Metabolic Advantage: The Final Answer

A little background first:
The conventional wisdom is that weight loss depends on a simple comparison of calories ingested vs. calories expended.  Consume more calories than you burn, you gain weight.  Consume fewer, you lose weight.  Simple physics. 
Some people claim, for a variety of reasons, that this is false.  For example, many low carbohydrate proponents argue that if you eat fewer carbohydrates you can consume more calories total without gaining weight, or even lose weight while eating more calories.  Perhaps a low carb eater could lose weight on 2200 kcal/day while his twin brother living on 2200 kcal/day of pasta and bagels might fail to lose weight or even gain weight, even if their activity is the same.
If you care to investigate this you can find a really large number of studies and arguments thrown back and forth between these people.  The truth is difficult to determine for a number of reasons:

1. Certain diets make you lose or retain water.  Don't believe me?  Add 10 g of salt to your next meal.  Salt has no calories.  I promise you'll gain "weight."  Not fat or muscle, but weight.  It's not meaningful in the sense of proving or disproving anything about metabolism.  I haven't broken the laws of thermodynamics; please don't send me to physics jail.
2. Calories in food are VERY hard to count.  Know how they get the calorie counts on a food label?  They put the food into a bomb calorimeter. It burns the food (literally) and measures the energy output.  Know what happens when you put a twig into a bomb calorimeter?  You get energy.  Do you think eating a twig will make any difference in your body mass?  No - your body can't metabolize wood.  Repeat after me: my stomach is NOT a bomb calorimeter.  So if you eat a high fiber diet the calorie counts on the packaging will overrepresent the amount of energy your body can actually get from the contents.  A 100 Calorie pack of food with 5 grams of fiber only has 80 Cal of energy that you can actually use, unless you're a woodpecker.  Boom - anybody on a high fiber diet will seem to have a metabolic advantage that is the result of bad measurements.  Does that mean a low carb, low fiber diet is bad for weight loss?  Not exactly. 
3. There are legitimate and inarguable scientific reasons why certain macronutrients give you less net energy.  There is a thermogenic effect of eating that varies - eating protein causes a loss of heat energy that you don't get from eating sugar. 

The take home message here is twofold: 1) determining whether there is or isn't a real metabolic advantage to different diets is very difficult; and 2) it doesn't really matter.
Why doesn't it matter?  I'll make this simple - why should it?
Suppose Abe and Ben are identical, fat twins starting diets.  Abe is on Ornish and Ben is on Atkins.  Do you really think Abe or Ben care if one of them eats 2000 kcal/day and the other eats 2150 kcal/day and gets the same results?  No!  Most people have no idea how many kcal they're eating, nor should they.
What does matter is how sated Abe and Ben are by the food they eat.  I propose an imaginary number - the  Satiety Point, to replace the Calorie.  Food gets Satiety Points depending on how sated they make you.  If you eat meal X, and then find that you're full, and stay full for 6 hours, then meal X gets some number of Satiety Points.  If you eat meal Y and are still hungry, or you get hungry again 1/2 hour later, then it gets fewer Satiety Points.  We can argue over the exact method for measuring Satiety Points later, but I hope the idea is clear.  Now think about this: if you're a dieter, would you rather be able to eat a higher calorie meal that had fewer Satiety Points or a lower calorie meal that had more?  What actually matters to you in terms of fostering compliance with the diet?
What matters to a dieter is not how many Calories they can eat while losing weight but which method of eating can make them the most sated while maintaining weight loss.  If Abe eats 1500 kcal/day of meat and fat with a few veggies and is full all the time, never craves food, and loses 2 lb/week, while Ben eats 1800 kcal/day of high carb stuff and is hungry all the time and craving junk and also loses 2 lb/week, do you think that Ben has somehow "won" or proven his plan superior because it has a metabolic advantage?  Of course not.  Which twin is more likely to cheat over the long haul?  Which twin is more likely to be happy with his eating style?
Higher protein, high fat diets are much easier to follow, especially if you're metabolically deranged (insulin resistant).  If you're overfat, you're probably metabolically deranged.  Sorry.  I don't care, and neither should you, whether low carb diets have a metabolic advantage or not.  We should care about which diet can result in weight loss while maximizing general satiety. 
When I eat clean I'm rarely hungry, rarely crave junk food, and lose fat at a good pace.  I do it by eating moderate protein, lots of fat, and carbs from only paleolithic sources (veggies and tubers, no grains).  I don't eat a large number of calories, but what I eat satisfies me.  If I eat three slices of pizza, however, I can quickly put myself into a situation where I choke down 3000 calories in a day and am still hungry, roaming my kitchen at night looking for chocolate.  At that point, who cares about metabolic advantage? 
In the coming weeks I'll post a little bit more about nutrition, supplementation, and how I eat.  If you're training in martial arts and carrying around extra fat or not paying attention to your nutrition then you're making a mistake as fundamental as somebody who comes to class every other day but never stretches or who smokes two packs of cigarettes a day.  I'm not saying you can't get better at karate, but you're limiting yourself significantly.