This study aimed to assess the validity of mid-arm circumference (MAC), also known as mid-upper arm circumference (MUAC), for classification of high body fatness in Namibian adolescent girls and women and to test whether classification accuracy of MUAC was higher than the traditional simple proxy for high fatness, the BMI. In 206 adolescent girls aged 13–19 years and 207 adult women aged 20–40 years, we defined obesity conventionally (BMI-for-age Z score ≥ 2·00, adolescents; adults BMI ≥ 30·0 kg/m2) and also defined obesity using published MAC cut-off values. 2H oxide dilution was used to measure total body water (TBW) to define high body fat percentage (≥ 30 % in the adolescents, ≥ 38 % in the adults), and we compared the ability of BMI and MAC to classify high body fatness correctly using sensitivity, specificity and predictive values. In the adolescents, obesity prevalence was 9·2 % (19/206) using BMI-for-age and 63·2 % (131/206) using TBW; sensitivity of BMI-for-age was 14·5 % (95 % CI 9·1, 22·0 %) but was improved significantly using MAC of 22·6 cm (sensitivity 96·9 %; 95 % CI 92·1 %, 99·3 %). In the adults, obesity prevalence was 30·4 % (63/207) using BMI and 57·0 % (118/207) using TBW, and sensitivity of BMI was 52·5 % (95 % CI 43·6, 62·2 %), but using a MAC of 30·6 cm sensitivity was 72·8 % (95 % CI 66·4, 82·6 %). Surveillance of obesity in African adolescent girls and adult women is likely to be improved substantially by use of MAC as an alternative to the BMI-for-age and BMI.

Iodine intake and excretion vary widely; however, these variations remain a large source of geometric uncertainty. The present study aims to analyse variations in iodine intake and excretion and provide implications for sampling in studies of individuals or populations. Twenty-four healthy women volunteers were recruited for a 12-d sampling period during the 4-week experiment. The duplicate-portion technique was used to measure iodine intake, while 24-h urine was collected to estimate iodine excretion. The mean intra-individual variations in iodine intake, 24-h UIE (24-h urinary iodine excretion) and 24-h UIC (24-h urinary iodine concentration) were 63, 48 and 55 %, respectively, while the inter-individual variations for these parameters were 14, 24 and 32 %, respectively. For 95 % confidence, approximately 500 diet samples or 24-h urine samples should be taken from an individual to estimate their iodine intake or iodine status at a precision range of ±5%. Obtaining a precision range of ±5% in a population would require twenty-five diet samples or 150 24-h urine samples. The intra-individual variations in iodine intake and excretion were higher than the inter-individual variations, which indicates the need for more samples in a study on individual participants.

During pregnancy, adult women with a normal BMI synthesise extra amino acids after an overnight fast by increasing body protein breakdown and decreasing amino acid oxidation. It is not known whether adolescent girls can make these adaptations during pregnancy. The present study aimed to measure and compare the protein, glutamine and alanine kinetics of adult women and adolescent girls at early-, mid- and late-pregnancy. Kinetics were measured in the overnight fasted state using intravenous infusions of 13C-leucine, 15N-glutamine and 15N-alanine in ten adults and twenty adolescents aged 14–17 years in the first and second trimesters (phase 1 study) and infusions of 13C-leucine and 15N2-urea in ten adults and eleven adolescents aged 16–17 years in the first and third trimesters (phase 2 study). In phase 1 study, there were no significant differences between the groups with regard to any of the kinetic parameters measured. In both groups, leucine flux increased (P< 0·05), the percentage of leucine flux oxidised decreased (P< 0·05) and non-oxidative leucine disposal to protein synthesis increased (P< 0·05) from the first to the second trimester. In phase2 study, leucine flux was significantly slower (P< 0·05) in the adult group than in the adolescent group during both trimesters, and whole-body leucine flux and non-oxidative leucine disposal increased significantly in the adolescent group (P< 0·05, respectively) and were higher in the adult group from the first to the third trimester. These results suggest that similar to their adult counterparts after an overnight fast, adolescent girls with a normal BMI provide extra amino acids required for net protein deposition during pregnancy by increasing protein breakdown and decreasing amino acid oxidation.