K. Harris:

"Once your individual resting metabolic rate is determined, one can easily determine the amount of calories needed to sustain, gain, or lose body weight, based on gender, height, weight, age, and activity level."

No.

"ERS data suggest that average daily calorie intake increased by 24.5 percent, or about 530 calories, between 1970 and 2000." (Source: USDA)  

Assuming that people were close to maintenance in 1970, "calorie math", which gives us the 3500 calories per pound of fat rule, would mean that all Americans in 2000 were gaining one pound of fat per week indefinitely! 

Yes, we're getting fatter…but the average adult American in 2000 was only ~19 pounds heavier than the average American in 1970. (Source: CDC)  That's a long way from the one pound per week predicted by the calorie model!  

In fact, "calorie math" says a 19-pound gain in 30 years should require a surplus of only 6.07 calories per day.  That's nearly two orders of magnitude from the observed 530 calories per day.

"A calorie is a calorie; it is the human metabolic rate that's not just a human metabolic rate that is the changing factor."

But what is this mysterious "metabolic rate"?  All you've done is moved all the magic from one place to another.  

Furthermore, attempting to explain all the observed differences between diets in terms of magical adjustments to "metabolic rate" makes it difficult to explain why 1800 calories of grass-finished beef, pastured eggs, kale, and sweet potatoes don't have the same effect on your body (or your bodyweight) as 1800 calories of Coca-Cola.

The answer, of course, is that "metabolic rate" is driven in large part by your food choices, whether short-term (e.g. thermogenesis) or long-term (e.g. metabolic flexibility).

"Bodybuilders have been counting calories for years and can predict their weight and bodyfat % pretty much down to the day of competition."

No.

I have some experience with bodybuilders and nationally competitive weight-class athletes.  As Beowulf pointed out, they are strongly concerned with both macronutrients and supplements, not just calories, because they dramatically affect your body's hormonal and metabolic state.  

No competitive weight-class athlete, whose livelihood depends on their ability to make weight, ever says "My diet says I can eat 1100 calories a day until the competition…I'll take that as two slices of pizza, two ice cream sandwiches, and a Coke."  

Short version: Beowulf's explanation in #60 is correct.  

E Craig:

See Beowulf's explanation in #60.

Alex:

If you're eating roughly the same foods after you start "calorie counting" than you were before, you're maintaining a similar level of activity, and you're not trying to restrict "calories" too dramatically, then yes, you might see reasonable results.

Why?

Because by not changing the composition of the food you're eating or your activity level, you're likely maintaining a very similar hormonal and metabolic environment.  All you're doing is eating less of the same food you were before.  Result: if you don't kick your body into starvation mode (i.e. you're not already strongly weight-reduced and you're not restricting your food intake too greatly), you'll probably lose some weight.

Andy:

That explains the appx. 300 calorie difference in REE+TEE between high-protein, low-carb diets and others, then.

(Article, paper by Ludwig et.al.)

Jen W:

Going by physical dimensions rather than weight is an excellent idea, and one I recommend to all.

My point is that "calorie counting" is, at best, an approximation to what's really happening — and treating food as a generic substance made out of interchangeable "calories" can lead us to make bad decisions that will actively sabotage our health.

Beowulf:

Exactly true.  Anyone who thinks bodybuilders (or any weight-class athlete) only counts "calories" can't possibly have any real-world experience with competitive weight-class athletes.

Finally…I'm caught up!  Thanks, everyone, for your patience and interesting questions.

JS

Steven:

That depends on how intense your training is.  For instance, Olympic weightlifters have been measured in negative protein balance (i.e. not getting enough) at 2 g/kg/day.  1 gram per pound per day is the usual "round number" starting point for active people.

I find that so long as I'm not camouflaging protein by eating it as protein shakes, my own satiation is an excellent guide.  Lean protein becomes extremely unappetizing once you've eaten enough!

As far as "muscle-building proteins", all complete proteins (which includes basically most animal-source proteins) will help build muscle.  The main difference between whey, casein, and a steak is how quickly they're digested absorbed.  Whey is absorbed very quickly, so immediately PWO is probably a good time for a scoop...but at most other times (e.g. before bed), you'll want something that is digested and absorbed more slowly, e.g. a steak.

AFAIK.  Sports nutrition is a complicated field that I don't claim to understand fully -- and many of the people making bold claims for their own plans aren't substantiating them nearly as well as they claim!

Heather:

"I know my choice…"

It's difficult for most people to gain fat on clean, Whole 30-style paleo: most people who do are eating/drinking dairy products or cheating in some other way.  (Though not everyone...some people do need to stay in ketosis or have other special dietary needs.)

Note that there's an important difference between weight loss stalls ("I'm not losing three pounds a week OMG what's wrong HELP) and actually gaining weight.  As I've said many times, it took decades to break yourself: don't expect to fix yourself in a month or two.

Eddie:

When asking how to gain muscle mass, absolutely listen to bodybuilders, powerlifters, and other strength athletes!  Their theories may not be entirely correct, nor their approaches optimal, but they have the salutary characteristic that they actually work in the real world...

...as opposed to untested hypotheses usually based on one or two in vitro experiments and knockout mouse studies, by people who don't have much muscle mass and don't lift heavy weights.

Dana:

Addressing starvation is beyond the scope of this article, but AFAIK your understandings are correct.  Kwashiorkor and other protein-deficiency malnutrition syndromes are disturbingly common, whereas rabbit starvation is mostly a historical footnote for a few explorers.

JS