Volume 20, Issue 1, March 2004

Table of Contents 20-1

Low-Carbohydrate Diet, Weight Loss and Cardiovascular Risk

Sondike SB, et al. Effects of low-carbohydrate diet on weight loss and cardiovascular risk factors in overweight adolescents. J Pediatr 2003;142:253-258.

Abstract

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The prevalence of childhood obesity continues to rise to epidemic proportions, with adolescents beginning to show significant signs of developing cardiovascular risk factors. A variety of weight-loss diets have been tested in adult populations, but the assessment of these diets in children, especially those with decreased carbohydrate (CHO) or fat remains limited. Sondike and colleagues report on the use of a low carbohydrate (LC) versus a low fat (LF) diet in a group of adolescents (ages 12-18) with a BMI > 95 th percentile. Thirty-nine adolescents participated in the 12-week randomized controlled study. The LC diet consisted of a daily CHO intake of <20g/d for the initial 2 weeks and then up to 40g/d. There were no restrictions on protein, fat or calories. The control group was assigned to a LF diet (< 30% energy from fat, <40g/d) with 5 servings of starch (15g CHO each serving) daily. There were no restrictions on calories. Thirty minutes of exercise 3 times a week was encouraged, but not monitored. Subjects were weighed every 2 weeks and dietary adherence was monitored at those visits by a dietitian who reviewed 3-day food records. Lipid profiles including fasting total cholesterol, triglycerides, LDL cholesterol and HDL cholesterol were measured along with electrolytes and liver function studies at baseline and at 12 weeks. Ketonuria was monitored and recorded by the subjects daily.

Thirty subjects completed the study (LC = 16, LF = 14). Subjects in the LC group lost significantly more weight than those in the LF group ( 9.9 + 9.3kg vs 4.1 + 4.9kg, p<0.04) despite having consumed more daily average calories (1830 + 615 vs 1100 + 297, p<0.03). BMI improvement was significantly greater in the LC vs LF group as well (p<0.05). LF group subjects had significantly lower LDL cholesterol levels at 12 weeks than at baseline, whereas there was no change in these levels in the LC group. HDL cholesterol rose significantly in both groups and triglycerides fell significantly in the LC group. The authors state that their results were consistent with those from previous weight-loss studies employing strict calorie control (protein-sparing modified fasts). Their de-emphasis on calorie control may reduce the concern for the effects of dieting on linear growth velocity. The authors also suggest that the LC diet may not be appropriate for adolescents with significant baseline elevations in LDL cholesterol. The palatability of the LC diet may be one reason that 8 of the LC subjects voluntarily remained on the diet for a year.

First Editor's Comment: This is an important study and hopefully it is but the first in a series of weight-loss studies designed to improve fitness and cardiovascular risk among obese children. The authors refrained from overstating their findings. As pointed out in an accompanying editorial by Daniels,1 the long-term effects of LC diets on bone density, body composition, insulin resistance, and glucose metabolism remain to be defined. Sondike and colleagues do not, and because of the short 12-week duration of their study, could not address these issues. But these will need to be addressed, as will the metabolic and pathophysiologic abnormalities associated with obesity; none of these are trivial. It is anticipated that pieces of this complex "bio-psycho-behavioral" disorder will become more evident over the next few years as more and more investigators begin to study obesity and develop effective treatment regimens.

William L. Clarke, MD

Second Editor's Comment: The first low-carbohydrate diet for weight loss was described in 18632 and was popularized by Dr. Atkins3,4 in the modern era. However, the efficacy and safety of such diets are still being debated. A systematic review of 107 articles recently concluded that there is insufficient evidence to make recommendations for or against its use.5 The first randomized trial conducted for up to 12 months of such dietary therapy showed that LC diets initially induced more weight loss than the low-calorie high-carbohydrate LF diets. However at the end of one year the differences were no longer evident.6 Differences in weight loss were principally associated with energy intake. 7 A calorie is a calorie no matter its source.

Fima Lifshitz , MD

References - (linked to )

1. Daniels SR. J Pedatr 2003:142:225-227.
2. Banting W. Letter in Correspondence. Harrisions and Sons. 1863.
3. Atkins RC. Dr. Atkins' Diet Revolution. David McKay, New York , 1972.
4. Atkins RC. Dr. Atkins' New Diet Revolution. M Evans , New York , 2001.
5. Bravata DM, et al. JAMA 2003;289:1837-1850.
6. Foster GD, et al. N Eng J Med 2003;348:2082-2090.
7. Samantha FF, et al. N Eng J Med 2003;348:2074-2081.

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