skibum1981, if you are looking for a scientific explanation, try the following Wikipedia link:

This is a link

It appears a lot of research has been done on this subject to determine the ratios and how they affect body chemistry. I think the best us non-PHD types can do is accept that the ratios spelled out in the P90X nutrition guide are going to affect the average person in a fairly similar way and start there.

I think the ratios are overrated a bit, and your calorie total is the most important thing. With that being said, I think it's just important to have some kind of balance in your diet. You wouldn't want a diet that was all carbs for example.

You're right; a person whose calorie maintenance is 2000 calories a day could eat 1500 calories of garbage and still lose weight. The same person could also eat 1500 calories of nutritious food, however, and he or she would be much healthier.

I had a similar question and stumbled on this (lengthy) discussion. Basically, the guy is making the same statement that you are making, that a calorie is a calorie. In the end, he does change his mind. I found it to be a really great discussion and very informative. You do have to get past all of the stupid internet discussion name calling and such.

This should keep you busy for a few hours.

www.board.crossfit.com/showthread.php?t=...5&highlight=diet

i'm sure some of what i'm about to say has already been said, so i apologize.

here's the thing. if you're speaking STRICTLY about WEIGHT LOSS, yes, a calorie is a calorie, if you have no concern WHATSOEVER about body composition, and how you look, but just the number on the scale, yes, you will lose weight on 1500 calories of twinkies. you'll be unhealthy, malnurished and feel like crap. but you'll lose weight!

Proteins, Carbs and fats perform different functions when ingested. Steve Edwards (i forget if it was on his blog or a beachbody newsletter) goes into some detail on why we need each. if i find the link, i'll share it. but i'll try to hit on the main points:

Carbs are for energy, and your body's primary source of energy, plain and simple. any unused carbs will be converted into body fat and stored, because your body can't store unused carbs in that form. this is where the ratios is important, if you're worried about body fat. eat the carbs but dont burn it off? well, it becomes fat.

Protein is kinda universal, but is mainly used to repair your muscles. it can also be converted into energy, but requires a lot from your body to do so. keep in mind also, that about 20% of the calories from protein, is used to digest itself, so if you eat 100 calories of protein, it's really 80 calories, if you consider its thermal effect on your body.

Fats are the least needed from your body, and can also be used as energy. But it is also essential to have the good fats, like, omega 3. i dont remember the details, but fats assist in many of your daily bodily functions. Fats are also the slowest digesting, which is why its recommended to have, if you're going to have a fast acting carb, to add some good fats to, to slow down the fast acting nature of that carb, preventing a spike in your insulin, which is what ultimately makes you fat.

hope i made sense there, and if anything i've said is incorrect, please, let me know!

ah, here you go. a little long, but a worthwhile read:
http://www.beachbody.com/product/newsletters/344.do#article2

Thanks Ben90X. One point of clarification though -- your body can store carbs, and indeed does, as glycogen. However, it can only store a limited amount. And I think only complex carbs can be stored, but I'm not sure on that.

But yes, what you said made sense. All of this discussion has really made me understand that while the macronutrient ratios are quite a bit overrated, we still need totally revised nutrition labels.

In particular, calories for carbs is quite misleading. "Effective" calories from carbs should be reported, as dietary fibers are pretty much meaningless in terms of what gets turned into fat, though a naive approach would say it's 4 calories per gram nevertheless, and sugar alcohols count about half as much as simple carbs. Plus, complex carbs shouldn't be grouped the same as simple carbs (HFCS, sugars, fruit, etc.).

Additionally, it seems the same is true for proteins as well. There should be a new calorie number reported -- "effective calories" or something like that.

It'd be nice to know how many calories you're REALLY consuming ... i.e., once you account for what percentage of the calories are converted to energy ... this seems like the most important statistic. Amazingly, even on dailyburn and myplate, at least without paying an extra fee, you don't have access to this information...