Quick question, lovely forumites - I have a BodyMedia armband, which tells me that I've burned over 3100 calories today. I've only consumed 1350, which leaves me at a 1700 or so calorie deficit. Is this problematic?

I know that going below 1200 calories a day is a bad idea for women, but I've also heard that daily calorie deficits of over 1000 can actually make it harder for the body to lose weight, as it starts to think that it's actually starving and freaks out. True? Not true?

From what I've read it's your caloric intake compared to your basal metabolic rate (calories you burn w/o exercise) that you need to watch out for. I've seen nutritionists write that if you consume less than 50% of your bmr worth of calories you may experience a large decrease in your overall metabolism. Again, this is gleaned from several sources and you will find many people here who will contradict expert opinion with their experience.

That said, how are you feeling? If you are feeling good and losing weight, I say go with it.

I agree with above...how do you feel? Are you still losing weight? If not, I'd might try bumping up your calories.

I've been sticking to about a 1000 calorie deficit, save for today, when I ran/walked 7k and did four(!!!) hours of house-cleaning.

I feel fine now. I had a small snack and I could eat something more, but I don't feel particularly hungry. That said, I'm a little concerned that the high deficit will mean that tomorrow I'll be extra hungry and end up either bingeing, or simply eating waaaaaay more calories than normal. I suppose, worst comes to worst, I could just eat my maintenance calories and give myself a rest day?

If you are hungrier today, eat a bit more. By a bit, add in a couple snacks to avoid a binge.

One day of a very high calorie burn won't throw your body off, but day after day is not good. Your body would need more fuel to keep up.

Ok,
heres the deal
the Body Fit Media, Body Bigg, Go-Wear Fit, FIt Bit....... they arent gospel truth. I AM SORRY. YOu are a small Female, which makes it even MORE inaccurate.

These devices are based on the exact same calcualtions you can plug into a website calorie tracker/calcualtor.
They are certain algorithms, most use the HArris -benedict, that compute your "supoosed" cals burned, but its based on the AVERAGE woman, of YOUR HEIGHT, and YOUR WEIGHT, and YOUR MOVENMENT. But guess what? we ALL have vastly vastly different metabolisms. The Fit Bit or whatever is stall making asumptions and giving estimates, and these devices NOTORIOUSLY overestimate, ESPECIALLY on smaller, conditioned females.

WHat they ARE really great for, is giving you a really good idea of how much yoU MOVE in a day--> your NEAT Levels (Non-Exercise Thermogenesis). This is where the fat loss battle is one wonAt your height and weight, 1300-1400 is VERY appropriate calorie level for you. You can try bumping it up a little, and see if you lose still, and if you do, THATS GREAT

With regards to "starvation mode". Its a myth. What ANY PERSON will experience ON ANY DIET, no matter HOW AGGRESSIVE is a metabolic adaptation. How quickly your body begins to adapt is based on you, how aggressive the deficit, how sensitive your body is to fat loss, if youre a chronic dieter, etc. Your body adapts by lowering your Basal body temperature, lowing your Ambient and resting Heart rates, slowing growth of hair/nails, shut down of reproductive processes. Basically, anything that body can do to burn less calories, it will start to do, and that means shutting down, or slowing down all NON_ESSENTIAL functions.

You asked if your deficit was too aggressive? Only you can know how you feel.
But here is one of the best indicators:
If your period starts acting in ANY WAY that is Irregular FOR YOU.... that is a sign that adaption is occurring and your body is STRESSED. It is a key vital for women. You may start having more frequent periods, lighter periods, spotting in between....longer in between periods, and thn suddenly......its gone

If your body's metabolism is already a little wonky from previous dieting, than your Body Media is going to be even less accurate, and your maintenance cals are going to be even less then they should be

Too large a deficit for too long will be a problem for a number of reasons but a single day here and there means nothing.

A 1000 calorie daily deficit is too much for someone your size but then again as MK mentioned a Bodybugg is not always extremely accurate.

and to add to what JohnP said, and in regard to the innacuracy of the Body Fit Media-- it is unlikely that you are sustaining a 1000 cal deficit. Your probably burning CLOSER to 2000 a day, a little more on active weekends
Trust me, if you were hitting a 1000 cal deficit REGULARLY/DAILY you WOULD FEEL IT.

If you go too low you may find yourself lethargic and laying around all the time. But then, you may not. It depends on what you eat, your specific metabolism, size, etc.

Your metabolism may slow some only if you drop weight, not because you're eating less. With the above in mind, remember that biology dictates that the larger the calorie deficit, the more weight lost.

Just curious to know what you could be doing in your day, at your height/weight, that could make the armband think you're burning those kinds of calories? Do you have a really high resting heart rate or something?

It's a combination of things. I'm a street fundraiser, so I'm outside all day standing and walking around getting people signed up for charities. Yesterday I didn't work, but I did run/walk 7k and also did a lot of walking around doing errands and then spent 4 hours doing housework. I also don't have a car, so I walk more in general. That said, the BodyMedia is noticeably inaccurate whenever I take the bus or a taxi, so that's bumping my calories burned up by 200 or so more than they should be on a daily basis.

Also, I have an IUD which has entirely gotten rid of my periods, so that's not something that I can use to track any stress to my body.

If the number was very different on that particular day, maybe it was something you did in the housework. I read a review of a monitor (armband) by Lyle McDonald and he said it showed strangely high readings if there was a lot of repetitive arm motion. Like, scrubbing something?

Otherwise, I don't know what to say, except that my days sound pretty similar (I'm a teacher so I do lots of walking around and gesturing) and I'd love to get burn rates like that because I could eat a lot more than my current 1900 cal/day maintenance! Maybe I can borrow one of those things somewhere.