People don't need nearly as much protein as most Americans eat. One thing I've noted again and again during my decade-long stay in Asia is how much more protein westerners (and especially Americans) eat than people here. And interestingly, the US response to obesity has been to go for even more protein.
To people who make rice the staple of nearly every meal, it looks insane.
Your body doesn't store protein. Amino acid (or gluconeogenesis) demands which cannot be fulfilled by dietary intake (what you've recently eaten and/or is passing through your digestive tract) are satisfied by catabolizing existing body tissues: skeletal muscle, and eventually, organs.
Over time, this adds up. Sarcopenia is age-related muscle loss, which amounts to 0.5%-1% of muscle mass per year. It's reversible through strength training and proper nutrition.
While this doesn't require eating hundreds of grams of protein per day (though strength athletes may eat, and benefit from, such quantities), ensuring that your protein intake is spread throughout the day is helpful.
Rice is interesting in that, while a carbohydrate, the insulin response to it differs from that of wheat and sugar. That and total dietary intake largely account for the lower prevalence of obesity among traditional Asian diets.
The Standard American Diet has a lot to condemn it. While it can be high in protein, it's generally higher in processed carbs, trans fats, and questionably raised and prepared proteins (CAFO / feedlot / factory-raised meats, with beef highly treated with hormones and antibiotics).
Among the fitness geeks I know, the first response to those looking to drop fat is to vastly increase the intake of green/colored/leafy/cruciferous vegetables. Just sayin'.
Protein intake? 0.5g - 1.25g per pound lean body mass, for general public through advanced strength/cardio athlete. The catabolic effects of long-duration cardio may require more protein even than strength training, ironically.
>"The catabolic effects of long-duration cardio may require more protein even than strength training, ironically."
That's not what the data suggests.
Elite Kenyan marathoner's diets are approximately 10% protein (or 75g per day), 75% carbohydrates and 15% fat. Corn is the primary energy source. Non-Kenyan runners who have adopted a similar diet have done so with excellent results.
It's not that protein is a primary fuel source for muscle, but that excessive long-duration cardio actively breaks down muscle tissue. I'm familiar mostly with empirical evidence: long-duration ocean rowers (60-180+ days of 8+ hours/day rowing) typically lose 30-40# of body mass, much of that lean tissue.
Elite Kenyan marathoners aren't particularly known for being heavily muscled. Elite sprinters, on the other hand, typically are.
I could dig for some more rigorous research, no time presently.
My original (and still current) point is that protein is an essential macronutrient and that in the interest of general fitness, people should consume it fairly constantly throughout the day, at roughly 0.5 - 1.25 g/lb body mass.
A champion Kenyan marathoner, say, Geoffrey Mutai, weighs roughly 53 kg (123 lb) at 182 cm (6 ft). If he's representative of the Kenyans consuming 75g of protein per day, he actually illustrates my points fairly well:
1. He's consuming 0.6g protein per pound body mass. Which is in the range I'd suggested for general health.
2. I'd suggested that athletes engaged in long-duration cardio should eat more protein, or suffer catabolic effects. Mr. Mutai exhibits the second part of that statement. While it's an absolutely horrid measure of anything resembling health, BMI gives us at least a scale to compare relative body mass to height ratios. Mutai's clocks in at 16.6, where "normal" is generally given as 18.5-25, and a bodybuilder, at 3-6% bodyfat, may clock in at 30-40. The argument here isn't fitness or appropriateness to task, it's to point out that our Kenyan here is at the very low end of the body mass-to-height scale, as a consequence of having both exceptionally low bodyfat, and very little muscle.
3. The unanswered question and unstated assertion is how this affects longevity and quality of live, and that we're discussing snacking habits, nutrition, and exercise in the context of general fitness in a general population that's not, as a rule, prone to trotting off for 26.21875 mile jaunts on a daily basis, though some may partake occasionally. Longevity of athletes is a mixed bag: American football players pretty notoriously die young (55 or so median). Finnish Olympians, according to one study, showed a few added years of longevity. The Stanford Runners Study (long-term longitudinal research) shows very consistent benefits of regular exercise, though I believe this is generally not inclusive of daily marathon-distance bouts. I'm not aware of the specifics of Mutai's training, but suspect much of it takes place at sub-marathon distances as well.
There's also the matter that extreme devotion to a single mode of exercise can lead to other problems. Long-distance cyclists, it turns out, suffer from both muscular and skeletal weaknesses due to the specifics of muscle stimulus, bone loading (or lack), and biochemical changes induced by hours spent on a bike. They're now encourage to strength train to make up for this, though it's another sport that rewards a light, wiry frame.
And finally, yes, if your goal is to be very, very good at winning marathons, you want to be tall, light, slow-twitch, very efficient at metabolizing glycogen, and very good at metabolizing fats (former for higher output, latter as lipid metabolism is generally rate-limited). In a fitness-for-goals perspective, Mr. Mutai is precisely where he needs to be.
For the average Joe or Jane, perhaps not so much.
These, and the sharp bit at the end, are my points.
> To people who make rice the staple of nearly every meal
Even if you're eating brown rice exclusively, that's still terrible for you from a health standpoint. The glycemic index alone greatly advises against it.
Yoghurt and cottage cheese are go-tos for me. Jerky. Some fruit, more veggies. Definitely nuts.
And lots and lots of water & tea.