If you follow MFP amount of calories to eat....

Each day is different .. unless you do the same thing every day.. food and cal burn via excercise.. you might hit it..

It's probably going to be a roller-coaster. Your weeks will consist of losses and fluctuations and you're going to learn to be okay with that. ☺

Age is already factored into the formula, along with weight, height and gender. Non issue.

If you eat a consistent # of calories and do a consistent amount of exercise every day, and eat the number of calories MFP tells you to eat, you will lose the target amount of fat per week +/- 10 % or so, because, yes, people are different but not all that different once the formula has been normalized for weight, height, age, and gender. The fluctuations in the scale are mainly water retention/dumping and also some fluctuations in solid waste making its way through the system. The body is a very complex machine (made mostly out of water) and while fat burning may be relatively formulaic and predictable, there's just too much natural day-to-day variance going on with other things to expect your scale weight to reflect that fat loss perfectly in the short or even medium term. But eventually, in the end, the scale will reflect the burned fat.

Cheat/off days can have a massive impact on things, more than most people realize. One egregious off day or drinking bender can easily add an avg 100 cals more per day for a month, or looked at another way, a pound of fat not lost. Aside from food measuring, that'd be another thing to look at.

lgfrie wrote: »

Age is already factored into the formula, along with weight, height and gender. Non issue.

If you eat a consistent # of calories and do a consistent amount of exercise every day, and eat the number of calories MFP tells you to eat, you will lose the target amount of fat per week +/- 10 % or so, because, yes, people are different but not all that different once the formula has been normalized for weight, height, age, and gender. The fluctuations in the scale are mainly water retention/dumping and also some fluctuations in solid waste making its way through the system. The body is a very complex machine (made mostly out of water) and while fat burning may be relatively formulaic and predictable, there's just too much natural day-to-day variance going on with other things to expect your scale weight to reflect that fat loss perfectly in the short or even medium term. But eventually, in the end, the scale will reflect the burned fat.

Cheat/off days can have a massive impact on things, more than most people realize. One egregious off day or drinking bender can easily add an avg 100 cals more per day for a month, or looked at another way, a pound of fat not lost. Aside from food measuring, that'd be another thing to look at.

The range can be more than 10%. That isn't common, but it can happen. The underlying data is in all likelihood some kind of normal distribution (i.e., bell curve): The further out toward the tails you get, the fewer instances. By definition, only around 68% of the observations are within +/- one standard deviation of the mean. Reportedly, a research-based estimate of standard deviation for RMR is about 6-8% of the mean value **. And that's RMR. When you're talking TDEEs or NEAT, you have to factor in the variability of daily activity and exercise intensity between different people doing "the same thing", so 10% (200 calories on a 2000 calorie budget) seems improbable as a practical limit. Research on fidgeting indicates that that alone can potentially (not commonly) account for something in the low hundreds of calories, for gosh sakes.

OP, you're conflating two different things, I think.

First, MFP (or any other so-called calculator) can produce an inaccurate calorie estimate for some people. For most people, it's likely to be close, because that's the nature of well-founded statistical estimates. For a few people, it will be further off, and for a very, very few, it could be quite far off. That's why we usually suggest that people believe MFP to start, stick to the routine for 4-6 weeks, then re-evaluate average loss rate and adjust calorie goal if necessary to lose at a sensibly moderate pace.

Keep in mind that MFP or other "calculator" is estimating your average calorie requirements, over a period of time that's representative of the usual variations in a person's activity level (weekdays vs. weekends, say, or even longer cycles). You actual activity does vary day to day, and there are also unavoidable errors in estimating one's intake that will average out over time (because one apple is sweeter than another, etc.).

That "calorie estimate is an average" idea, coupled with the fluctuations of scale weight because of normal, healthy water weight fluctuations (and daily differences in digestive contents still in transit), lead to the second of the things you're conflating: Your scale weight changes represent much more than just changes in body fat, even though body fat is the part we're actually trying to change when we "diet". Your day to day changes, maybe even week to week changes, have more noise than information in them, when it comes to understanding your fat loss. For premenopausal women, it can even be sensible to compare weight at the same point in two separate menstrual cycles, i.e., to look at monthly changes as being less "noisy" data.

So: MFP's estimate can be right for you (in the sense that you'll lose approximately the estimated number of pounds per week when you average losses over several weeks), but you'll still see the kinds of shorter-term variability that you report. Or, MFP could under- or over-estimate your needs, and you'll still see shorter-term variability on top of that. What tells you which scenario is true for you? Results over 4-6 weeks, maybe longer.

** More info about that here: https://examine.com/nutrition/does-metabolism-vary-between-two-people/

Anecdata: I need about 25-30% more calories than MFP estimates, in order to maintain my weight, while eating back all exercise calories. It's weird, unusual . . . but true, based on 4 years of logging data. Shrug.