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Reply to NJ Krilanovich

Department of Nutrition
Arizona State University
7001 E Williams Field Road
Mesa, AZ 85212
E-mail: carol.johnston{at}asu.edu

Sherrie L Tjonn

Conscious Cuisine
Scottsdale, AZ

Pamela D Swan

Department of Exercise & Wellness
Arizona State University
7001 E Williams Field Road
Mesa, AZ 85212

Heather Hutchins and Barry Sears

Inflammation Research Foundation
Marblehead, MA

Dear Sir:

We thank Krilanovich for his comments regarding our recent study (1). Low-carbohydrate diets have withstood recent scientific scrutiny (2, 3) and may soon become the "diet of choice" for effective weight loss. We challenged the view that the metabolic advantage of these diets is related to ketosis, and we showed that dietary protein (1.2 g/kg body wt) generates the metabolic milieu for efficient weight loss (1). That is, dietary protein—not ketosis or dietary fat or carbohydrate—corresponds to reduced hunger and elevated energy expenditure during active weight loss (1, 4).

The protein-sparing modified fast (PSMF) developed in the 1970s by Bistrian et al (5) permits the consumption of only lean meat, fish, and poultry at a level to provide 1.2–1.4 g protein/kg ideal body wt. Dietary carbohydrate is prohibited, dietary fat is restricted to that present in the protein source, and vitamin and mineral supplementation is necessary. Although Krilanovich agrees that ketogenic diets high in saturated fat and cholesterol (eg, the Atkins diet) may be unhealthful, he suggests that ketogenic PSMF diets would be the preferred diet for weight reduction because these diets promote "rapid weight loss and low hunger." Yet, the rate of weight loss with a PSMF diet, 1 kg/wk at energy intakes near 800–900 kcal/d (6, 7), is similar to that reported for nonketogenic, low-carbohydrate, high-protein diets (1, 8), and both diets appear to effectively control hunger (4, 8, 9).

Thus, there is no apparent advantage to restricting dietary carbohydrates to a level that is ketogenic. Vegetables and low-fat dairy products contain numerous nutrients and phytochemicals that reduce the risk of chronic disease; therefore, the restriction of these foods in the diet is simply not wise. Furthermore, a recent article provides evidence that ketosis increases blood methylglyoxal concentrations 2-fold (10). Methylglyoxal and its byproducts are considered a significant cause of blood vessel damage. We continue to claim that the use of ketogenic diets for weight loss is not warranted.

ACKNOWLEDGMENTS

SLT, the research chef, received consulting fees from the Inflammation Research Foundation. HH is an employee of Zone Labs Inc. BS is a stockholder and serves on the boards of directors of Zone Labs Inc and Zone Cuisine Inc and is also on the boards of directors of Zone Café and ZoneNet. None of the other authors had any personal or financial conflict of interest.

REFERENCES

1. Johnston CS, Tjonn SL, Swan PD, White A, Hutchins H, Sears B. Ketogenic low-carbohydrate diets have no metabolic advantage over nonketogenic low-carbohydrate diets. Am J Clin Nutr 2006;83:1055–61.[Abstract/Free Full Text]
2. Krieger JW, Sitren HS, Daniels MJ, Langkamp-Henken B. Effects of variation in protein and carbohydrate intake on body mass and composition during energy restriction: a meta-regression. Am J Clin Nutr 2006;83:260–74.[Abstract/Free Full Text]
3. Last AR, Wilson SA. Low-carbohydrate diets. Am Fam Physician 2006;73:1942–8.[Medline]
4. Johnston CS, Tjonn SL, Swan PD. High protein low-fat diets are effective for weight loss and favorably alter biomarkers in healthy adults. J Nutr 2004;134:588–91.
5. Bistrian BR, Blackburn GL, Flatt JP, Sizer J, Scrimshaw NS, Sherman M. Nitrogen metabolism and insulin requirements in obese diabetic adults on a protein-sparing modified fast. Diabetes 1976;25:494–504.[Abstract]
6. Palgi A, Read JL, Greenberg I, Hoefer MA, Bistrian BR, Blackburn GL. Multidisciplinary treatment of obesity with a protein-sparing modified fast: results in 668 outpatients. Am J Public Health 1985;75:1190–4.[Abstract/Free Full Text]
7. Stallings VA, Archibald EH, Pencharz PB, Harrison JE, Bell LE. One-year follow-up of weight, total body potassium, and total body nitrogen in obese adolescents treated with the protein-sparing modified fast. Am J Clin Nutr 1988;48:91–4.[Abstract/Free Full Text]
8. Pereira MA, Swain J, Goldfine AB, Rifai N, Ludwig DS. Effects of a low-glycemic-load diet on resting energy expenditure and heart disease risk factors during weight loss. JAMA 2004;292:2482–90.[Abstract/Free Full Text]
9. Wadden TA, Stunkard AJ, Day SC, Gould RA, Rubin CJ. Less food, less hunger: reports of appetite and symptoms in a controlled study of a protein-sparing modified fast. Int J Obes 1987;11:239–49.[Medline]
10. Beisswenger BG, Delucia EM, Lapoint N, Sanford RJ, Beisswenger PJ. Ketosis leads to increased methylglyoxal production on the Atkins diet. Ann N Y Acad Sci 2005;1043:201–10.[Abstract/Free Full Text]

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