I'm sure someone can point to a good writeup on this.
I'm a firm believer that this explains a ton with initial success, later failure, and a host of sub questions.
All food we take in has to be digested, absorbed, or eliminated.
This process is largely regulated by gut bacteria. We are amazingly adaptive creatures with amazing guts.
Most diets work short-term , I believe this is due to caloric restriction. Inadvertant restriction. As we change our dietary intake drastically, our guts have to adapt to the new caloric source.
Now before we explode into calories in vs out debate, this is calories in vs calories absorbed, an inadvertent restriction in calories
Those people that eat all they want without gaining weight likely have horrible gut health and poor food absorption
Those of us that look at food and gain are simply efficient
Those of us who lost heavy, and started regaining may have simply healed our gut and adapted.
I say this for people eating static amounts, the obvious solution is to be completely honest with your body and not follow societal eating norms and only eat when and portions as you feel you need for satiety.
I find I eat less now than when I started, yet I'm still packing on muscle... But my eating schedule is now erratic ...
Thoughts? Studies? Writeups?
Edit: to clarify, I'm talking calories absorbed(regardless of partitioning) vs calories eliminated thru waste. A more efficient gut would dump less calories, break them down to be used better.
If you eat 2000cal and you're pooping out 500 cal, presumably your body has 1500 to partition how it pleases.
If you eat 2k cal of different food your gut isn't used to and you poop out 1000cal, you're at a 500 defecit from before( we will presume no other hormonal or macro changes)
As you continue eating adaptive diet, your gut "learns" how to extract these new calories and defecit ends.
Gut bacteria and enzyme adaptation barring thermal and hormonal changes, I think play a great role in weight.
I'm looking for info on calorie absorption for those eat 7000calories don't exercise but don't gain weight people. Food in vs waste out, gut biopsy etc.
The fecal transplant tests seem to coincide with my theory as well as changing out te bacteria changes absorption and near immediately affects weight. Mind you I don't think bacteria are the sole reasoning, we are far too complex hormonally for that. But I think they are major major players.
To me this makes logical sense why all diets work at first then ultimately fail, and why quality bacterial change an hormonal change is the only long term solution( paleo does both)
Nephropal just did a great writeup: http://nephropal.blogspot.com/2011/01/intestinal-flora-and-obesity.html