By Margaret M. Furtado, MS, RD, LDN, RYT

It has been estimated that 54 million Americans are currently on a diet, and 95 percent of them have lost weight and gained all, if not more back ⁽¹⁾. The direct cost of obesity in the United States is currently approximately $39 billion per year ⁽²⁾. Americans spend $38 billion a year trying to lose weight, but without much permanent success ⁽³⁾.

According to a report in USA Today, 30 percent of Americans follow their own diet, 12 percent an MD-prescribed diet, 11 percent Weight Watchers, nine percent low-fat diet, seven percent low calorie diet, five percent South Beach diet, five percent Atkins diet and five percent sugar-free diet.

Popular weight-loss plans often contain conflicting recommendations, and seemingly healthy plans may be quite dangerous for someone with chronic kidney disease (CKD) who may need to watch potassium, phosphorus, sodium and possibly fluid intake as well.

Let’s talk first about low-carbohydrate diets, namely, the Atkins diet. The Atkins Diet, created by Robert Atkins, MD, claims a low-carbohydrate diet is the key to weight loss and good health because carbohydrates cause high insulin levels. The induction or initial diet consists of less than 20 grams of carbohydrate a day, or about the amount you’d find in a piece of fruit or slice of bread. The ongoing weight loss (OWL) phase consists of 15-40 grams of carbohydrate/day.

The initial Atkins diet plan consists of seafood, poultry, meat, eggs, cheese, vegetables, oils and butter. Later on, limited amounts of nuts, fruits, wine, beans, vegetables and whole grains are allowed. Absolute “no-no’s” consist of sweets, refined grains, milk and yogurt.

There are several concerns and unanswered questions about low-carbohydrate diets. One of the biggest concerns is the elimination of certain foods and food groups. With the strict Atkins plan, for example, you’re left with essentially just protein and fat, which cannot provide you with all of the nutrients (e.g. vitamins and minerals) your body needs for optimal health.

Carbohydrates are the best source of energy for your brain and body, especially if you’re active. Protein and fat are not as efficient, in terms of energy, since they need to be converted into a form of energy your body can use. Many people cite sluggishness and may get headaches on a low-carbohydrate diet due to this. In addition, if your kidneys aren’t working at 100 percent capacity, you want to make sure you have about half of your calories, on average, as carbohydrate to not only help with energy, but to also keep protein moderate, and in so doing, lessen the work your kidneys have to do to filter the waste products from proteins you eat, such as meat, chicken, fish and eggs.

Kidney function may be negatively affected with low-carbohydrate diets.

The kidneys are the main organs responsible for eliminating the waste products of protein breakdown. Many researchers have hypothesized that eating high amounts of protein can put excess strain on your kidneys, which may in time decrease kidney function ⁽⁵⁾. Although there is currently no proof high-protein diets cause kidney disease or poor kidney function, if your kidneys are already working less than 100 percent, maybe as a result of untreated or poorly-controlled high blood pressure or diabetes, then a high-protein diet may cause further kidney damage, and thus is not recommended.

Let’s talk about the South Beach Diet and examine its premise. This diet, by Arthur Agatston, MD, claims that switching to “good carbs” stops insulin resistance, cures cravings and causes weight loss. In addition, “good fats” protect the heart and prevent hunger. The first two weeks consist of high-protein, low-fat and extremely low carbohydrate. After two weeks, it’s a low carbohydrate plan which restricts some fruits. Allowed foods initially include seafood, chicken breast, lean meat, low-fat cheese, most vegetables, nuts and oils. Later on, you’re allowed whole grains, most fruits, low-fat milk or yogurt and beans. Foods that are off-limits include fatty meals, full-fat cheeses, refined grains, sweets, juice and potatoes.

The South Beach diet does not meet the DRI (Dietary Reference Intake) for iron and magnesium, and the author recommends a daily multivitamin

⁽⁶⁾. If your kidneys are not working at their best, I would stay away from supplements with Vitamin A, as found in many general multivitamins, since your kidney filters this vitamin, and it may become toxic, particularly since it’s fat-soluble. In addition, although iron is a mineral you may be low in, possibly because of anemia due to kidney disease, minerals like magnesium and zinc may be toxic to your kidneys.

How about Dr. Phil’s Ultimate Weight Solution plan? Is this the answer? This plan consists of three phases. The first phase, “The Rapid Start Plan,” is a low-calorie phase providing 1300 calories per day, and consists of a 14-day plan. Phase 2 provides 1100 calories, and Phase 3, 1800 calories. The plan includes seafood, poultry, meat, low-fat dairy, whole grains, most veggies and fruits, and oils in moderation. Foods excluded are fatty meats, sweets, refined grains, full-fat dairy, microwavable entrees and fried foods.

Dr. Phil’s diet does not meet the DRI for potassium, iron and magnesium, and the book does not recommend a multivitamin ⁽⁶⁾. It does, however, stress the importance of preventing dehydration, recommending 8-10 glasses of pure water a day, which is 100 percent of the RDA/AI for fluid intake. Please check with your doctor to find out what YOUR fluid goals should be to keep your kidneys as healthy as possible.

The Zone Diet, by Barry Sears, PhD, claims that eating the right mix of the right fats, carbohydrates and protein keeps you trim and healthy by lowering insulin levels. The diet is composed of 40 percent carbohydrate, 30 percent protein and 30 percent fat. The plan includes seafood, poultry, lean meats, fruit, most veggies, low-fat dairy and nuts. Only limited amounts of grains, sweets, potatoes, carrots and bananas are allowed. Excluded foods are meats, full-fat dairy products, butter and shortening. Overall, it appears healthier than the Atkins plan, with better balance and greater percentage of healthy carbohydrates and fiber, but the protein content may be too high for people with CKD.

Fat

Contrary to what you might think, you need a certain amount of fat in your diet, even if you’re trying to lose weight, since some fat is needed for the absorption of fat-soluble vitamins (A,D,E and K), as well as the production of some hormones. However, since fats have more than twice the calories of proteins and carbohydrates, most weight loss plans have limited fat. For heart health, I commonly recommend to my patients an upper limit of 30 percent of calories coming from fat to lower the risk of heart disease.

Summary

In conclusion, there are many fad diets out there today, and it’s important to be aware of potential dangers, such as the excessive protein in such plans as Atkins and Zone diets. In addition, chronic kidney disease poses unique challenges in meal planning, since traditionally healthy and recommended foods, such as beans, low-fat dairy products, whole grains and fresh fruits and vegetables may not be indicated due to high phosphorus and/or potassium contents. Fluid and salt intake may also need to be limited as time goes on. It’s vital you keep in good communication with your doctor and dietitian, and follow the meal plan they recommend for your kidney health.

Reference:

1. Consumer Reports, May 2002.

2. Researchers at the Louisiana State University Medical Center

3. According to Market Data Enterprises

4. Van Itallie, 1980.

5. Coleman MD, Serrano E. The Low-Carbohydrate Craze: Is it a healthy way to lose weight? Virginia Cooperative Extension, Virginia State University. Publication Number: 348-351, September 2004.

6. Stevens A, Dionne E, Dwyer J. Self-Help Approaches for Obesity and Eating Disorders, Chapter 2, Popular and Fad Diet Programs. The Guilford Press, New York, NY 2007.

Margaret Furtado is a registered and licensed dietitian/nutritionist with almost 20 years’ clinical experience. She is currently part of the multidisciplinary team at the Weight Center at Massachusetts General Hospital (MGH), where she counsels patients both on medical and surgical weight loss. She co-wrote the recently released book, Recipes for Life After Weight-Loss Surgery, which contains both clinical nutrition guidelines and healthy recipes for weight loss surgery patients.

This article originally appeared in the December 2007 edition of Kidney Beginnings: The Magazine.