Can someone clever explain this? (Calories and maths)

[RoryGlory]

Going by the table below I need -410 calories a day to get to my goal.

If my resting metabolic rate is (I believe) 1800

So if I eat 1200 calories a day I have a deficit of 600.

So 1200 - 600 = 600

So to get to -410 ... I would need to burn a further 1010 calories? Is that right?

See, as a scientist and a fitness enthusiast, I'm appalled by this.

But then my evil scientist side is saying.... wait a minute, this is a rather interesting experiment, and one that no ethics board would ever approve

I mean, there has to be a practical limit on how much energy you can recruit from body stores, there's enzyme turnover, cofactors, there's waste products to dispose of....hmm.
I know there's a limit to muscle glycogen stores, hence 'hitting the wall' in a marathon etc, obviously you'd be using a proportion of fat as well depending on the training intensity.
Then on 1200 calories you won't be able to top up those stores properly overnight... I wonder if you'll go into ketosis? Have you thought about what macros you're aiming for on your 1200 calories?

Can you come back on here and update us on what happens? Or I can PM you my username on MFP if you're planning to track on there?
If I have a slow morning at work I might have a look through the literature and see if anyone has studied this. Probably not, as I say, it would be highly unethical.

Also, given the disruption to your metabolism, electrolytes etc, that's likely to have a nasty effect on your heart and there's a fighting chance you could drop dead. Can you arrange for someone to update this thread if that happens? Otherwise we'd never know and other people might think this sounded like a good idea.

Why would I?
Because your body will reduce your BMR to account for the lower calorie intake. It’s evolution’s way of preventing you from using more energy than you have available, to help you survive a famine. That’s why anorexics feel cold and grow fine hair all over their bodies. Then your maintenance calories will be less so you’ll regain weight more easily.

Oh good grief.
The sums are right but you don't want them to be.

According to my Gardiner, running a half marathon burned 1331 calories.

To hit her target, OP needs to burn 300 MORE calories every. single. day.

I have no idea what kind of exercise will sustainably allow that?!?

Or what kind of lifestyle allows that time commitment?!?

Ha ha 'Garmin'

I did wonder Fusion although I thought you must just have a gardener who is very into running!

@FiveNightsAtMummys it's easy to lose weight fast if you're big {not suggesting you are, of course) but OP's TDEE is about the same as mine, as a 5'4, moderately active middle aged female with a bmi of around 25, which is why she needs such a massive calorie defect to lose at that weight.

@SonEtLumiere that calorie defect is only enough to lose a pound a week. OP really is wanting to create a 2200 (ish) calorie defecit, each day. Fine if you're morbidly obese. Impossible to do healthily if you'd rather be 8 stone than 10.

Heathen

@PickAChew, I was big for me (bmi 31) it's now 20! I can still loose around 1lb a week but I do have to eat around 1300-1500 so that makes sense thank you

Starting at first principals. Each pound is worth 3500 calories. You need a deficit of 3500*28 over 44 days. That’s 98,000 calories over 44 days or 2,227 per day deficit. If your BMR is 1800- then without eating anything you burn 1800/22,227. Meaning you need to burn a further 427. So you need to burn 427 calories plus whatever you eat each day. If that’s 1200 cals, you need to burn 1627 calories per day.

Obviously that’s 1800/2,227

Oops @HobbyIsCodeForDogging beat me to it!

@TheHeathenOfSuburbia I'd be genuinely fascinated to see your anaysis of how this goes with broad strokes of "Rory experienced this, which makes sense because this is the point we'd expect A and B to start kicking in".
Theres so much diet and exercise stuff out there but so much is frankly guesswork based on fuzzy data by people who don't understand that there is more than one simple "you ate x less so must have lost y" going on.

As an accountant who deals with numbers all day every day, all I can say is:

Thanks for the drop dead comment. I won’t be updating you on any part of this.

I don’t get why people are making this out to be difficult.

I’ve eaten 1070 calories today and according to my Fitbit I’ve burnt 1708

So I’m already on -638

(Obviously I’ll be having dinner later but I’ll naturally burn more calories too)

I’ve eaten 1070 calories today and according to my Fitbit I’ve burnt 1708*

But nearly all of that will be your basal metabolic rate - and since we're 2/3rds of the day through the day (Fitbit measures midnight-midnight) you're not doing to get more than another 500 or so out of that. If you're going to start counting your BMR as calories burned then you need to add it back on to that 1610 calories you need to burn each day, so you need to burn 1610+1800=3410 - and you're nowhere near that, and if you want to be you need to send off on your half marathon soon so it doesn't get dark during it...

And I've sat on my arse, much of today and my fitbit says I've burnt 1300 calories. That includes my bmr on top of the walk to the shop and bit of housework I've done. Walking 1km, doing 3 loads of laundry and ironing school uniform certainly doesn't burn that many calories.

With a defecit of 638 calories, you are on course to lose about half a stone by your deadline, plus maybe a bit of water weight. To refer back to the thread title, your maths is very wrong.

Ah, Fitbit calories, ok, i see.

It's hardly fair to imply i told you to drop dead, it would be irresponsible of me to be aware that was a possibility and not advise you of it.

I lost 27lbs in 42 days a couple of years ago - I ate 800kcal a day on the Cambridge Diet. I did no exercise and it wasn't particularly difficult as I was in ketosis.

For a short term fix, it can be done.

Wow! There's lots going on on this thread.

I’ve eaten 1070 calories today and according to my Fitbit I’ve burnt 1708

So I’m already on -638

You're misunderstanding it. The -410 doesn't mean you need to eat 410 calories less than you burn. It mean that each day you have to burn off 410 calories + your basal rate + whatever calories you've eaten. So even if you eat nothing else today you still have to burn off around 1500 calories more.

Just do the Blood Sugar Diet or Fast 800 and forget about the maths. They work, they're not unhealthy and the weight loss and fat loss has proven health benefits. Add exercise as recommended in both plans.

What?!? I don’t get this at all!

I’m just told so many different things it’s hurting my head

If I eat 1200 then how many calories should I have on my Fitbit to get to get my deficit?

(If I don’t touch my Fitbit then it always says I burn 1574)