The FastDay Forum

Study from 1989 http://ajcn.nutrition.org/content/49/2/ ... l.pdf+html

Summary of 63 subjects monitored in a metabolic unit. "To compare energy requirements in obese and nonobese individuals, body composition was examined in 63 women whose true energy intake and body weight were monitored in a metabolic unit for an average of 36 d"

Conclusion was that energy requirement for weight maintenance did not depend on adiposity but primarily on lean body mass.

Derived a regression equation :

a) kcal/day intake = 881 - kg/day loss * 6292 + lean body mass (kg) * 33.8
(R^2 = 0.6)

a less good equation was :

b) kcal/day = 1550 - 6590 * kg/day loss + 13.3 * weight (kg)
(R^2 = 0.5)

Under-reporting was very common but not greater in overweight subjects.


Using the above equations for a couple of examples :-

100 kg, 50% fat, 2 lb/week loss, calories eaten a) 1755 b) 2025
80 kg, 40% fat, 1 lb/week loss, calories eaten a) 2095 b) 2187
80 kg, 40% fat, 2 lb/week loss, calories eaten a) 1687 b) 1759

Spreadsheet link

[carorees]

This is very useful for our forthcoming study!

I got this to fit your data, by using 90 kg and 49% fat (aka 45.9 kg lean mass) with a loss of 14 kg over 120 days it pops out with a food intake of 1698 kcal/day average which matches my tweaked numbers (I inflated your Christmas intake to get a less silly TDEE that week).

At 80 kg that would be 42.7% fat. Maybe we can reconcile your results after all, especially as the above equations have a substantial error band - think I'll add that to the spreadsheet.

[carorees]

So what do you get my TDEE to be? And, more importantly, can we use this to help others to calculate their TDEE more accurately? What kind of % error in calorie counting do we assume?

My energy requirement calculated by the fat secret app to maintain body weight is 1900, which is higher than all the online calculators I've used and so seems to be nearer reality (for me anyway).

If I set the weight loss to zero the above equation a) predicts a food intake of 2430. That's effectively what it thinks your TDEE is.

Were Katch-McArdle to be accurate for you the ratio of this TDEE to BMR would be just under 1.8 which is pretty high. However your reported intake of over 1600 and weight loss of 1 kg per week require a TDEE well into the 2000s by any measure.

I don't think there's a lot of point in telling people their TDEE to be honest. The 5:2 Fast Diet advocates "a quarter of your recommended calories" after all, not a quarter of a number that is unknown to you. I tend to see TDEE abused as an overeaters charter, simpler to look at rate of weight loss and adjust accordingly - the trending apps like Libra or the Hacker's diet web site do that, they tell you the effective calorie deficit from your trend line.

Anything mathematical has a single conclusion - if your weight loss is too low or zero you are eating too much. Even Hall's sophisticated dynamic models yield the same conclusion.

We could use these equations to inform users what the maths thinks they're eating, leaving them to rationalise any differences.

[carorees]

I'm still bemused as to how my TDEE could be so high though? Looked at my Libra calorie deficit and it's saying -1579kcal/day! That's ridiculous!

Anyway the answer to Phils question is.............



Yes, if they aim on staying overweight.

I'm still bemused as to how my TDEE could be so high though? Looked at my Libra calorie deficit and it's saying -1579kcal/day! That's ridiculous!

Find yourself someone with the kit to do measurements for you - sports science department at Uni perhaps, specialist sports shops / gym etc. I can point you at a facility in London but it's not dead cheap and you have to get there.

I retain this nagging doubt about your scales but I'm a cynic.

[carorees]

Phil, even if the scales are inaccurate, they can't be that far out regarding the change in weight surely only the absolute value? I do jump on and off several times to be sure.

Phil, even if the scales are inaccurate, they can't be that far out regarding the change in weight surely only the absolute value? I do jump on and off several times to be sure.

If they are wholly inaccurate then their output is meaningless from my perspective. You're hoping that there's a zero offset only and the slope of the measurement is correct, which might be the case or it might not.

I wouldn't want to speculate about how repeatable or otherwise they might be or what the general failure / inaccuracy mode is.

To find out you should get four 20 kg bags of coal and three 1 kg bags of sugar then do a regression analysis of the 4 data points.

Of course they may be right and you will have other observations to support or deny it, but if we're multiplying a 1 kg scale reading by 6000 - 9000 calories small errors have large consequences.

[carorees]

Ok, I have bags of horse feed that weigh 20 kg, plus diving weight belts in various weights...I'll experiment!

I think it is the weight loss from the starting point on your own scales that matters - gym scales for example always weigh a certain amount heavier because its a different time of day and you are wearing shoes and clothes...

I checked my scales using bags of flour. All's well with them.
And I try to write down everything I eat and round calories higher than lower.
But if I don't have my correct TDEE, I do nothing...