The Lowdown On High Protein Diets|
By Cynthia Sass, MA, RD
While dining at a favorite restaurant recently, I overheard the woman at the next table explaining her miraculous new weight loss program to her companion. She was pleased with her recent weight loss, but she was miffed about what to order from the menu. She explained, "I can eat chicken but not the rice, no bread, but cheese is OK. I wonder if I can ask them to substitute more meat for the vegetables." Her companion was shocked. "More meat and cheese? I thought carbohydrates were the way to go. Now it sounds like those are out again. I never know what to eat anymore."
It seems like this is a common scenario wherever I go. When people find out I am a nutrition professional, they often ask, "What do you think about the new high protein diets?" My first response is, high protein diets are nothing new. As a child, I remember my mother and older sister devouring cans of tuna and hard-boiled eggs while refusing pasta, breads and fruits. Fad diets cycle in and out of popular culture, as do fashions.
High protein diets seem to be this year's rage among those attempting to lose weight and even among athletes seeking optimal performance. Movie stars, models, celebrities, trainers, even some doctors tout the benefits of protein, but when it comes to science, are high protein diets savvy or unsound?
HOW DOES THE BODY USE FOOD AS FUEL?
In order to evaluate dietary recommendations, we must first understand how the body works. Calories, or energy are the body's fuels, like gasoline in your car. Food calories come in the form of carbohydrates, proteins and fats. Carbohydrates are the body's preferred energy source. Every cell in the body, particularly the brain, uses carbohydrates as fuel. Your body has the capacity to store some carbohydrates in your liver and muscles in the form of glycogen. Glycogen is often called the 'storage form' of carbohydrates. This glycogen is broken down and used by the muscles and the brain when energy is needed between meals. This extra supply of glycogen is stored with water. About 3 grams of water are stored with every gram of glycogen.
Protein and fat calories also supply energy to the body. These two fuels have very specific jobs. Proteins help to maintain the body's immune system, form enzymes, hormones and other metabolic necessities. Fats are necessary to maintain the nervous system, cell membranes, hormones, absorb fat-soluble vitamins and aid in metabolism.
HOW CALORIE INTAKE INFLUENCES METABOLISM
Total calorie input often determines how these fuels are used within the body. Your calorie needs are determined by your body's metabolism, or metabolic rate. Metabolism is roughly the number of calories the body needs to maintain itself each day. This number is influenced by factors such as age, gender, muscle mass and activity level. A typical calorie need may be 2,000 per day.
Let us assume that Joe's calorie input from food is close to his calorie needs, or metabolism. If this is so, Joe's body will have enough energy to maintain itself. We know from nutrition research that about 15% of Joe's calorie needs should be provided by protein in order to meet his protein needs. About 25% of his calories will meet his body's need for fat. The remainder of the calories, about 60% should come from carbohydrates. These carbohydrates will provide energy to his brain and cells and supply enough excess carbohydrate to be stored in his liver and muscles as glycogen for later use between meals.
Recently, carbohydrates have received a reputation for causing weight gain and even diseases. Some low carbohydrate diets mention the effects of carbohydrates on blood levels of insulin and eicosaniods. Insulin does indeed cause excess carbohydrates to be stored as fat, but only when one consumes more calories than the body needs. This is a common myth associated with carbohydrates. Carbohydrates themselves do not cause weight gain.
Rather, the excess calories, which are not needed by the body, are stored as bodily fat with the help of insulin. In fact, excess calories in any form, even proteins, are converted to fat. Even a pure protein diet will cause weight gain if more calories are consumed than the body can use. The eicosaniods discussed in some high protein diet books have not been found to promote disease in any published research.
EFFECTS OF HIGH PROTEIN DIETS
If Joe alters his diet to become high protein, low carbohydrate, several alterations will take place. First, he will probably be consuming fewer calories. Most high protein diets are low calorie diets. Because his diet is higher in protein and fat, Joe feels fuller and eats fewer calories per day.
Whenever one consumes fewer calories than the body needs, weight loss occurs, regardless of the diet composition. Instead of using protein and fat to promote fullness, Joe could increase his intake of fiber from whole grains and legumes to produce the same effect.
Second, Joe's low carbohydrate diet will not allow his body to maintain its stores of glycogen in his liver and muscles. This glycogen is stored with water. Thus Joe will lose weight as a result of this loss of glycogen and water from his body.
Third, Joe is not providing his body with enough carbohydrate to supply his energy needs. The excess protein and fat he is eating must therefore do carbohydrate's job of providing energy to the brain and cells. When excess proteins and fats are consumed, the liver and kidneys have more work to do. Protein contains nitrogen, a waste product not found in carbohydrates.
Nitrogen must be separated from the protein molecule and processed by the liver. The kidneys must then filter the excess nitrogen out of the body. The more protein Joe eats the harder his liver and kidneys must work to accomplish this task.
When fats do carbohydrate's job, ketones may be produced. Ketones must also be processed and excreted by the liver and kidneys to prevent ketosis, a potentially fatal condition in which the body becomes too acidic. Because Joe's kidneys must filter out the excess nitrogen and ketones, he may become dehydrated, leading to further weight loss. In a dehydrated state, Joe's body may not be able to maintain its temperature properly, making him more susceptible to heat exhaustion or heat stroke.
Lastly, because Joe is eating more protein, his intake of fat, cholesterol and saturated fat will likely be high. The American Heart Association recommends an intake of no more than 300 mg of dietary cholesterol per day. Just one 3.5 ounce piece of white meat chicken without skin, roasted contains 77 mg of cholesterol, one quarter of the daily limit. One 3.5 ounce portion of extra lean ground beef, baked to well done contains 107 mg of cholesterol. Diets providing 16 ounces of lean meat and 4 ounces of cheese per day can provide almost double the amount of dietary cholesterol recommended by the American Heart Association daily.
Avoiding carbohydrates may also compromise intakes of dietary fiber. The American Institute for Cancer Research recommends the consumption of a diet high in whole grains, cereals, legumes, fruits and vegetables and limited in animal foods. The Dietary Guidelines for Americans recommends consuming a diet with plenty of grains, vegetables and fruits and only 2-3 servings of meat or meat substitutes per day.
In fact, several of the most well known and credible health organizations do not advocate high protein diets. These include The American College of Sports Medicine, The American Dietetic Association, the Women's Sports Foundation and the Cooper Institute for Aerobics Research.
The bottom line on high protein diets:
COMMON QUESTIONS ABOUT HIGH PROTEIN DIETS
Q. If high protein diets are not healthy, why do so many trainers and even doctors recommend them?
A. It is not natural to assume that all medical or health professionals have a good nutrition background. Nutrition is a complex specialty and can be studied briefly or extensively. An extensive knowledge of nutrition is necessary in order to evaluate dietary recommendations. Trainers and physicians may have taken a few courses in nutrition or even none at all. Registered Dietitians or R.D.'s are nutrition experts who have completed a minimum of a bachelor or masters degree in nutrition, a 900-hour clinical internship, and passed a national credentialing examination. They are required to maintain continuing education in nutrition and are governed by the American Dietetic Association.
Q. If I can lose weight on a high protein diet, shouldn't I do so for my health?
A. No. Don't forget the big picture. Reducing weight is important for health, but not at the expense of your overall well being. Preventing heart disease, diabetes and cancers through increasing dietary fiber, eating plenty of fruits and vegetables, becoming physically active and reducing fats and cholesterol is just as important. You can easily lose weight on a high carbohydrate, high fiber diet if you eat sensible portions and maintain physical activity.
Q. If high protein diets are not healthy, why do they receive so much attention in the media?
A. For decades, people have been looking for a magic bullet to cure obesity and chronic disease. Most Americans know that the keys to weight maintenance and disease prevention are balanced nutrition and physical activity. Yet, most of us struggle with achieving this lifestyle. Fad diets provide the illusion of a quick fix. They are a much easier alternative to making lifestyle changes. New and controversial diets will always receive media attention, whether sound or senseless.
ABOUT THE AUTHOR
Cynthia Sass is a Registered Dietitian with a B.S. in dietetics and an M.A. in Nutrition Science from Syracuse University. She is a member of several professional practice groups, including SCAN, (Sports, Cardiovascular and Wellness Nutritionists). She also had Personal Trainer certification with the Cooper Institute for Aerobics Research.