?!