Elizabeth Miller wrote:

>I am reading a book called Body Heat by Mark Blumberg. He talks about
>research on Diet Induced Thermogenesis, the phenomenon that's supposed to
>keep us from obesity. Overeating induces DIT according to the research; the
>body supposedly 'wastes' the extra calories via brown adipose tissue (BAT).
>Studies on rats have found that when allowed to eat cafeteria style all they
>want, they will eat 75% more food, but instead of gaining weight, their
>metabolic output (heat) increases 75% so weight-wise it's a wash. Blumberg
>says this implies that obesity results "from an inability to burn off excess
>fat, not from mere overeating." Blumberg goes on to explain that wasting
>energy is not all that's involved in preventing obesity. Apparently the
>percentage of protein in the diet is crucial too -- but he suggests less,
>not more.
>

This seems odd.  I'd like to read this book to see what his research
shows.  Everything I've seen indicates that protein is more thermogenic
than carbohydrate or fat.

> He says if a human had access to abundant sources of low protein/
>high fat food -- he would store the fat, raise his leptin levels and then
>stop eating.
>
I think this is true, but the problem seems to be the setpoint at which
the leptin kicks in.  If, for example, the leptin turned off appetite
when body fat exceeds 12%, this would be great.  But we know that this
is not always the case.

> He should have a lot of energy from fat which he would burn off
>as heat. But when he burned off the fat energy, he would be hungry again and
>would eat another meal of low protein/high food, burn it off; eat a third,
>burn it off until he had enough protein. Thus DIT is useful not only as a way
>to prevent obesity, but to insure that we get  necessary nutrients.  Here's
>the suprize: He claims that "For humans, when the diet is made up of 12%
>protein, DIT is minimal (for rats it's 20%). Below these values, DIT
>increases steadily. Above these values, heat production also increases, but
>as by-product of the digestion of high protein diets; this is not DIT, but it
>is wasteful.
>
But "wasteful" is what we want, isn't it?  It means that we have to do
more metabolic work to digest the food, which in effect raises the
metabolic rate.  If we take two meals of equal calories, one 50% protein
and 50% fat, the other 12% protein and 88% fat, we will need to use more
energy to proces the first meal.  That, it seems to me, means that less
of that meal is available to be stored as fat.

>The trick might be to eat a diet comprised of no more than 12% protein and
>the rest fat.
>

Well, if 12% protein is the point at which DIT is minimal, but increases
as we reduce protein, we'd want to be sure to eat substantially less
than that to maximize DIT.  But then I think we'd have other
difficulties.  I diet of, say, 6% protein and 94% fat would almost
certainly be deficient in terms of micronutrients.  On a 2000 calorie
diet, that would be only 30g of protein, which doesn't seem like enough
for routine tissue maintenance, etc.  To utilize all that fat we need
carnitine to transport it into mitochondria.  Normally we get carnitine
from animal protein, or we synthesize it from other amino acids.  On
such a low protein intake, I wonder if this would be a problem (Maybe
not -- I don't know how much protein is needed for carnitine).

Anecdotally, I find that I gain weight if my lowcarb diet is also
low-protein.  After a while, I seem to develop an insatiable appetite,
and I tend to eat large quantities of these low-protein, high-fat foods.
 It's possible, though, that this would change if I did it longer.

Todd Moody
[log in to unmask]

> We know that if carbs are thrown into the mix, we move into fat
>storage territory which of course would have been great as a seasonal
>response to carb supply to help us survive winter/non-fruting season coming
>up, but it's something the majority of us probably don't need. I confess that
>because of my years of low fat eating and the brain washing I've endured in
>my Nutrtion education, I tend to 'justify' the fat that I eat as part of
>eating protein -- it's still hard for me to eat just fat.
>