Introduction The age of menarche is the age of ovarian maturation and is defined by the final stages of female growth. It is a genetically determined physiological trait that significantly modifies somatic and body composition characteristics and is highly sensitive to socio-environmental conditions. Objectives To determine the association between age at menarche, amount and distribution of body fat and nutritional status in a sample of girls from Madrid of the same chronological age. Material and methods We analysed 126 12-year-old girls classified according to the age at menarche. Height, weight, umbilical circumference and five subcutaneous skinfolds were measured according to the standards of the International Biological Programme, and body mass index, waist-to-height ratio, sum of subcutaneous skinfolds and fat percentage were estimated. Comparisons of means for the different variables were made using Student's t-test or U-Man-Whitney test. Results There were notable differences observed between girls with and without menarche. The former exhibited a higher body mass index (20.4 ± 3.7 vs. 18.1 ± 3.1), fold sum (60 ± 18 vs. 50 ± 17) and fat percentage (26.6 ± 3.6 vs. 24.0 ± 3.7) compared to the latter. Nutritional status was found to be associated with this maturational characteristic, with excess weight (overweight + obesity) affecting 9.6% of premenarchal girls compared to 22.2% of postmenarchal girls. Conclusions The present study shows a positive association between age at menarche, the amount and distribution of body fat and female nutritional status. For the same chronological age, post-menarchal girls had higher averages for all anthropometric variables of body size and composition, except for waist to height ratio. Also, the presence of menarche doubles the prevalence of excess weight.