How important is Protein?

Protein is one of the three pillars of the Zone Diet—or any diet (along with carbohydrates and fat). Dr. Barry Sears determined that adults need a very specific amount of protein tailored to a person’s size and activity level, in order to sustain their lean body mass.

When the Zone Diet first emerged onto the public stage in 1995, people were calling it a high-protein diet. In fact, Dr. Sears warned against high-protein diets. If you were to judge by the government standards, Dr. Sears’ diet would certainly seem to be an excessive-protein diet, but more and more medical opinions are coming into agreement that we must have quite a bit more protein than our not-so-brilliant government has set as the RDA.

The RDA suggests 0.8 grams of protein per kilogram of body weight. For a woman who weighs 130 pounds (59k), that would translate to about 47 grams of protein per day. Dr. Sears recommends that any size woman will require 77 grams of protein a day just to maintain her lean body mass. After that, he has a formula, as well, that takes activity level under consideration, along with weight, height, and some specific measurements. Originally, he used the formula for everyone, and some found their protein prescription to be less than 77 grams, but he quickly learned that we lose muscle with less than that, no matter our size or activity level.

Children need more protein per pound of body weight than adults, due to the continual growth of bones, muscles, and tissue.

Here’s a balanced and thoughtful view from Harvard’s Health Blog by someone not trying to sell you a book or prepared diet meals, or a week on an expensive cruise: That isn’t to say that those with a financial interest are trying to mislead you—only that it’s good to get more opinions.

Note that in the article linked above, it is mentioned that eating your protein requirement throughout the day—some at every meal—is preferable to having a heavy dinner and trying to get all your protein at once. Think of your food like an IV drip you get in the hospital, delivering nutrients to you throughout the day. In the Zone Diet you would balance your protein, carbs, and fats at every meal and snack for the best possible hormonal response and you would eat every 4-6 hours except when sleeping.

This post is about protein, however, so let’s consider why eating adequate protein is important.

  • Protein builds muscle.
  • Protein intake supports healthy connective tissue that is made up of fibrous proteins. Collagens are also proteins.
  • Protein is necessary for cellular function. Dietary protein is necessary for cellular repair and for the body to make new cells (which helps recovery after an injury).
  • Protein provides amino acids, many of which our bodies cannot manufacture.
  • Protein provides energy calories.
  • Protein slows the rate of carbohydrates/sugar into the bloodstream aiding in blood sugar control.
  • Protein supports healthy hair and nail growth.
  • Proteins aid in the production of hormones.
  • Proteins provide immune system support by forming antibodies.
  • Your body burns protein when your diet is too low in fat and carbohydrates (which is why high protein diets can cause muscle loss).
  • Your body does not store protein for a rainy day; it has to come by way of food, regularly.
  • Some research has shown that high-protein diets can lower blood pressure
  • New research shows a relationship between high-protein diets and a lower risk of developing Alzheimer’s disease (
  • “Protein from animal sources during late pregnancy is believed to have an important role in infants born with normal body weights.”

You cannot get all the essential amino acids from single plant foods so you have to organize your diet with different sources of plant proteins throughout the day if you are vegan. Soy may provide all of the amino acids, if not in the same quantity and balance as animal protein. Animal proteins, on the other hand, have all the essential amino acids in better balance to give your body the tools it needs for healthy functioning. One of the problems with using soy as a primary source of protein is that it takes so much. To get the same amount of protein from soy as from 3 ounces of chicken, you’d have to consume about 8 or 9 ounces of firm tofu. If you just love tofu, that may work for you.

Quinoa is a wonderful plant food with a fair amount of protein. One cup contains over 8 grams of protein. However, in that same cup of quinoa, you’ll also get a whopping 34 grams of carbohydrates (when adjusted for fiber content). That means, in Zone Diet terms, that you are getting a little more than one serving of protein to almost four servings of carbohydrates. If you rely on this kind of formula for your daily eating, you probably will gain weight.

One concern with relying on beans and nuts for your protein is the digestibility of all the protein in that food. Some of it is bound up in fiber and isn’t absorbed by the body so it’s important to take that into account.

If you are a vegan and concerned about your protein, here is a good article with a pro-vegetable point of view:

I’d be delighted to live on plant foods and if my goal was for 45 grams of protein per day, it might be doable. But my goal is 77 grams and the amount of plant food it would take to provide that much protein is overwhelming to me. Also, it takes an enthusiastic cook to prepare a healthy plant diet and once I emerged from those days on the farm of churning butter and making bread, I have spent as little time in the kitchen as possible.

Just to give you an idea of what 77 grams of protein looks like for the average, non-athletic woman, it could look like this:

  • 3 eggs for breakfast (21 grams)
  • 3 ounces of chicken for lunch (21 grams)
  • 5 ounces of fish for dinner (21 grams)
  • 1 ounce of cheese for a snack (7 grams)
  • ½ of a protein bar for another snack (7 grams)

Of course, you would be eating fruits, vegetables and a little good fat along with that protein. If you are not a big person, 3 ounces of chicken is about the size of the palm of your hand. It’s really not a lot. I have female friends who can eat 12 ounces of steak at a single meal, which is 84 grams of protein. At a single meal. Seventy-seven grams might seem like a lot, however, if you are at the other end of the spectrum and don’t eat any animal foods, even though the volume of plant foods would be much greater for the same protein benefit.

Will you lose lean body mass if you don’t eat enough protein? It’s easy enough to determine for yourself. Let’s say you need to lose ten pounds. Get your LBM estimate from the Zone Body Fat Calculator ( before you embark on another diet of your choice, and when you’ve lost 5 pounds, or all ten, measure again and see if you are losing LBM or just fat. If you are losing LBM, you need more protein. Maybe you aren’t even losing weight and don’t need to. Measure now and compare it to a new measurement several months in the future. It’s easy to find out if you are providing your body with the building blocks it needs to stay strong.