Calorie requirements

I have been trying to find out exactly how many calories (or kcal) I need to consume to exist. This is not as easy as I thought it might be.

• From somewhere my Fitbit has be using 1635 per day just from existing. That is, on a day when I haven't had it on or recording, it calculates that is how many kcals I will have used. How it comes to that conclusion, I'm not sure. 

• HealthStatus (a website) calculated my existence to require 2689.8 kcal a day.

• BBCiWonder came up with 2240 kcal.

There seems to be a general consensus that 2000 kcal is what women need in order to maintain their weight, keeping the engine ticking over so to speak. But that takes little or no account of age or weight.

There is a formula or something. Doing a bit of reading it seems that requirements (no matter what the answer comes up as) seem to be calculated from the basal metabolic rate (BMR) and that is calculated from body weight, height, age and gender. Which is the same no matter what on-line calculator you use. So how can they differ so much? Who am I supposed to believe?

The amount of kcal you need to lose weight is a whole new ballgame!

• HealthUnlocked (website) suggest 1400 kcal.

• NHS Choices say 1692 - 2175 kcal

• and MFP wanted me to start on 1230 kcal!

So where does all that information leave me? And lets not forget, we're only talking about calories here; the components and proportions are as yet, undiscovered by me. It's surely going to get way more complicated the more I delve into it.

• To function on a daily basis I require 1692 - 2689.8 kcal per day. That's a hell of a margin for error!

• To maintain my weight the consensus is approximately 2000 kcal

• To lose weight, guidelines (see previous post) suggest 600 kcals less than maintenance. So is that 1092 kcal, 1400 kcal or 2089.8 kcal? Answers on a postcard please!

I have set MFP to 1800 kcal per day and I will see how that goes for a while. I am hopeful that in the short-term as it is considerably less than I have been eating I should show some weight loss initially. This may need to be adjusted as I (hopefully) lose weight.

I've started something here that is going to be a long term project, perhaps even more so than my MSc!