Check out my protein calculator!
No matter what your diet (low-carb, low-fat, "balanced", calorie restricted, etc.) your body has a fixed requirement for protein. Eat too much and you will feel pretty sick, too little and you will lose lean body mass over time. Lean body mass is everything in your body that isn't fat or water, e.g. muscle, organs and bone. Pretty important stuff!
I discovered that I wasn't eating enough protein, even though steak is my favorite food, thanks to how I was spreading it out over the day's meals. Read all about it on my blog post, Rainy Day Protein.
The body is constantly using nutrients, e.g. fat, protein and glucose, etc. It doesn't wait until the end of the day when everything is totaled up, a deficit is noted and any shortage is made up from storage.
Instead, fat is always flowing out of your fat cells into your blood (or coming in from food) making itself available to be used and then moving back into your fat cells. Similarly glucose circulates in your blood, coming in from many sources (food, stored glycogen, gluconeogenesis) and can be restored if unused (though this is often broken in diabetics). The same is true for many micronutrients, e.g. vitamin C. So where is protein stored?
Here's the rub, there is no inert storage form of protein; it is used to build muscle, bones and organs. Your tissues are continually breaking down its protein into amino acids. From there they can either reuse those amino acids to rebuild what was just broken down, they can take even more amino acids from your blood and build more muscle or they can release those amino acids back into your blood for other organs to use. And the excess protein? It doesn't magically cause your muscles to get bigger or your bones stronger. Once your body has used as much as it needs, the rest is usually converted to glycogen (the storage form of glucose).
Conclusion: Spread out your protein over the day's meals instead of skipping breakfast and eating that giant steak for dinner.
Don't decide how much to get based on diet percentages (e.g. I eat 15% protein) and instead calculate how much protein you need to maintain your lean body mass.
The range is a starting point for you to try out. If you are doing a ketogenic diet, start at the low end. Or if you are trying to build muscle, start at the high end. From there you'll need to evaluate how that amount of protein is working for you and your goals (e.g. muscle gain, ketones, etc) and tweak from there.
I wrote a protein calculator which will figure out your protein using the formula below. If you don't know your body fat %, it will help you estimate it based on either your BMI or body measurements.
Here's an example:
So far when I've said "eat X g of protein" you've probably been thinking, "So what does that mean in terms of real food?" A gram of "meat" is not a gram of protein, since meat is a mix of protein and fat.
Ideally you should use any of the free online food databases or food tracking websites to figure out how much protein is in a food. However here are some quick ways to estimate: