Tehran University of Medical Sciences Journal of Nutritional Sciences and Dietetics 1 2 2015 10 05 86 92 EN Kurosh Djafarian Division of Obesity and Metabolic Health, Rowett Institute of Nutrition and Health AND The Institute of Biological and Environmental Sciences, University of Aberdeen, Bucksburn, Aberdeen, Scotland, United Kingdom AND Department of Clinical Nutrition, School of Nutritional sciences and Dietetic, Tehran University of Medical Sciences, Tehran, Iran John R-Speakman Division of Obesity and Metabolic Health, Rowett Institute of Nutrition and Health AND The Institute of Biological and Environmental Sciences, University of Aberdeen, Bucksburn, Aberdeen, Scotland, United Kingdom Joanne Stewart Division of Obesity and Metabolic Health, Rowett Institute of Nutrition and Health AND The Institute of Biological and Environmental Sciences, University of Aberdeen, Bucksburn, Aberdeen, Scotland, United Kingdom Diane M-Jackson Division of Obesity and Metabolic Health, Rowett Institute of Nutrition and Health AND The Institute of Biological and Environmental Sciences, University of Aberdeen, Bucksburn, Aberdeen, Scotland, United Kingdom 2015 10 05 2015 10 05 Background: Previous studies have suggested that sex may be a factor influencing basal metabolic rate (BMR) in adults and school age children. However, few data are available about the effects of sex on BMR in pre-school children. In the present study, we investigated whether sex differences contribute to variations in BMR in pre-school age children. Methods: Measurements were made on thirty children aged 2-6 years (14 male and 16 female). Measurements were taken of height, age, weight, and total body composition, which  was  determined  using  both  dual-energy X-ray  absorptiometry (DXA)  and deuterium dilution.  The  DXA  was  also  used  to  determine  body composition  in different regions of the body. BMR was measured by indirect calorimetry. Results: We  found  no  significant sex  differences with  respect  to  age  (F  =  0, p = 0.998), weight (F = 0.02, p = 0.884), height (F = 0.33, p = 0.570), and body mass index standard deviation score (F = 0.51, p = 0.480). In addition, no significant difference was found between boys and girls for total fat free mass (FFM) (F = 1.30, p = 0.265) and fat mass (FM) (F = 3.16, p = 0.090) measured by DXA, and total FFM (F = 0.79, p = 0.380) and FM (F = 3.38, p = 0.080) obtained by deuterium dilution. There was no significant difference between pre-school boys and girls for BMR (F = 0.16, p = 0.690). In a multiple regression analysis, only log weight was significantly associated to BMR. The explain variation was 75.3%. Conclusion: In conclusions we found no significant differences in body composition between pre-school boys and girls and no sex effect on BMR in this age group. https://jnsd.tums.ac.ir/index.php/jnsd/article/view/13 https://jnsd.tums.ac.ir/index.php/jnsd/article/download/13/13