These authors report findings of body fat loss in 37 female and 45 male overweight children, ages 10.9 + 3.5 years, during a weight reduction program and correlated the weight loss with plasma leptin levels.  The authors note that a large proportion (40-80%) of the variance in BMI can be ascribed to genetic factors; leptin appears to signal adiposity and leptin levels have not been shown to be predictive of successful weight loss. Leptin levels, although found to correlate positively with indices of general obesity, have not been found to be predictive for the success of weight loss in observational, longitudinal studies of dietary intervention.  Some studies have shown that low serum leptin at baseline is associated with greater weight loss. Others have shown, in adolescents, that a greater baseline of leptin concentration correlates with weight reduction.

In the current study, fasting plasma leptin levels were determined and subjects were stratified on their leptin Z-score into low leptin (< –2 SD), high leptin (> + 2 SD), or appropriate leptin (>–2 to < +2 SD), prior to their weight loss. Body fat was determined by BMI and skin fold thicknesses.  All subjects participated in a nutritionally balanced meal plan at 60% of the recommended energy allowances for age and sex. Physical activity was monitored, but no attempt was made to alter it.   There were no significant differences in physical activity amongst the 3 groups of children stratified by fasting plasma leptin levels.  Data was collected at 3 and 6 months which showed that 20 children had high leptin levels, 20 had relatively low leptin levels, and 42 fell in the appropriate leptin level range.   There were no statistical differences among the three groups of children at baseline.  Mean BMI and skinfold thickness at the end of 6 months were significantly lower than baseline data. BMI reduction was more evident in the subjects with adequate leptin levels but the differences were not statistically significant. Reduction in triceps and subscapular skin folds was also more pronounced in the appropriate leptin production group.  The differences in the average of these changes were statistically significant after both 3 and 6 months.

The authors suggest that children with relatively high or low leptin levels are less likely to lose body fat, as determined by skinfold thickness, during a 6 month hypocaloric diet, and that the ability to lose fat may be strictly dependent on genetic and environmental factors.  Therefore, when environmental factors are altered, those with hyper or hypo-leptinaemia are less likely to respond to those changes.

Editor’s Comment: This is an interesting and important manuscript even though some of the data do not reach statistical significance.  Researchers have been unable to show that fasting plasma leptin levels are indicators of the probable success or failure of weight-loss programs.  Recent data suggest that, in adults, lifestyle changes including weight loss, and increased physical activity can significantly reduce the risk of Type II Diabetes in high-risk adults.  The information in groups of patients who might be more amenable to weight loss programs is therefore very important.   Further studies are required in order to better understand the etiology of the differences in leptin levels in the 3 groups of children studied by del Giudice.  Confirmation of these data would be of great importance.

William L. Clarke, MD

 

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