Does Protein Really Help You Lose Weight? Or Gain Weight?

The latest fad in nutrition is the low-protein diet. There actually is a lot of evidence that North Americans, people in the United States in particular, eat too much protein. It just isn't true that eating too much protein is the reason people get fat. It's a little more complicated than that.

The connection between eating protein and gaining weight, and also the connection between eating protein and gaining muscle, is insulin. Insulin is the molecule that helps cells absorb sugars. It also helps muscles absorb amino acids after a workout, and regulates the release of fatty acids from fat cells to fuel muscles during exercise.

When you eat protein foods, your body makes more insulin. The scientific literature speaks of an "insulinogenic" effect of a "protein preload." All that means is that your body makes sure that the amino acids from protein foods are available to muscles that need them. If you happen to be eating high-protein foods after a workout, when your muscles are uniquely responsive to insulin so they can rebuild and reshape themselves and make themselves stronger, this response is a good thing. Insulin also locks fatty acids in fat cells so they don't interfere with the muscle's absorption of glucose from the bloodstream for making glycogen, the muscle's quick energy fuel. Glycogen is also the substance that "pumps up" muscles.

However, if you just are eating lots protein after lying around, then your muscle cells don't take up the excess amino acids. Insulin still keeps fatty acids locked in fat cells, however, and the amino acids your muscles don't use can't be stored. Your liver turns excess amino acids from protein into sugar and urea. The urea is whizzed away down the toilet, but not before your kidneys use either glutamate (which ironically, is an amino acid that appears in nearly every protein in the body) or calcium from your bones to alkalize it. It isn't your "body" that has to be alkalized. It's your urine. But the reason your kidneys alkalize your urine is to keep the pH of your bloodstream nearly constant.

So what happens when you eat too much protein?

• Your body locks fat inside fat cells.
• Your liver turns excess protein into sugar.
• Your kidneys borrow calcium from your bones to keep your body pH neither acidic nor alkaline.

If you are eating that excess protein with too many calories or too much fat (say, you're dining on fried chicken, burgers and fries, or standard American breakfast fare), then your excessive protein is contributing your weight gain. It's not utterly automatic that too much protein causes you to gain weight and have problems with insulin regulation, but in most American diets, it does.

How much protein is enough? The international standards are about 56 grams a day for adult men and about 46 grams a day for women. Those figures are grams of protein, not grams of protein food. To get those 46 to 56 grams of protein a day, you only need about 2-1/2 servings a day of animal based protein foods, about 3 oz (84 grams) per meal or a little less, or a variety of legumes, grains and vegetables totaling about 10 servings a day.

Your body isn't fussy about whether you eat animal-based foods or plant-based foods as long as you don't eat too much. Your body has an amazing ability to deal with excesses, within limits. Anything more than about 1-1/2 pounds (600 grams) of meat a day is actually toxic to your liver and kidneys, but anything more than about 5 servings of animal protein a day is setting you up to gain weight and to have problems that can lead to diabetes.

Of course, there are many other reasons to emphasize plant food sources of protein. Plants are lower on the food chain and don't concentrate environmental chemicals. Plants usually are a lower burden on the environment. They are usually less expensive. Caring about animals is a legitimate reason to eat vegetarian or vegan.

READ Pros and Cons of the Vegan Nutritional Style

The most important thing to remember about protein in your diet, however, is that you don't need more, more, more. Learn to satisfy hunger with a variety of plant foods, and you'll eat better and feel better while improving your health.

A Common Question About Plant Protein

Q. If spirulina is a source of complete protein (all the amino acids the human body needs, including the "essential" amino acids it can't make on its own), why not just get all of your protein from spirulina?

A. Spirulina is a great source of amino acids as well as most vitamins and minerals, but it is also extremely high in selenium. If you have hyperactive thyroid or Grave's disease, you should not use spirulina at all. Otherwise, you should limit your consumption of spirulina to 1 tablespoon (15 grams) per day or less.