Fat and fat-free mass of healthy Swedish children show tracking during early life, but there are differences.

AIM: Obesity may start early in life. We investigated relationships between size and body composition variables in infancy and at 4 years of age using valid estimates of body composition. The results were compared to those obtained when body mass index (BMI) was used to estimate body fatness at 4 years. METHODS: Using air displacement plethysmography, size, fat mass and fat-free mass were studied, between 2007 and 2015, in 253 full-term healthy Swedish children at 1 week, 12 weeks and 4 years of age. RESULTS: Positive associations between variables in infancy and at 4 years were found at 1 and 12 weeks for weight, height, BMI, fat-free mass and fat-free mass index (p ≤ 0.002) and for fat mass, per cent body fat and fat mass index (p ≤ 0.04) at 12 weeks. Fat mass gained during infancy correlated positively (p ≤ 0.031) with per cent fat mass, fat mass index and BMI, all at 4 years. In girls, gains in fat-free mass during infancy correlated with BMI (p = 0.0005) at 4 years. CONCLUSION: The results provide information regarding body composition trajectories during early life and demonstrate limitations of BMI as a proxy for body fatness when relating early weight gain to variables, relevant for later obesity risk.

Longitudinal study of the maternal insulin-like growth factor system before, during and after pregnancy in relation to fetal and infant weight.

BACKGROUND: The maternal insulin-like growth factor (IGF) system is considered to be involved in fetal growth regulation. However, available data linking this system to fetal growth are contradictory and incomplete. AIMS: To measure components of the IGF system before, during and after pregnancy in healthy women and to relate these results, and their changes during pregnancy, to fetal weight (gestational week 31) and birth weight. METHODS: Serum concentrations of IGF-I, IGF-II, IGF-binding protein (IGFBP)-1, IGFBP-3 and IGFBP-3 protease activity were assessed in 23 women before conception, at weeks 8, 14, 20, 32 and 35 of pregnancy and 2 weeks postpartum. The data were analyzed using simple and multiple linear regression. RESULTS: One third of the variability in fetal weight was explained by IGF-I in combination with IGFBP-3 protease activity, both assessed at gestational week 32 (p = 0.013). Birth weight was negatively correlated (r = -0.43 to -0.59) with IGFBP-1 at gestational week 20 (p = 0.041), 32 (p = 0.012) and 35 (p = 0.003). CONCLUSION: We propose there is a finely tuned balance among the components of the IGF system, providing a means for fetal growth regulation.

Longitudinal assessment of body composition in healthy Swedish children from 1 week until 4 years of age.

BACKGROUND/OBJECTIVES: Knowledge of longitudinal body composition development is required to identify the mechanisms behind childhood overweight and obesity and to prevent these conditions. However, accurate data on this development in early childhood are lacking. Our aim was to describe the longitudinal body composition development in healthy young Swedish children. SUBJECTS/METHODS: Body size and composition were assessed in 26 children using air-displacement plethysmography (1 and 12 weeks and 4.4 years of age) and isotope dilution (1.5 and 3 years of age) and compared with available reference data. RESULTS: Body fat (%) for boys (n=16) was 12.8±3.9 (1 week), 25.6±4.8 (12 weeks), 28.2±3.8 (1.5 years), 27.3±5.1 (3 years) and 26.1±3.5 (4.4 years). For girls (n=10) these values were 15.3±2.9, 25.7±3.9, 27.9±3.3, 26.3±7.2 and 26.0±5.3, respectively. These values were above the Fomon reference values at 1.5 years of age and later and higher than the Butte reference (P<0.05) for boys at 1.5 years of age. At all ages the coefficients of variation were higher for body fat (%) (12-30%) than for BMI (4-11%). CONCLUSIONS: At 4 years of age our children had more body fat than indicated by reference data. This high level may have already been established at 1.5 years of age but our small sample and the lack of appropriate reference data limit the possibility of drawing firm conclusions. Our results demonstrate the limitations of BMI when investigating overweight and obesity in early life and highlight the need for appropriate reference body composition data in infants and young children.European Journal of Clinical Nutrition advance online publication, 23 August 2017; doi:10.1038/ejcn.2017.125.

Evaluation of the wrist-worn ActiGraph wGT3x-BT for estimating activity energy expenditure in preschool children.

BACKGROUND/OBJECTIVES: Easy-to-use and accurate methods to assess free-living activity energy expenditure (AEE) in preschool children are required. The aims of this study in healthy preschool children were to (a) evaluate the ability of the wrist-worn ActiGraph wGT3x-BT to predict free-living AEE and (b) assess wear compliance using a 7-day, 24-h protocol. SUBJECTS/METHODS: Participants were 40 Swedish children (5.5±0.2 years) in the Mobile-based intervention intended to stop obesity in preschoolers (MINISTOP) obesity prevention trial. Total energy expenditure (TEE) was assessed using the doubly labeled water method during 14 days. AEE was calculated as (TEEx0.9) minus predicted basal metabolic rate. The ActiGraph accelerometer was worn on the wrist for 7 days and outputs used were mean of the daily and awake filtered vector magnitude (mean VM total and mean VM waking). RESULTS: The ActiGraph was worn for 7 (n=34, 85%), 6 (n=4, 10%), 5 (n=1, 2.5%) and 4 (n=1, 2.5%) days (a valid day was ⩾600 awake minutes). Alone, mean VM total and mean VM waking were able to explain 14% (P=0.009) and 24% (P=0.001) of the variation in AEE, respectively. By incorporating fat and fat-free mass in the models 58% (mean VM total) and 62% (mean VM waking) in the variation of AEE was explained (P<0.001). CONCLUSIONS: The wrist-worn ActiGraph wGT3x-BT in combination with body composition variables explained up to the 62% of the variation in AEE. Given the high wear compliance, the wrist-worn ActiGraph has the potential to provide useful information in studies where physical activity in preschool children is measured.

Strengthening the Reporting of Observational Studies in Epidemiology - nutritional epidemiology (STROBE-nut): An extension of the STROBE statement.

Concerns have been raised about the quality of reporting in nutritional epidemiology. Research reporting guidelines such as the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) statement can improve quality of reporting in observational studies. Herein, we propose recommendations for reporting nutritional epidemiology and dietary assessment research by extending the STROBE statement into Strengthening the Reporting of Observational Studies in Epidemiology - Nutritional Epidemiology (STROBE-nut). Recommendations for the reporting of nutritional epidemiology and dietary assessment research were developed following a systematic and consultative process, co-ordinated by a multidisciplinary group of 21 experts. Consensus on reporting guidelines was reached through a three-round Delphi consultation process with 53 external experts. In total, 24 recommendations for nutritional epidemiology were added to the STROBE checklist. When used appropriately, reporting guidelines for nutritional epidemiology can contribute to improve reporting of observational studies with a focus on diet and health.

Gestational weight gain according to Institute of Medicine recommendations in relation to infant size and body composition.

BACKGROUND: Intrauterine life may be a critical period for programming childhood obesity; however, there is insufficient knowledge concerning how gestational weight gain (GWG) affects infant fat mass (FM) and fat-free mass (FFM). OBJECTIVES: The aim of this study was to investigate relationships between GWG according to Institute of Medicine (IOM) recommendations and infant size, FM and FFM. We also investigated if the associations were different for normal-weight and overweight/obese women. METHODS: This study included 312 healthy Swedish mother-infant pairs. Infant body composition at 1 week of age was assessed using air-displacement plethysmography. Maternal GWG was defined as below, within or above the 2009 IOM recommendations. Multiple regression analyses were used. RESULTS: Compared with women whose weight gain was within IOM recommendations, women with weight gain below the recommendations had infants that were shorter (-0.7 cm, P = 0.008) when adjusting for confounders. Normal-weight women exceeding IOM recommendations had infants with higher FM (+58 g, P = 0.008) compared with normal-weight women who gained within the recommendations. No corresponding association was observed for overweight/obese women. CONCLUSIONS: Inadequate GWG was associated with shorter infants, while excessive GWG was associated with greater infant FM for women who were of normal weight before pregnancy.

Changes in adipose tissue volume and distribution during reproduction in Swedish women as assessed by magnetic resonance imaging.

Adipose tissue volume (ATV; total, subcutaneous, and nonsubcutaneous) was assessed by magnetic resonance imaging in the whole body and in six body compartments of 15 healthy Swedish women before pregnancy and 5-10 d, and 2, 6, and 12 mo postpartum. ATV increased by 5.43 +/- 4.72 L (mean +/- SD) during pregnancy and decreased by 3.18 +/- 4.61 L during the first 6 mo postpartum. The women had more ATV (2.86 +/- 2.32 L) 12 mo after delivery than before pregnancy. Of the ATV gained during pregnancy, 76% was placed subcutaneously and the decrease postpartum was due to a loss of subcutaneous ATV. During pregnancy, 68% of the increased ATV was placed in the trunk and 16% in the thighs. Postpartum fat was mobilized more completely from the thighs than from the trunk. For all variables studied variations between women were large. The results also show that women with a high weight gain during pregnancy retain lean tissue in their bodies.

Effect of protein intake on protein and nitrogen composition of breast milk.

The effect of a low and a high protein diet (approximately 8 and 20% energy from protein, respectively) on the contents of different nitrogen-containing substances in breast milk was studied on three healthy Swedish mothers in full lactation. Each experimental diet was fed during a 4-day period and milk samples were collected during the last day. The milk volume was estimated by weighing the child before and after each feeding. The 24-hr outputs as well as concentrations of total nitrogen, true protein, and nonprotein nitrogen were significantly higher when the subjects consumed the high protein rather than the low protein diet. The higher content of nonprotein nitrogen was due to increased urea levels as well as to increased levels of free amino acids. Milk urea levels were closely correlated with plasma urea levels in samples obtained after overnight fasting when the subjects had consumed the experimental diets for 4 days. The 24-hr output of lactoferrin, alpha-lactalbumin, and serum albumin were higher when the subject consumed the high protein diet as compared to the low protein diet but the differences were not significant.

Changes in total body fat during the human reproductive cycle as assessed by magnetic resonance imaging, body water dilution, and skinfold thickness: a comparison of methods.

Total body fat and fat-free mass were assessed by magnetic resonance imaging (TBFMRI and FFMMRI) in 11-16 healthy Swedish women before pregnancy and 5-10 d and 2, 6, and 12 mo after delivery. On these occasions, TBF was also measured by the body water dilution (TBFBWD) and skinfold-thickness (TBFSFT) techniques. The results were used to compare changes in TBFSFT and TBFBWD during reproduction with changes in TBFMRI. TBFBWD was 1.5-4.0 kg higher than TBFMRI and at all postpartum measurements the difference between these estimates increased significantly with increased body fat content. This difference was also significantly higher 6 mo after delivery than it was 2 and 12 mo postpartum. The possibility that this was due to variations in the degree of hydration of FFM postpartum was considered. TBFSFT was 1.7-3.1 kg higher than TBFMRI and this difference increased with increasing body fat content. The agreement between changes in TBFMRI and TBFSFT was different during different times in the reproductive cycle and was also influenced by the amount of fat lost or gained. The findings thus suggest that there is a risk for bias when changes in TBF during reproduction are estimated by the skinfold-thickness technique as well as by isotope dilution.

Casein content of human milk.

Three methods for estimating the casein content of human milk were tested; isoelectric precipitation with washing and correction for co-precipitating proteins, sedimentation by ultracentrifugation, and indirect analysis (ie analyzing for the content of the major whey proteins and subtracting these from the total protein content). Gel electrophoresis and amino acid analysis were used to confirm some of the results. The casein content (mg/ml) of mature human milk (n = 9) was 2.33 +/- 1.69 by isoelectric precipitation, 1.80 +/- 0.48 by sedimentation and 2.96 +/- 1.08 by the indirect approach. A probable partition of nitrogen in breast milk would be casein N: whey protein N: non-protein N of 20:50:30; ie the correct ratio of casein nitrogen: whey nitrogen is approximately 20:80. Analysis of trace elements and minerals demonstrates that of total Ca 10%, Mg 5%, Zn 28%, Cu 17%, and Fe 27% is bound to casein when prepared by ultracentrifugation while isoelectric precipitation causes a redistribution of some of these elements. Since the protein ratio of human milk is considered a guideline when manufacturing infant formulas, these findings should be considered with regard to infant nutrition.

Effect of reduced energy intake versus increased physical activity on the outcome of nitrogen balance experiments in man.

The effects of energy deficiency created by a reduced energy intake versus an increased physical activity on urinary nitrogen excretion, nitrogen balance and the biological value of the dietary protein (0.57 g/kg/day from a mixed diet) are reported. Two experiments, 21 and 27 days respectively, designed to even out possible effects of time on nitrogen balance, were conducted on 12 young adult men and women. During energy deficiency, urinary nitrogen increased while nitrogen balance and biological value decreased. No significant differences between the two kinds of energy deficiency were found but the effect on the parameters studied tended to be less pronounced the longer the subjects had been on the experimental diets.

Resting metabolic rate and body composition of healthy Swedish women during pregnancy.

Body weight, resting metabolic rate (RMR), total body potassium (TBK), and total body water were measured and total body fat (TBF) was calculated in a longitudinal study of 22 pregnant, healthy Swedish women. Measurements were made before pregnancy, at gestational weeks 16-18, 30, and 36, and 5-10 d and 6 mo postpartum. RMR increased more during pregnancy than previous estimates on well-nourished women showed and the increase was significantly correlated with the birth weight of the baby. TBK decreased during the first part of pregnancy; measurements at weeks 16-18 and 30 were significantly lower than the prepregnancy value and changes in TBK and RMR were significantly correlated. TBF gain during pregnancy was 5.8 +/- 4.0 kg and 60% was already gained by gestational weeks 16-18. Gain in fat was not correlated with birth weight.

Calculation and determination of metabolizable energy in mixed diets to humans.

Several approaches are currently in use for calculating metabolizable energy of mixed diets from the foods and nutrients they contain. This study compares the metabolizable energy content of six low fiber and one high fiber diet as calculated by conventional procedures (ie, using Atwater's general factors, Merrill and Watts specific factors, and the British procedure where the monosaccharide equivalent of available carbohydrates is multiplied by 3.75 kcal/g) with values for metabolizable energy measured in balance experiments on human subjects. For the low fiber diets, the conventional procedures for calculation of metabolizable energy showed an average deviation between calculated and measured values of up to about 6% of the value obtained in balance experiments. For the high fiber diet Merrill and Watts specific factors and Atwater's general factors were superior to the British approach for calculation of metabolizable energy. Fecal energy content in relation to intake of undigestible energy is discussed.

A longitudinal study of the protein, nitrogen, and lactose contents of human milk from Swedish well-nourished mothers.

The contents of total nitrogen, nonprotein nitrogen, lactose, and individual milk proteins have been determined in human milk from well-nourished Swedish mothers. Breast milk samples from 50 mothers at different stages of lactation (up to 170 days) were collected. Furthermore, three mothers gave samples repeatedly throughout the whole lactation period. The protein content in mature milk was found to be 0.8 to 0.9% by amino acid analysis. The nitrogen content and the contents of the major human milk whey proteins, alpha-lactalbumin and lactoferrin, are very high for the first few days, then decrease rapidly and reach, thereafter, the more slowly declining level of mature milk. Nonprotein nitrogen and the nonspecific milk protein serum albumin are present in constant concentrations throughout lactation. The daily milk volumes were determined and found to be 500 to 600 ml in the very early part and 700 to 800 ml in the later part of the lactation period.

Protein evaluation of mixed diets in young adults, growing pigs, and growing rats.

The protein quality of mixed diets was tested using the nitrogen balance technique with a slope-ratio approach in adults, growing pigs, and rats. For diet A (milk, cereals, potatoes, meat, fish, and vegetables) and diet B (milk, cereals, and potatoes) the slope of the regression line, nitrogen balance = f (nitrogen intake) was calculated and expressed in percentage of the slope obtained for diets containing egg white protein. In man, diet A was significantly better than the egg white protein diet which was similar to diet B. In pigs, diets A and B were significantly better than egg white protein. In rats, egg white protein was significantly better than diets A and B. The results are of interest in relation to the recommendations by FAO/WHO regarding adjustment of protein allowance in relation to dietary protein quality.

Effect of oral contraceptives on composition and volume of breast milk.

Nitrogen and protein composition was determined in milk from women using oral contraceptives during lactation. Total nitrogen and nonprotein nitrogen as well as lactose and the individual milk proteins lactoferrin, alpha-lactalbumin, and serum albumin were analyzed before introduction of oral contraceptives and thereafter throughout the lactation period. Twenty-four hour milk volumes were registered by weighing the infant before and after each feeding. The four oral contraceptives used consisted of different combinations of d-norgestrel, megestrolacetate, and ethinylestradiol. Significant changes were observed between groups and controls for all parameters studied. However, the changes observed were generally within the physiological variation of normal breast milk. It is suggested that the use of oral contraceptives during lactation should be limited.

PIP: The present article reports the results of an investigation on the effects of OC (oral contraception) on lactation performance and on composition of breast milk. Mothers collaborating to the study were on combined OCs or on progestin only OCs. Before and after introduction of OC, nitrogen lactose, lactogerrin, alpha-lactabbumin, and serum albumin were analyzed; milk volume was measured by weighing the infant before and after each feeding. Significant changes were found in concentration of total protein and in individual milk protein, the magnitude of changes varying between components investigated; changes in daily milk volume were also observed. The magnitude of changes were reputed to be still within the normal range, and not to be of nutritional importance. However, negative effects could be observed in marginally or severely malnourished mothers. Use of OC during lactation should be carefully considered, and, if chosen, the lowest possible dose should be given.

Estimation of body fat in healthy Swedish women during pregnancy and lactation.

Reliable estimates of changes in body fat are important in studies of energy requirements during human reproduction. It is not known if current methods for the estimation of total body fat (TBF) are adequate for this purpose. In this paper earlier reported data from 29 women are used to show how methodology affects estimates of changes in TBF during reproduction. Skinfold thicknesses are also reported and equations relating these measurements to TBF were developed and used to demonstrate how well the skinfold technique could estimate such changes. No correlation was found between changes in body weight and body fat during early pregnancy or between the maternal changes in body weight and body fat over the complete pregnancy. These findings are tentatively explained by changes in the degree of hydration of the body.

Adipose tissue distribution as assessed by magnetic resonance imaging and total body fat by magnetic resonance imaging, underwater weighing, and body-water dilution in healthy women.

A method for estimating total body fat (TBF) and the amount and distribution of adipose tissue in humans by using magnetic resonance imaging (MRI) is described. Thirty transaxial images of subjects were taken by a nuclear magnetic imager (0.02 T). Adipose tissue volume was calculated from adipose tissue area in each image and from the distances between images. The CV when estimating total volume of body adipose tissue was 1.5%. TBF of healthy Swedish women was estimated by the MRI method (n = 25), by underwater weighing (UWW) (n = 20), and by body-water dilution (BWD) (n = 23). When assessed by MRI and BWD, women contained 1.4 +/- 2.9% less and 4.7 +/- 4.0% more TBF, respectively, than when assessed by UWW. On average, 74.2% of total adipose tissue volume was situated subcutaneously. Subcutaneous fat:fat-free body weight and nonsubcutaneous fat:fat-free body weight were both significantly correlated with percent TBF but the women stored excess fat subcutaneously rather than nonsubcutaneously.

Energy metabolism, body composition, and milk production in healthy Swedish women during lactation.

Variables of relevance to energy requirements during reproduction were studied in 23 healthy lactating Swedish women. Body composition and resting metabolic rate (RMR) were studied before pregnancy and three times postpartum. Energy intake was studied before pregnancy and, together with breast-milk production, 2 mo postpartum. The women gained 5.8 +/- 4.2 kg fat during pregnancy and their average fat content was unchanged during the first 2 mo of lactation whereas a slight loss (1.7 +/- 4.2 kg) occurred during the following 4 mo. RMR increased slightly during lactation in spite of a decrease in fat-free body weight 2 and 6 mo postpartum. Energy intake increased during lactation (280 +/- 440 kcal/d). The women produced 740 +/- 150 g breast milk/d containing 0.64 +/- 0.08 kcal/g. The results indicate that current estimates of energy needs during lactation may be too high.

Total energy expenditure of healthy Swedish women during pregnancy and lactation.

Total energy expenditure (TEE) was estimated in healthy Swedish women by the doubly labeled water method in a longitudinal study during pregnancy and lactation. Measurements were made before pregnancy (A); in gestational weeks 16-18 (B), 30 (C), and 36 (D); as well as 2 (F) and 6 (G) mo after delivery. When the results were interpreted, earlier published data regarding resting metabolic rate (RMR), energy intake, and energy in breast milk were also considered. TEE (MJ/d) and TEE/RMR were 10.5 +/- 2.2 (mean +/- SD) and 1.87 +/- 0.42 (n = 28), 9.6 +/- 2.8 and 1.65 +/- 0.67 (n = 22), 12.5 +/- 3.4 and 1.82 +/- 0.45 (n = 22), 12.2 +/- 4.1 and 1.66 +/- 0.52 (n = 19), 10.6 +/- 2.0 and 1.82 +/- 0.41 (n = 23), and 10.8 +/- 2.7 and 1.79 +/- 0.42 (n = 23) at A, B, C, D, F, and G, respectively. The results indicated that physical activity tended to be decreased during early pregnancy. Taking changes in body energy stores into consideration, it was estimated that subjects recorded 86% and 77% of their energy intakes at A and F respectively.