Every time I read about protein intake as a percent of total, my hackles tend to rise. "Percent of intake" is a piss-poor way of discussing how much of this important nutrient we eat!
Suppose a calorie-dieter is taking in 600-800 calories per day, because she can't lose an OUNCE consuming more than that? Suppose she tries the WAPF recommendations of three or four times that amount of food, designed to tell her body she can afford to burn fat for fuel? "20% of calories" becomes a huge range of possibility, and yet most people would think either end of the spectrum is a reasonable amount.
I'm no expert on the subject, but I believe just to talk about grams of protein rather than percents would help the newbies significantly. They hear all sorts of conflicting advice from The Usual Suspects (TUS), like "too much protein is dangerous".... But what is too much, and according to whom?
The worst TUS out there -- our governmental bodies which promote agriculture by convincing people to load their plates with fungible commodities -- suggest a protein intake for us all which may be enough for a small child or refeeding anorexic, but I suspect to be TOO low. Body-builders traditionally favor hundreds of grams-worth of MEEEEEEAT, which may serve their immediate goals but may actually be deleterious in the long run. Reasonable sources are more likely to range from one gram per kilo of lean weight, to 1.5 g per pound of weight, depending on a lot of different variables. This sounds to me like a range we can all thrive in.
After reading Kwasniewski, I tried to aim for the g:k quantity, and had a hard time doing so! This would be about 60 g for me, and even eating only two meals a day, the meat serving at each one was very small! I still can visualize that his protein/carb balancing act can make sense, but it doesn't seem to suit my appetite and physiology. I quickly dropped back into VLC ... with a sigh of relief! I need to waste too much time with calculation, when i'm trying to stay within such a fiddly ratio!
Back when I was fully immersed in the Strong Medicine regimen, I determined that Donaldson's prescription of three 8-oz servings of fatty meat per day was just too much -- it really taxed my digestion. I reduced that to two 8-oz'ers, or three 6-oz, and everything got very comfortable. According to FitDay, my happy-zone turned out to be about 90 g protein, plus/minus 20 g per day. YMMV.
But wait -- even specifically saying "grams of protein" tends to confuse the new kids. Some people interpret this to mean protein-foods, not the nutrition info we get on the hamburger package, and they under-eat, and then complain that the diet is NOT satisfying and the hunger overwhelms them so "LC diets don't work".... [groan] THIS IS WHY YOU DON'T INVENT YOUR OWN LOW-CARB REGIMEN. You find people who try to go LC and LF at the same time, or use their 20-gram carb allowance for candy.
aside: [People who fail on a LC diet truly are NOT "doing it right." Sorry to all the people who will now accuse me of blaming the victim, but they're NOT. Low-carb diets must be tweaked for the individual, but the tweaking needs to be done by someone with a great deal of experience, maybe even a professional who has treated all kinds of patients with LC. Not your brother-in-law who effortlessly lost 100 pounds by dropping beer, bread and potatoes. Not your 22-year-old niece who lost ten when she left the cafeteria at college and started eating vegetables by the bushel. And time MUST be allowed for adaptation -- two weeks may not be enough.]
But I digress. ;-)
Some people seem to improve weight loss by raising their protein intake and lowering fat. Others, the other way around. Which YOU are will probably depend on little things like how good your body is at gluconeogenesis, how well it harvests junk proteins in autophagy, and what kinds of protein-foods you're actually eating. Your body needs protein -- full stop! HOW much it needs is individual. "High protein" to you may be "adequate protein" to me. "High protein" to me may be "adequate" to a professional athlete.
The discussion is complicated further because of the positive aspect of referring to FAT intake in terms of percentages. Objective quantity of one and subjective proportion of another require a lot of explanation! Nevertheless, it's something a lot of us like to keep in mind.
But the easiest way to START investigating how much protein is best for YOU is probably to begin with 1.5 g per kilo of your ideal weight, and listen to your body and digestion as to how satiated and fueled you feel. With time and practice, I found that I could perceive a difference in how I feel if i'm low on either protein or fat. If adding a fat-bomb to your inadequate meal doesn't satisfy you, assume that you need a little more protein.... Or if your stomach feels "overly heavy" or "bogged down" after a moderate meal, maybe you need to back off a little.
I feel very strongly about the subject of optimal protein in one's diet -- both quantity and quality! All amino acids are not created equal! :-) Eating nothing but muscle-meat is shortchanging yourself; things like good bone-broth, pork rinds (and other skin foods), and organs may be a challenge to embrace, but can do great things for your body!