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One-size-fits-all weight loss diets are the rage. The two biggest are high carbohydrate diets and high protein diets. These diets have nutritional weaknesses that people following them should understand. This column addresses high carbohydrate diets. Our next column will discuss high protein diets. High-carb diet
may cause harmProblems with the one-size-fits-all approach are similar to problems with some public health recommendations. Both address problems that affect many people and recommend solutions that benefit many, but not all, people. Both can be detrimental to some individuals and even cause death.
For example, iron is added to enriched flour to help prevent iron deficiency anemia in the general population. Some individuals are unaware that they are genetically prone to accumulate too much iron.
When they regularly consume iron-enriched flour products or other iron sources, it can cause a disease that damages tissues such as liver, heart and blood vessels.
High carbohydrate diets are effective for weight loss primarily because they are low in fat and high in fiber. You can eat a greater volume of food without too many calories. They also are relatively low in protein. People lose weight because they aren't used to eating such a large volume of food.
Individuals require a certain amount of protein per day to maintain body protein in muscle and organ tissues and to produce appropriate amounts of hormones and enzymes. Muscle is constantly turning over and replacing itself as long as there is adequate protein.
Decreasing calorie intake to lose weight does not decrease a person's need for protein. A rule of thumb is about 0.4 grams of protein is needed per day for each pound of body weight. A 100 pound person should consume about 40 grams of protein per day.
High carbohydrate diets may contain adequate protein when a person is consuming more than 2,000 calories a day. However someone eating only 1,200 calories per day is probably not getting enough protein. Long-term inadequate dietary protein will cause the blood to contain less of the protein albumin. Albumin helps maintain normal blood volume by holding water in the blood vessels. When individuals have too little albumin in their blood, they urinate more often, causing them to awaken frequently at night. Decreased blood volume also can cause increased blood pressure.
Another important problem associated with low dietary protein is that the required protein turnover will cause muscle wasting and weakness. Remember, the heart is a muscle. Some heart rhythm problems may be associated with inadequate dietary protein.
Two other nutrients can be marginal in high carbohydrate diets: calcium and essential fatty acids. Many plant foods contain compounds that bind to calcium in foods and make it unavailable to the body. The long-term result is an increased risk of osteoporosis. Essential fatty acids are needed to produce prostaglandins which help the body maintain normal blood pressure.
Whereas deficient calcium and essential fatty acid intake can take years or decades to become serious problems, inadequate protein intake can cause problems within weeks or months, especially in elderly people. Dietary variety and a balance of all nutrients is essential for long-term health.
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Alan Titchenal, Ph.D., C.N.S., is a sports nutritionalist in the
Department of Food Service and Human Nutrition,
University of Hawaii-Manoa.Joannie Dobbs, Ph.D., C.N.S., is a food and nutrition consultant
and owner of Exploring New Concepts, a nutritional consulting firm.
She is also responsible for the nutritional analyses indicated
by an asterisks in this section.