Is my logic correct (calorie deficit help!)

melaniebester

Hey there,

I've just been doing some maths about weight loss, and I need some honest (but not judgemental, please, my diary is open and you're welcome to look, but I don't want anyone's judgement here) help with understanding the logic around calorie deficit. Here's my math, could someone explain if this is correct? PS, sorry, I've worked in kilograms and kJ to some extent because I'm from Australia. Thanks!

To maintain my weight, I should be eating 2,269 calories per day.
I am eating 1200, therefore I'm at 1069 calorie deficit per day.
Multiplied by 7, I'm at a natural 7,483 calorie deficit per week already.

Over three weeks, I was generally quite significantly below that target.

Week 1 - 4569 calories below target
Week 2 - 4324 calories below target
Week 3 - 3521 calories below target

So, my total deficit for each week is:

Week 1 - 12,052 calories
Week 2 - 11,807 calories
Week 3 - 11,004 calories

Keeping in mind the general figure for 1kg of weight loss is 7700 calories of deficit. Dividing each deficit through by 7700 to figure out kg lost, I get:

Week 1 - 1.56kg
Week 2 - 1.53kg
Week 3 - 1.42kg

Totalling me out at an estimate of 4.51 kg lost over the three week period.

Now I haven't been able to weigh myself over this three weeks, as my scales batteries are flat and finances are tighter than I can explain at the moment for me. Is this an accurate method of calculating how much weight I should have lost? What other factors contribute? Is the real number probably more or less?

I'm aware I'm not hitting my 1200 calorie target per day, and that that isn't ideal, I am working on it, but I do struggle with getting there, which I know might sound strange to some considering my weight of 85kg and height of 165cm, but I honestly do have a battle with it, I'm not here for judgement on that, although if it comes into play with the weight loss side of things, I'm definitely interested in hearing about it.

Any opinions and advice welcome as long as they're reasonable and polite. Thanks!

EDIT: My BMR is 6,931.

365andstillalive

I think that you're meaning to say that your BMR is 1931?

Weight loss, by and large, is about calories in and calories out, so to a degree, without a scale you can know you're losing by eating below your maintenance calories; however, when you're signigicantly under-eating you can also have stalls in weight loss (and weight loss for anyone is not linear).

Basically, so long as you're eating below maintenance, you know you're losing.




I know you're not looking for judgement, but creating a 1000 calorie a day deficit by aiming for 700 calories below your BMR, you're risking some pretty serious health concerns. Especially since above that deficit, you haven't been eating to the 1200 mark you set, admitting that you've been coming in better than 1 lbs worth of calories below your target -- I also know you're being active, since we met through your other thread about home zumba.

You also have a post about feeling tired and hungry -- that's really because you're not eating even remotely enough and you are risking your health by doing so.

Weight loss isn't a short term thing, and with what you're looking to lose (around 40lbs) you're being way too aggressive. A 1-1.5lb loss is as much as you can healthily expect. When you only have 20 to lose, that drops to 0.5-1lb per week, depending on the person; your last 5lbs could take you two to three months to take off in a sustainable manner.

You've clearly already calculated your TDEE (2269) which is a great place to start -- but you're eating at TDEE -50/60%, when TDEE -20% is considered aggressive weight loss.

yarwell

I follow your logic, your BMR in calories is 1658 so you'll scare the "don't eat below your BMR" crowd.

If the scales aren't available you can track with a tape measure, or even a bit of string. With a BMI of 31 you can afford a high deficit for a few weeks at least.

Your real weight loss is probably less. You don't know your actual BMR unless you have it measured, and it may reduce when you restrict calories anyway.

One of the mathematical modellers (Kevin Hall, from memory) proposed that you need a deficit of ∼ 100 kJ/d per kg of weight change. It will take nearly 1 y to achieve 50% and ∼ 3 y to achieve 95% of this weight loss. Clearly your current deficit is too high for your objectives by this measure. If you want to lose 30 kg then a daily deficit of 3000 kJ is called for which is about half what you're doing now ie 720 cals/day deficit.

Your diary is closed, if you're struggling to up your intake I would say avoid any diet or low fat products or versions to increase your calories somewhat.

970Mikaela1

I've done that for a few months trying to find my tdee. the numbers usually matched pretty spot on with actual weight lost. plus more data points to go by will help you learn how you work.

MscGray

Not being judgy but it sounds like you are under eating. When MFP spit out that you should eat 1200 cals a day to lose (I'm guessing you chose to lose 2 lbs a week, or the Aussie equivalent), you should really try to eat as closely to that number as possible, as the deficit is already factored in for you. Making an additional deficit is only going to get you so far before your health may start to suffer, because you may not be getting proper levels of nutrients. (not to mention if you exercise at all, your body just wont have enough fuel). Remember that weight loss isn't an exact science, you've done all this math and that's fine but just use it as an idea of how much you MAY have lost. Don't step on the scale and not see that significant of a loss and freak out. There are soo many other factors that go into it (water retention, TOM, etc). Like others have suggested, measurements or string will help you track the changes your body undergo as well as, if not better then the number on the scale will. Good Luck to you!

mazh4r

I have a lot of time on my hands and decided to use excel to compare my deficit, how much i loose theoretically, and how much i actually lost on a weekly basis. Basically, in after 4 weeks, i lost 6 pounds when i was theoretically supposed to loose 7.5 lbs. to me it is pretty accurate, and i was able to see my "bad week" theoretically and how it correlated with my actual weight. idk how to post a screenshot of the sheet on here so you can get an idea, but for the most part it works in unison theoretical and actual.

As for the undereating, as long as you're aware of it it shouldnt be a big deal if you know its temporary. I heard it from a friend that when you slowly switch from loss mode to maintain mode that you should make the transition slowly. for example atm im at 1500 kcal/day. and if i want to maintain at 2000 kcal a day, im going to have to slowly make the transition from 1500 to 1700 etc over a few weeks. so with that regard you dont have to suddenly start eating to maintain, just slowly bring it up. againt his is what i heard from a friend whose successfully lost weight. hope this helps!

kgeyser

Yes, eating below 1200 has consequences with weight loss. It means you are not hitting your nutritional needs, your body is eating away at your muscle, and you'll be left a flabby mess with a lower number on the scale. Not to mention fatigue, hair loss, impaired mental function….oh, and that eating away muscle thing? Doesn't just apply to your arms and legs. Your heart is a muscle and is also fair game.