Body mass index growth trajectories associated with the different parameters of the metabolic syndrome at adulthood.

BACKGROUND: Growth trajectories have shown to be related to obesity and metabolic risks in later life, however body mass index (BMI) trajectories according to the presence or absence of metabolic syndrome (MS) and its parameters in adulthood are scarce in literature. OBJECTIVES: To investigate BMI trajectories during childhood in relation to MS and its parameters in adult age. METHODS: A total of 1919 subjects (43.4% male, 20-60 y) participated in this retrospective cohort study. Height, weight, waist circumference (WC), blood glucose, high-density lipoprotein cholesterol, triglycerides and blood pressure were measured at adulthood. Childhood weight and height were collected retrospectively from health booklets. Differences between BMI growth curves of subjects with and without MS were assessed using mixed models for correlated data. RESULTS: BMI trajectories differed according to the presence or not of MS at adulthood, from the age of 4 years forward (all P<0.05), to the presence or not of hypertriglyceridemia from 1.5 years forward (all P<0.05), and to WC>94 cm (men) / 80 cm (women) compared to lower WC, at all ages (all P<0.05). CONCLUSIONS: BMI growth curves differ according to the presence or not of MS at adulthood, but differences only appeared after the age of 4 years. Changes vary according to the MS parameters considered. Deviation of the MS-associated BMI curve from normal pattern could correspond to alteration in body composition. These differences in BMI trajectories during childhood support the theory of an early origin of the MS, justifying early prevention.

Age at adiposity rebound: determinants and association with nutritional status and the metabolic syndrome at adulthood.

OBJECTIVE: Early-life growth characteristics and in particular age at adiposity rebound (AR), have been shown to impact nutritional status later in life but studies investigating the association with long-term health remain scarce. Our aims were to identify determinants of age at AR and its relationship with nutritional status and cardiometabolic risk factors at adulthood. DESIGN: A total of 1465 subjects aged 20-60 years participated in this retrospective cohort study. Height, weight, waist circumference, blood glucose, lipids and blood pressure were measured at adulthood. Childhood weight, height, gestational age, birth weight and early nutrition were collected retrospectively from health booklets and age at AR was assessed. Participants self-reported parental silhouettes. Associations were assessed using multiple linear and logistic regression. RESULTS: An earlier AR was associated with higher body mass index and waist circumference at adulthood in both men and women (P<0.0001). In addition, women with an earlier occurrence of AR had higher triglyceride (P=0.001), low-density lipoprotein-cholesterol (P=0.001), systolic (P=0.02) and diastolic blood pressure (P=0.04) at adulthood. Both men (odds ratio (OR) (95% confidence interval (CI)): 0.82 (0.70-0.95)) and women (OR (95% CI): 0.84 (0.73-0.96) with an AR occurring earlier were more likely to develop a metabolic syndrome. Larger parental silhouette was associated with an earlier AR. CONCLUSIONS: This long-term study showed that age at AR was associated with nutritional status and metabolic syndrome at adulthood. These results highlight the importance of monitoring childhood growth so as to help identify children at risk of developing an adverse cardiometabolic profile in adulthood. AR determinants for use in overweight surveillance were identified.

Association of nutrition in early life with body fat and serum leptin at adult age.

BACKGROUND: There is overwhelming evidence that experiences during early life could have long-term health consequences. However, the role of early nutrition in programming obesity and leptin resistance is still poorly understood. OBJECTIVE: We aimed at determining whether nutritional intakes in early life are associated with body composition and hormonal status at 20 years. SUBJECTS: Healthy infants participating in the two-decade-long prospective ELANCE (Etude Longitudinale Alimentation Nutrition Croissance des Enfants) study were examined at 10 months and 2 years. At 20 years, weight, height, subscapular and triceps skinfold thicknesses, fat mass (FM) and fat-free mass (FFM) assessed via bioelectrical impedance analysis, and serum leptin concentration were recorded in 73 subjects still participating in the follow-up. RESULTS: In adjusted linear regression models, an increase by 100 kcal in energy intake at 2 years was associated with higher subscapular skinfold thickness (ß=6.4% SF, 95% confidence interval 2.53-10.30, P=0.002) and higher FFM (0.50 kg, 0.06-0.95, P=0.03) at 20 years. An increase by 1% energy from fat at 2 years was associated with lower subscapular skinfold thickness (-2.3% SF, -4.41 to -0.18, P=0.03), lower FM (-0.31 kg, -0.60 to -0.01, P=0.04) and lower serum leptin concentration (-0.21 µg l(-1), -0.39 to -0.03, P=0.02) at 20 years. CONCLUSIONS: Low-fat intake in early life was negatively associated with body fat (particularly at the trunk site) and serum leptin concentration at 20 years, suggesting that early low-fat intake could increase the susceptibility to develop overweight and leptin resistance at later ages. These findings substantiate current recommendations against restricting fat intake in early life and open new directions for investigating the origin of obesity.

Correlates of sedentary behavior in 7 to 9-year-old French children are dependent on maternal weight status.

OBJECTIVE: Sedentary behavior accounts for overweight and obesity, independently of physical activity. Correlates of sedentary behavior have not been extensively reported in the literature. Our objective was to determine factors associated with such behavior in 7 to 9-year-old French children in 2007, and to assess interactions between the identified correlates. DESIGN: A nationally representative sample of 2525 children participated in the study. Television viewing, video/computer duration and characteristics of the children and their parents were assessed using a questionnaire completed by the parents. Correlates of television viewing (<2 h per day versus ≥ 2 h per day) as a proxy for sedentary behavior were estimated using multivariate logistic regression. RESULTS: On an average, children spent more than 2 h per day in front of a screen (television: 1 h 32 min (s.e.m.: ± 0 h 02 min); video/computer: 0 h 40 min (± 0 h 02 min)). Television viewing duration was associated with sociodemographic (child's age, weight status, socio-economic characteristics of the family) and behavioral factors (physical and lifestyle activities). In children of non-overweight mothers, risk of spending ≥ 2 h per day in front of a television was significantly higher in those over 9 (versus 7 years: odds ratio (OR): 2.07; 95% confidence intervals (CI): 1.04-4.11), living in an educational priority zone (OR: 1.62; 95% CI: 1.08-2.44), who were not members of a sports team (OR: 2.24; 95% CI: 1.47-3.41), nor declared active by parents (OR: 1.92; 95% CI: 1.13-3.25), and whose parents' education level was lower than high school (OR: 1.84; 95% CI: 1.24-2.72). In contrast, in children of overweight mothers, only the criteria of ≥ 4 children in the family (versus 2-3 children: OR: 1.87; 95% CI: 1.05-3.35) and no reported parental occupation (versus manager or white collar: OR: 0.29; 95% CI: 0.11-0.76) were associated with watching television ≥ 2 h per day. CONCLUSIONS: Correlates of sedentary behavior in 7 to 9-year-old children vary according to maternal overweight. Maternal body mass index must therefore be taken into account when developing strategies to prevent a sedentary lifestyle in children.

Prevalence of overweight in 6- to 15-year-old children in central/western France from 1996 to 2006: trends toward stabilization.

OBJECTIVE: The prevalence of overweight in children has markedly increased over the past few decades in France, as in all Western countries. We sought to describe the yearly prevalence of childhood overweight from 1996 to 2006 and to assess whether a shift in trends could be observed dating from the time the Nutrition and Health National Program (PNNS) was set up in France in 2001, in particular according to gender, age and family economic status. DESIGN: We used annual overweight prevalence of standardized 6- to 15-year-old populations (total=26 600) with weight and height measured at health examination centers in the central/western part of France between 1996 and 2006. Regression slopes of overweight prevalence were evaluated between 1996 and 2006, and specifically between 1996 and 2001, and 2001 and 2006. The annual prevalence and estimated slopes were compared in subgroups, taking into account gender, age and economic status of the family. RESULTS: The prevalence increased between 1996 (11.5%) and 1998 (14.8%) and was stable between 1998 and 2006 (15.2%). According to linear regression, the overall trend in prevalence of overweight children between 1996 and 2006 was stable (slope=0.19, P=0.08). Similarly, the prevalence of overweight increased between 1996 and 1998 in boys and girls, in 6-10 year olds, in 11-15 year olds and in non-disadvantaged children, and remained stable thereafter. The prevalence of overweight in the disadvantaged group increased between 1996 (12.8%) and 2001 (18.9%) (slope=1.16, P=0.004) and was stable between 2001 and 2006 (18.2%) (slope=0.09, P=0.78). CONCLUSION: The results of this study reveal a stable prevalence of overweight since 1998 in most groups studied, and since 2001 in the disadvantaged group.

[WHO growth standards for infants and young children]. / Les standards de croissance de l'Organisation mondiale de la santé pour les nourrissons et les jeunes enfants.

The growth pattern of healthy breastfed infants deviates to a significant extent from the NCHS/WHO international reference. In particular, this reference is inadequate because it is based on predominantly formula-fed infants, as are most national growth charts in use today. The WHO multicentre growth reference study (MGRS), aimed at describing the growth of healthy breastfed infants living in good hygiene conditions, was conducted between 1997 and 2003 in 6 countries from diverse geographical regions: Brazil, Ghana, India, Norway, Oman and the United States. The study combined a longitudinal follow-up of 882 infants from birth to 24 months with a cross-sectional component of 6669 children aged 18-71 months. In the longitudinal follow-up study, mothers and newborns were enrolled at birth and visited at home a total of 21 times at weeks 1, 2, 4 and 6; monthly from 2-12 months; and bimonthly in the 2nd year. The study populations lived in socioeconomic conditions favorable to growth. The individual inclusion criteria for the longitudinal component were: no known health or environmental constraints to growth, mothers willing to follow MGRS feeding recommendations (i.e., exclusive or predominant breastfeeding for at least 4 months, introduction of complementary foods by 6 months of age and continued breastfeeding to at least 12 months of age), no maternal smoking before and after delivery, single-term birth and absence of significant morbidity. Term low-birth-weight infants were not excluded. The eligibility criteria for the cross-sectional component were the same as those for the longitudinal component with the exception of infant feeding practices. A minimum of 3 months of any breastfeeding was required for participants in the study's cross-sectional component. Weight-for-age, length/height-for-age, weight-for-length/height and body mass index-for-age percentile and Z-score values were generated for boys and girls aged 0-60 months. The full set of tables and charts is presented on the WHO website (www.who.int/childgrowth/en), together with tools such as software and training materials that facilitate their application. The WHO child growth standards were derived from children who were raised in environments that minimized constraints to growth, such as poor diets and infection. In addition, their mothers followed healthy practices such as breastfeeding their children and not smoking during and after pregnancy. The standards depict normal human growth under optimal environmental conditions and can be used to assess children everywhere, regardless of ethnicity, socioeconomic status and type of feeding. The standards explicitly identify breastfeeding as the biological norm and establish the breastfed child as the normative model for growth and development. They have the potential to significantly strengthen health policies and public support for breastfeeding. The pooled sample from the 6 participating countries allowed the development of a truly international reference that underscores the fact that child populations grow similarly across the world's major regions when their health and care needs are met. It also provides a tool that is timely and appropriate for the ethnic diversity seen within countries and the evolution toward increasingly multiracial societies in the Americas and Europe as elsewhere in the world. The WHO standards provide a better tool to monitor the rapid and changing rate of growth in early infancy. They also demonstrate that healthy children from around the world who are raised in healthy environments and follow recommended feeding practices have strikingly similar patterns of growth.

Stunting is a major risk factor for overweight: results from national surveys in 5 Arab countries.

We analysed data on overweight and stunting from large national surveys performed between 2001 and 2004 in 5 Arab countries (Djibouti, Libyan Arab Jamahiriya, Morocco, Syrian Arab Republic and Yemen). Overweight and stunting were defined according to new WHO growth standards. Overweight ranged from 8.9% in Yemen to 20.2% in Syrian Arab Republic. The risk ratio (RR) for overweight in stunted children ranged from 2.14 in Djibouti to 3.85 in Libyan Arab Jamahiriya. RR ranged from 0.76 in mildly stunted children of Yemen to 7.15 in severely stunted children in Libyan Arab Jamahiriya. Etiological fraction in the population ranged from 7.49% to 69.76%.

[Body mass index charts of Algerian children and adolescents (6-18 years)]. / Courbes de l'indice de masse corporelle d'enfants et adolescents algériens (6­18 ans).

The body mass index (BMI) is widely accepted as a measure of overweight and obesity in children. There are no BMI reference charts for Algerian children and adolescents. The purpose of this study was to construct BMI percentile curves appropriate for children aged 6-18 years in Algeria. The weight and height of 7772 (54.9% girls) healthy schoolchildren from Constantine (eastern Algeria) were measured in 2008/2009. Weight and height for age curves based on the same sample were published previously. The BMI for age percentile curves were estimated in girls and boys separately using the LMS smoothing method. In both sexes, the median BMI increased with age. Girls had lower BMI values than boys before the age of 10 years but they were higher after this age until 18 years of age. Within the study population, the prevalence of overweight (including obesity) and obesity in girls and boys together was 13.7% and 3.0%, respectively, according to the International Obesity Task Force (IOTF) and 16.9% and 4.9% according to the World Health Organization (WHO) (2007). The median BMI curves of Algerian girls and boys were generally lower than those observed in other Arab countries. Compared with other references, the median BMI values of girls were lower than those of a Belgian Flemish population and WHO 2007 until 14 years of age and higher than the French reference between 7 and 18 years of age. The BMI values of Algerian boys were close to the Belgian (Flemish population), French and WHO 2007 references between 6 and 9 years of age and generally lower thereafter. These BMI curves are complementary to the height and weight charts published previously for the assessment of growth in children and adolescents. They were developed according to international guidelines and could serve as a national reference. They could be used as a complement to the 0- to 5-year-old WHO 2006 standards.

[Weight and height local growth charts of Algerian children and adolescents (6-18 years of age)]. / Courbes de poids et de taille d'enfants et adolescents algériens âgés de 6 à 18 ans.

Measurements of height and weight provide important information on growth and development, puberty, and nutritional status in children and adolescents. The aim of this study was to develop contemporary reference growth centiles for Algerian children and adolescents (6-18 years of age). A cross-sectional growth survey was conducted in government schools on 7772 healthy schoolchildren (45.1% boys and 54.9% girls) aged 6-18 years in Constantine (eastern Algeria) in 2008. Height and weight were measured with portable stadiometers and calibrated scales, respectively. Smooth reference curves of height and weight were estimated with the LMS method. These height and weight curves are presented together with local data from Arab countries and with the growth references of France, Belgium (Flanders), and the World Health Organization (WHO) 2007. In girls, median height and weight increased until 16 and 17 years of age, respectively, whereas in boys, they increased through age 18 years. Between ages 11 and 13 years (puberty), girls were taller and heavier than boys. After puberty, boys became taller than girls, by up to 13 cm by the age of 18 years. Median height and weight of Algerian boys and girls were generally intermediate between those observed in other Arab countries. They were higher than the French reference values up to the age of 13 years and lower than Belgian and WHO reference values at all ages. The present study provides Algerian height- and weight-for-age growth charts, which should be recommended as a national reference for monitoring growth and development in children and adolescents.

Obesity, overweight and thinness in schoolchildren of the city of Florianópolis, Southern Brazil.

OBJECTIVE: To assess the prevalence of obesity, overweight (including obesity) and thinness in children of the city of Florianopolis (southern Brazil). DESIGN: Cross-sectional study. SUBJECTS: Representative sample of 7-10-y-old schoolchildren of the first four grades of elementary schools (1432 girls, 1504 boys). METHODS: Measurements of weight, height and triceps skinfold thickness (TSF) were taken following standard techniques. The body mass index (BMI) was computed as weight/height2. Nutritional status was defined using two references: (1) the Must et al reference for BMI and TSF to define thinness, overweight and obesity (5th, 85th and 95th percentiles, respectively); (2) the International Obesity Task Force (IOTF) BMI cutoffs to define overweight and obesity. RESULTS: Using BMI, according to the Must et al, and IOTF references, the prevalence of obesity was 10.6 and 5.5%, respectively; overweight (including obesity) affected 26.2 and 22.1% of children, respectively. According to the Must et al reference, the prevalence of thinness was 3.2%. Using TSF rather than BMI, according to the Must et al references, fewer children were classified as obese (8.0%) or overweight (20.2%) and more children were classified as thin (4.9%). CONCLUSION: This study supports the previously reported high frequencies of childhood overweight and obesity in developing countries. The data allow comparisons with other studies carried out in Brazil and other parts of the world.

No correlation between adiposity and food intake: why are working class children fatter?

Many studies have failed to show a correlation between individual energy intake and obesity. However, the prevalence of overweight is higher in populations with higher caloric intake. In this study on a population of French children, no correlation was found between energy intake and individual corpulence (wt/ht2 index or skinfold thickness), but a higher proportion of overweight children was found in lower social classes where energy intake is traditionally higher. A hypothesis is proposed to account for this apparent contradiction: the typical lifestyle or diet in a given population challenges individual adaptive capacities; the more caloric the socially accepted diet, the higher the proportion of individuals who are challenged beyond their adaptive threshold. Socially determined factors such as a high calorie diet act in a permissive way in the development of obesity although the caloric intake of obese individuals may be no different from that of nonobese peers.

Adiposity indices in children.

On the basis of a longitudinal study of growth in French children, we attempted to find a valid index for estimating adiposity, and to specify the optimal conditions for its use. The Quetelet index was found suitable for application to children, but as with all methods, a certain lack of precision proved unavoidable because of the different stages of growth observed at a given age. For use by clinicians, we provide charts, based on the Quetelet index and on age, permitting estimation of adiposity in any child on the basis of longitudinal study measurements. For use by epidemiologists, we give standard values for studying groups of subjects, even when a reference population is not available. Body adiposity may be expressed independently of age and sex.

Adiposity rebound in children: a simple indicator for predicting obesity.

To follow and predict the evolution of adiposity during growth, individual adiposity curves, assessed by the weight/height2 index, were drawn for 151 children from the age of 1 month to 16 yr. Adiposity increases during the 1st yr and then decreases. A renewed rise, termed here the adiposity rebound, occurs at about 6 yr. Individual weight/height2 curves may differ regarding their percentile range level and age at adiposity rebound. The present study shows a relationship between the age at adiposity rebound and final adiposity. An early rebound (before 5.5 yr) is followed by a significantly higher adiposity level than a later rebound (after 7 yr). This phenomenon is observed whatever the subject's adiposity at 1 yr. The present observations might be connected with the cellularity of adipose tissue.

Body composition assessed on the basis of arm circumference and triceps skinfold thickness: a new index validated in children by magnetic resonance imaging.

Fat and muscle areas can be calculated from equations on the basis of upper arm circumference (C) and triceps skinfold thickness (TS). These equations assume a circular limb and muscle compartment and a symmetrically distributed fat rim: total upper arm area (TUA) = C2/(4 pi), upper arm muscle area (UMA) = [C - (TS x pi)2]/(4 pi), and upper arm fat area (UFA) = TUA - UMA. This traditional method underestimates the degree of adiposity. We propose that the unrolled fat rim is a rectangle whose length = C and width = TS/2. The following new indexes are based on this assumption: upper arm fat area estimate (UFE) = C x (TS/2), and upper arm muscle area estimate (UME) = TUA - UFE. To validate these equations, areas were measured with magnetic resonance imaging (MRI) in 28 children aged 9-15 y (17 control subjects and 11 obese subjects). Correlations between MRI and UFA and MRI and UFE were similar (r = 0.96 for both correlations in the control group and r = 0.84 and 0.82, respectively, in the obese group), but the areas assessed by MRI (13.8 cm2) were closer to UFE (12.4 cm2) than to UFA (11.2 cm2) in the control group as well as in the obese group (MRI = 48.7 cm2, UFE = 46.6 cm2, and UFA = 38.5 cm2). The limits of agreement between MRI and anthropometry were 5.7 +/- 5.8 cm2 for UFA and 0.6 +/- 5.0 cm2 for UFE, showing that UFA is not acceptable in most cases, whereas UFE measurements are close to MRI measurements. In conclusion, UFE and UME are simple and accurate indexes to assess body composition. French reference values are available from 1 mo to 17 y of age.

Relationship between adiposity and food intake: an example of pseudo-contradictory results obtained in case-control versus between-populations studies.

Seemingly contradictory data support controversies concerning the relationships between food intake and illnesses. The present study of 1035 adults, aged 30-39 years, shows that (1) daily energy intake is not higher in obese than in non-obese people, (2) obesity is more prevalent in social groups where energy intake is higher. These pseudo-contradictory results can be reconciled on the basis of a constitution/environment interaction. A comparison of groups based on presence or absence of illness (obesity, hypertension, coronary heart disease (CHD), cancer, etc) shows that some people can develop risk factors, even though their feeding behaviour is normal. This result (no direct relationship) underlines differences in individual susceptibility. When comparisons are made between populations with different diets the results (direct relationship) express environmental factors. The hypotheses on behavioural contribution to the aetiology of certain diseases appears more clearly in between-population comparisons than in case-control studies. Results of comparisons between populations (if the hypotheses they suggest are confirmed by intervention studies) warrant prevention at the level of populations, while results of case-control studies justify particular prevention in subjects at risk.

Individual patterns of food intake development in children: a 10 months to 8 years of age follow-up study of nutrition and growth.

Individual patterns of food intake development have been investigated on the basis of a longitudinal study of nutrition and growth carried out in 112 children at the ages of 10 months, and 2, 4, 6, and 8 years. On the average, energy intake increased steadily with age. However, individual subjects sometimes followed a different pattern. Approximately 1 out of 5 subjects decreased their intake between two examinations. Besides, less than half the children (43%) were in the same category of energy intake (defined as tertiles) at 10 months and 8 years of age. Similarly, 47% of the children were in the same weight/height (BMI) category at 10 months and 8 years. Correlations computed between early intakes (10 months, and 2, 4, and 6 years) and intakes at 8 years were better for energy and protein intake than for fat and carbohydrates (CHO), showing that intake of energy or protein early in life has a better predictive value of intake at later ages. Energy intake development has been examined in those children who were found to be lean, medium, and fat at the age of 8 years; it increased more between the ages of 4 and 6 years, in children who were fat at 8 years. Individual variations of anthropometric measurements during growth are well documented. The present study points out that similar individual variations of intake also exists. These variations could reflect regulatory processes acting during growth and should be taken into account in investigating the child's appetite.

Nutritional status and food intake in adolescents living in Western Europe.

This review covers surveys of nutritional intake in adolescents living in several countries of Western Europe. Current definitions of nutritional status are discussed, with a special emphasis on adolescent years. It is generally observed that obesity rates are increasing (especially those of massive obesity) in young people, whereas declared energy intakes are decreasing. Average daily energy input seems adequate in adolescents of Western Europe. However, fat (especially saturated) intake is high while that of CHO and fiber is low. Proteins are mainly (two-thirds) from animal sources. Average micronutrient intakes correspond to recommended values in most cases, but there are a few exceptions (calcium and iron) that are low, particularly in girls. Specific problems become frequent at adolescence, such as dieting, smoking, getting low quality foods away from the home, etc. These behaviors may induce adverse nutritional conditions. On average, nutritional problems at adolescence do not appear to be more severe than at other ages, however they may exert a strong deleterious impact on future health.

Body Mass Index variations: centiles from birth to 87 years.

This report provides Body Mass Index (weight/height2) values for the French population from birth to the age of 87 years. BMI curves increase during the first year, decrease until the age of 6, increase again up to 65 years and decrease thereafter. These variations reflect the total changes of fat body mass during life. The 50th centile values of Wt/Ht2 at the ages of 20, 40, 60, 80 years are 21.5, 24.6, 25.4, 24.4 kg/m2 for men and 20.6, 22.6, 24.1, 23.4 kg/m2 for women. The values for the 3rd, 50th and 97th centiles in the middle years are approximately 18, 24 and 32 kg/m2. Graphs for these and four other percentiles are plotted against age, and two other graphs summarising the variation and skewness of the Wt/Ht2 distribution are provided to calculate exact percentiles and Z-scores for individuals.

The anabolic steroid oxandrolone increases muscle mass in prepubertal boys with constitutional delay of growth.

The aim of this study was to investigate the effect of oxandrolone on body composition in boys with constitutional delay of growth and puberty. In 14 prepubertal boys, height, weight, triceps and subscapular skinfolds and upper arm circumference were measured. Body mass index, the ratio of subscapular to triceps skinfolds and the upper muscle area were also determined. The difference of the various measurements and indices, 3 to 6 months before and after commencement of oxandrolone treatment, were calculated, while the boys remained prepubertal. We observed a marked increase in body mass index, a decrease of triceps and subscapular skinfolds, an increase in the ratio of subscapular to triceps skinfolds and also an increase in upper muscle area after the onset of oxandrolone treatment. These results suggest that low dose oxandrolone administration in prepubertal boys with constitutional growth delay causes a disproportionate increase of weight to height which is largely due to increased body muscle.