The FastDay Forum

Thanks, @carorees, so the answer might well be exercise? Funny how we come full circle again!

[carorees]

improbable but not impossible. there is certainly evidence that people with thyroid issues can have a TDEE at that kind of level. Undereating reduces thyroid function as well as reducing NEAT.

Thanks Caroline food for thought or ought I say less food that thought

[carorees]

I think you're exactly right there @kencc. I suspect that variations in thyroid function and insulin resistance together with miscalculation of calories taken in due to effects in the hypothalamus and reduction in NREE probably all add up to make the difference between those who lose weight easily and those who plateau/stall.

My new TDEE taking off 15% is 1272...quite low. Thanks for this thread @carorees.

[carorees]

MaryAnn posted about the same subject recently, with some interesting replies


5-2-diet-chat-f6/change-in-tdee-with-weight-loss-t11078.html

Thanks @izzy! I had looked for that thread before starting this one, but couldn't find it! I think I might merge the two.

... (even if I don't always understand the science stuff)

Good point on the related threads. It's easy to miss down there.

Keep reading. Even the scientific material gets easier to understand with experience.

:0

[carorees]

Merged!

I think the mere fact that we get a TDEE number calculated by the progress tracker lulls us into thinking that the number is an accurate guide to how much we can eat without putting on weight (we've all seen people saying things like "I've been eating within my TDEE and fasting and I'm not losing weight, I don't understand why"). When in fact, it is just an approximate estimate that is based on data collected from a large population, so if you're average, it may well be correct, but if you've been dieting for a while, have a non-average thyroid, are not average in your NEAT, are unaware of how your mind can play tricks on you in terms of how much food you have really eaten plus all kinds of other factors then there's a good chance that the TDEE calculation you're working to is not accurate for you. We need to remember it's just a starting point. If you're not losing weight after several weeks, your actual TDEE must be lower than you think!

Conversely, some people have continued to lose weight after entering maintenance. They have to conclude that their TDEE is higher than they think!

Yes @carolrees, exactly! In the tangle of it's more complicated than that... I appreciate you and your look at this tangle!

[carorees]

I found some papers comparing estimated TDEE with actual (by indirect calorimetry).

This one: http://www.ncbi.nlm.nih.gov/pubmed/20082662 found that the estimated values were particularly inaccurate for overweight or obese rather than normal weight individuals. Thus,

the variance among overweight and obese patients of BMI >25 was substantially higher compared to that among normal weight subjects of BMI <25, on whom the equations were based. The estimated REE by Schofield for an individual of BMI 35 kg m(-2), for example, could lie anywhere from 2.78 MJ (661 kcal) above the indirect calorimetry value to 2.59 MJ (618) kcal below it.

This one http://www.ncbi.nlm.nih.gov/pubmed/19853980 in overweight and normal Belgian women found

Most accurate and precise for the Belgian women were the Huang, Siervo, Muller (FFM), Harris-Benedict (HB), and the Mifflin equation with 71%, 71%, 70%, 69%, and 68% accurate predictions, respectively; bias -1.7, -0.5, +1.1, +2.2, and -1.8%, RMSE 168, 170, 163, 167, and 173kcal/d.

This, then suggests that the Mifflin equation used by the progress tracker can be 173 kcal/day out. That doesn't sound much but could be enough to slow weightloss significantly.

This one in postmenopausal Brazilian women http://www.ncbi.nlm.nih.gov/pubmed/23459971 found

All equations showed significant difference values for kcal/day (p<0.00001) (HB 1313.07±73.46; HR 1310.95±81.41; MSJ 1207.93±93.17; WHO 1375.73±61.01 and FBP 1250.05±73.54 kcal/day) in relation to RMRestimated (1063.79±157.82). The WHO equation was the one which most overestimated the RMR values with a difference of more than 300 kcal/day. None of the equations, in this study showed precision in the estimation of RMR, all prediction equations overestimated RMR values in Brazilian postmenopausal women, although the MSJ predictive equation showed the greater approximation of RMR measured for this population.

Combine the errors in the predictive equations with 'calorie creep' and it could easily be enough to stall weightloss.

I'm not sure that hunger before eating is necessarily a guide to calorie deficit when you consider the problem of leptin resistance, influence of macronutrients on ghrelin production, influence of blood sugar and insulin on hypothalamic circuits etc, etc. But on the other hand, not feeling hungry before eating is probably an indication that you are not in calorie deficit!

I feel a bit like screaming today, so much conflicting information coming out of the press lately...............I guess if I am losing weight then my TDEE is correct and if I am not then I am eating too much......simples.

A very interesting thread, thanks for all the good info and insights! I came to think of this in exercise terms, which might explain some things too:
When you do some exercise, some kind of program, your muscles and body tend to get very good at it. In running that's called "running economy". This means that the 3 K run, or walk, you usually do will spend less calories as it learns how to move. The body is very good at this. So the one hour Zumba dance will cost you a lot less 6 months after you started. I know this can't explain lower TDEE for everybody, but I guess it's a case of a lot of factors that add up.
Some trainers here promote "confusing your body" by doing/trying new exercises and shift food all the time - the idea being you mess up your body's plan to get more efficient.

[carorees]

I think there is evidence that skeletal muscle actually becomes more efficient metabolically following weight loss as well as the mechanical advantages you describe.

All these changes to make us more efficient would be a good thing if we didn't love our food so!

I haven't exactly been working out all the time I have been losing weight (born lazy), but I have been increasingly much more active, getting up more often,doing a small job that needed doing etc. I have also noticed lately that my little arm muscles have got a bit firmer....what's that about when I haven't been weight lifting??? My leg muscles are more defined too, but I put that down to being less fatty in the legs. Odd things are happening.

[carorees]

Just spotted this paper published last month with yet another formula for determining TDEE. http://ajcn.nutrition.org/content/early ... 6.abstract
Your thoughts @kencc?