Am I understanding this correctly? Please help

[CuriousLadyBird]

Hi,

I'm 5'7 and currently 106kg.

A calorie deficit calculator I've used saying to maintain my weight it's 2904 kcal.

So if I ate 1800 kcal and burnt off say like 600kcal - would my total intake be 1200 kcal meaning I have a 1700 kcal deficit or have I completely misunderstood it and if so please can someone help.

Thank you

In theory yes, that is exactly how it would work and you would have a 1700 kcal deficit. You would then, if you kept it up, lose weight until you were at whatever weight your body could maintain on 1200 kcal per day.

This is theory only, because in practice it falls down for a few reasons:

1. Caloric "burn" estimates as measured by wearable devices, fitness tracking sites, etc. are wildly, wildly off - anywhere from 30-90% off. This becomes even more of an issue as you participate in any form of exercise over a period of time and your body adapts to become very efficient at it - performing the work for as little expenditure as possible.
2. Caloric intake estimates are ALSO wildly off, again particularly on nutrition websites. Unless you are precisely measuring portion sizes and using the most accurate nutritional information possible, you're not eating the amount of kcal you think you are.
3. The caloric deficit you start with isn't the one you maintain as you lose weight. That number becomes smaller and smaller, and progress starts to slow down pretty sharply after a while.
4. Metabolic rates aren't taken into account by those calculators. They usually assume a certain average, which may or may not be correct, and then adjust from there. The assumption that you're eating 2904 kcal may or may not be a correct starting point. If your metabolism is slower, you might only be eating 2400, or 2200. There are very few accurate ways to measure this outside of metabolic research units.

So while yes, on paper that is a large deficit and would lead to weight loss, in practice it's more nuanced than that.

You shouldn't put your current weight into a calculator but your adjusted weight. Your excess fat does't count metabolically in the same way your organs do.
For your height, your ideal body weight is 62 kg, your adjusted weight is 79 kg. Use that number to calculate your TDEE.
https://www.mdcalc.com/calc/68/ideal-body-weight-adjusted-body-weight

I think you must have set your activity level quite high? I used to have similar stats to you. I set my level as sedentary and lose weight eating 1600 kcal a day.

I put my exercise as moderate which is 2-3 times a week but I'm planning on doing it everyday anyway but I don't know.

Thank you for explaining everyone, I'll just eat better, calorie count as best I can and exercise and hope this weight comes off.

600 kcal is a VERY high rate for a single exercise session. Most exercise doesn't begin to approach that level of intensity. The reality is that while exercise does burn calories, it's usually far fewer than estimated and as I said above, decreases as your body adapts.

I'm not saying exercise for fitness is useless, it's just a much smaller part of the puzzle than what is usually estimated in terms of caloric burn.

Also, by underpinning weight loss on exercise, there's more room for backsliding in a routine. You don't HAVE to exercise every day - sometimes you won't have time, sometimes you won't feel like it, sometimes emergencies will happen and you can't fit it in, or you have to travel, or any other reason that might keep you from that activity. You DO have to eat every day, so how much and what you eat is a greater priority and also far more in your control.

@gwenneh thank you. I was using 600 as an example in my OP I appreciate it's very hard to do that in a single session especially when I've never really done it before.

I'm hoping to do an hour or two on the treadmill (morning and night) mostly because we're going to Disney in October so I want to try and increase my stamina a little bit as well as pottering around as normal.

What would you suggest? I know you don't really know me and that's probably a stupid question but I'm really new to all of this and not sure what I'm doing really.

Exercise will make little difference. At some point, your body adjusts. You are using 600 cal on a treadmill, it will reduce metabolic processes to compensate.
It is the calories IN that count.

Okay thank you everyone. I won't go as hard in the thread mill but will still do it for Disney haha but I'll limit my intake to 1200-1400 kcal and hopefully that'll be enough.

Thank you so much for taking the time to explain all of this.

600 kcal/hour for a 100+ kg young person (especially males) working hard is quite feasible if they have the cardio fitness to actually work hard.

600 kcal/hour equates to a 12-15 minute mile for someone around 100 kg. That assumes an hour of consistent running at that speed, no breaks. Walking for an hour is about half of that in terms of calories, and both walking and running are activities the body adapts to really quickly - which will be nice for the OP given that it's prep for all the walking at Disney - but isn't really going to be conducive to a large calorie burn.

OP, I think you're going into this with good intentions and if you get a little more information you'll make a success of it. If I were in your position I wouldn't use any kind of calculator to determine your caloric intake; I would get a food scale and log foods very carefully for a week - change NOTHING, just log it, in accurate and honest amounts. At the end of the week, average it out and use THAT number as your starting point, then you can decide where you want to change your eating habits. And speaking from experience, the early part is the easiest because very small changes have the largest impact at that stage - just changing one or two habits consistently and not trying to overhaul everything all at once really will show results.

I tend to take exercise out of the equation entirely. So although I do exercise a few times a week and tend to do a minimum of 10k steps in top of that, I don't factor at if that into my calorie counting because I don't think you earn as many calories back as apps and watches would have you believe.