Advice please. Coming off the camebridge diet

You should never eat less then 1200 calories. That is the very LEAST you should eat, you really should get more then that though. I think you need to do a little research and figure out your TDEE, and read up on nutrition some. Good luck to you!

Here is a website to help you figure out how many calories you should eat. http://scoobysworkshop.com/calorie-calculator/

I'm sorry to say, everyone I've ever known that has done the cambridge diet has gained all the weight back they've lost, plus some. My advice would be to never have done it in the first place, but hey, it's too late for that.

800 calories is still far too low, and 2lb a week loss is far too aggressive for someone with only 10lb to lose.

Set your MFP to lose 1/2 lb a week, put your activity level as sedentary, then log and eat back your exercise calories. You will gain weight in the beginning, there's no doubt about it, (although a lot will be water weight), but that's the problem with coming off of a VLC diet. But if you can swallow that initial gain and keep at it, the rest of the weight will come off in due course, and in a healthy way.

I know that's probably not what you want to hear, but what is more important, being 10lb lighter or not damaging your body any more?

Also, scrap the deadline. This needs to be a lifetime change, not a quick fix.

Fad diets make my angry

people are right that 800 is way too low, but it's ok to be concerned about putting the weight back on by suddenly going back to a more appropriate calorie goal. You may think about upping gradually: if you have been at 800, go for 1000 for a week or two, then up to 1200 for a week or two, and gradually like that until you get to whatever you decide will be your goal. (another couple of weeks under 1200 isn't going to kill you). Many people do find they gain when they first up their calories, but it does eventually level out. By doing it gradually it gives your body a little time to get used to the additional calories.

what's important to realise, is that a proportion of the weight that you lost was water weight, and you will gain back the water weight when you start eating normally again. It's important to realise that this is not fat, so gaining this weight back again will not make you fatter. When you eat less than you burn off (even on a much more sustainable diet with a small calorie deficit) some of what you burn off will be glycogen, and glycogen is stored as water. This is your body's short term energy store. Fat is your body's long term energy store. To lose weight the healthy way, you want your body to burn fat. Some burning of glycogen is inevitable, and when you switch to eating at maintenance, your body will start storing glycogen again, along with water, so you see a weight gain. Your body won't start storing fat again, unless you are eating more than you burn off. So don't freak out about water weight gains (and similarly don't fall for crash diet plans again, because a lot of what you lose on them is water weight). Having more glycogen is good for you, because it's your body's short term energy store, and you'll feel more energetic when your glycogen stores are high. People who run marathons sometimes run out of glycogen before they finish the marathon, this is "hitting the wall" and suddenly they can't run half as well as they could. Trying to exercise with no glycogen in your system is like trying to wade through treacle. So you want glycogen in your system.

To avoid fat gains (you probably did lose fat on this crash diet), you need to make sure you don't eat more calories than you burn off. If you calculate your calories with a calculator (e.g. katch mcArdle formula) that will give you your BMR (how many calories your body need to run itself) and you can use an appropriate activity factor to calcuate your TDEE (all the calories your body uses, including activity and exercise... BMR + activity/exercise calories = TDEE) - you need to eat less than your TDEE, but for health and sustainability reasons, you should eat more than your BMR. As you've been on a very low calorie diet, your metabolism may have slowed a little (this is a survival response to eating too few calories) but if you eat more and exercise, you can speed it up again (but like I said, expect water weight gains, and don't freak out about them, because they're not fat) - the usual advice is to increase your calories by maybe 100-200 a week until you're eating at a number that's below your TDEE, but not too far below. You should ultimately aim for slow and steady fat loss, because then you can be sure that it's all fat that you're losing and not healthy tissue (if you eat too little for too long your body will burn muscle for energy) - also this is more sustainable in the long term, and there's much less risk of gaining it all back again. When you increase your calories, like I said, expect water weight gains, but this will only be for the short term, once your body's glycogen stores are full, you will start to lose actual weight again, and even if you see a water weight gain on the scale, if you're eating less than you burn off, you may have lost fat, just it won't show on the scale if you also gained water.

Regarding BMI and success at IVF... this depends on the actual amount of fat your body is carrying. water weight gains or losses won't affect this. You need to actually reduce the amount of fat, and the above advice, i.e. eating between your BMR and TDEE will help with that. Aim to lose 1-2lb a week, any faster than that and it's unlikely to be just fat you're losing, as the body can only burn so much fat in a week. Slow and steady fat loss, through sustainable changes, is what's going to make you lose fat and keep it off for good.