Macronutrient energy intake and adiposity in non obese prepubertal children aged 5-11 y (the Fleurbaix Laventie Ville Santé Study)

Energy intakes, macronutrient intakes and the percentages of energy from macronutrients with adolescent BMI: results from a 5-year cohort study in Ho Chi Minh City, Vietnam

BACKGROUND

Adolescence is a period of life when dietary patterns and nutrient intakes may greatly influence adult fatness. This study assesses the tracking of energy and nutrient intakes of Ho Chi Minh City adolescents over 5 years. It explores the possible relationships between energy and the percentage of energy from macronutrients with BMI.

METHODS

Height, weight, time spent on physical activity, screen time and dietary intakes were collected annually between 2004 and 2009 among 752 junior high school students with a mean age of 11·87 years at baseline. The tracking was investigated using correlation coefficients and weighted kappa statistics (k) for repeated measurements. Mixed effect models were used to investigate the association between energy intakes and percentage energy from macronutrients with BMI.

RESULTS

There were increases in the mean BMI annually, but greater in boys than in girls. Correlation coefficients (0·2 < r < 0·4) between participants' intakes at baseline and 5-year follow-up suggest moderate tracking. Extended kappa values were lowest for energy from carbohydrate (CHO) in both girls and boys (k = 0·18 & 0·24, respectively), and highest for protein in girls (k = 0·47) and fat in boys (k = 0·48). The multilevel models showed the following variables significantly correlated with BMI: CHO, fat, percentage of energy from CHO, fat, time spent for moderate to vigorous physical activity, screen time, age and sex.

CONCLUSIONS

The poor to fair tracking observed in this cohort suggests that individual dietary patterns exhibited in the first year are unlikely to predict energy and nutrient intakes in the fifth year.

Prevalence of overweight among Dutch primary school children living in JOGG and non-JOGG areas

Background

One of the most influential integrated approaches towards reducing childhood obesity is EPODE, a program that has been translated to over 20 different countries worldwide.

Aim

The goal of this study was to explore how JOGG–the Dutch EPODE adaptation–might reduce overweight prevalence among children.

Methods

To compare whether overweight prevalence was different in JOGG areas vs. non-JOGG areas, in long-term JOGG areas vs. short-term JOGG areas, and in low SES JOGG areas vs. middle/high SES JOGG areas, secondary anthropometric and personal data of 209,565 Dutch children were mapped onto publicly available JOGG data.

Results

Findings showed that overweight prevalence decreased from 25.17% to 16.08% in JOGG-areas, and from 32.31% to 18.43% in long-term JOGG areas. However, when taking into account SES, the decrease in prevalence was mainly visible in low SES long-term JOGG areas.

Conclusion

JOGG appeared to be successful in targeting areas where overweight was most prevalent. Low SES areas that had implemented JOGG for a longer period of time, i.e., six years, appeared to be successful in decreasing overweight prevalence.

Assessment of selected nutrient intake by Polish preschool children compared to dietary recommendations: a meta-analysis

INTRODUCTION

In recent years a steady increase in the number of obese people has been observed worldwide. This problem is also increasingly applicable to children and adolescents. In this study, we conducted a meta-analysis of studies carried out in Poland over ten years (2005-2015) which analysed the diet of preschool children and assessed how significantly it affects the prevention of diet-dependent disease.

MATERIAL AND METHODS

Two of the researchers independently performed a systematic search of Medline, Embase, Google Scholar, and the Polish Medical Bibliography to find studies published between 2005 and 2015. The variance of the means of differences between selected factors in relation to dietary guidelines and standards for preschool children was estimated by summing the individual variances of means. The means of differences between selected factors across the studies were pooled using random-effects model meta-analysis.

RESULTS

The analysis included a total of 2095 children. Mean protein content in the diet of children studied is 111% higher than indicated in dietary recommendations for this age group; mean consumption of carbohydrates in the study group is 24% higher than recommended. In moderately high calorie diets, analysis showed that the recommended norm is exceeded by 47%, CE 0.77, p < 0.001.

CONCLUSIONS

Nutrient intake is not compliant with recommendations for this age group and could not only inhibit physical development, but also increase the risk of diet-dependent diseases.

Associations of sugar intake with anthropometrics in children from ages 2 until 8 years in the EU Childhood Obesity Project

PURPOSE

We determined the association of total sugar intake with body weight and fat mass in children on an energy-equivalent basis and potential changes in the association from 2 to 8 years of age.

METHODS

Data were available from the Childhood Obesity Project Trial initiated in 2002. Sugar intake was measured by 3-day weighed food protocols at 2, 3, 4, 5, 6, and 8 years of age. Body mass index (BMI) and fat mass index (FMI) were available at the same time points. To investigate the association of sugar intake with anthropometrics over time, linear mixed models were applied. Odds ratios for having a high BMI or FMI (above one standard deviation) were estimated by logistic random-effects models. To control for total energy intake, the residual method was chosen and models were additionally adjusted for total energy intake.

RESULTS

Data were available for 809 children with in total 2846 observations. In an isocaloric model, an increase of 100 kcal from sugar per day was significantly associated with lower zBMI (- 0.033; 95% CI -0.061, - 0.005) and zFMI (- 0.050; 95% CI - 0.089, - 0.011). In addition, a 100 kcal higher sugar intake was related to lower odds of having a high zBMI (OR 0.743; 95% CI 0.611, 0.903).

CONCLUSION

This study provides no indication that increased total sugar intake positively affects BMI on an energy-equivalent basis. Whether the negative association of sugar is due to physiological effects or points more to macronutrient preferences or a reporting bias (lower sugar intake) in children with higher BMI can be debated.

CLINICAL TRIAL REGISTRY

ClinicalTrials.gov Identifier: NCT00338689; Registered: June 19, 2006. URL: http://clinicaltrials.gov/ct2/show/NCT00338689?term=NCT00338689&rank=1 .

Should the WHO growth charts be used in France?

BACKGROUND

Growth charts are an essential clinical tool for evaluating a child's health and development. The current French reference curves, published in 1979, have recently been challenged by the 2006 World Health Organization (WHO) growth charts.

OBJECTIVE

To evaluate and compare the growth of French children who were born between 1981 and 2007, with the WHO growth charts and the French reference curves currently used.

DESIGN

Anthropometric measurements from French children, who participated in 12 studies, were analyzed: 82,151 measurements were available for 27,257 children in different age groups, from birth to 18 years. We calculated and graphically compared mean z-scores based on the WHO and French curves, for height, weight and Body Mass Index (BMI) according to age and sex. The prevalence of overweight using the WHO, the French and International Obesity Task Force definitions were compared.

RESULTS

Our population of children was on average 0.5 standard deviations taller than the French reference population, from the first month of life until puberty age. Mean z-scores for height, weight and BMI were closer to zero based on the WHO growth charts than on the French references from infancy until late adolescence, except during the first six months. These differences not related to breastfeeding rates. As expected, the prevalence of overweight depended on the reference used, and differences varied according to age.

CONCLUSION

The WHO growth charts may be appropriate for monitoring growth of French children, as the growth patterns in our large population of French children were closer to the WHO growth charts than to the French reference curves, from 6 months onwards. However, there were some limitations in the use of these WHO growth charts, and further investigation is needed.

Usual energy and macronutrient intakes in 2-9-year-old European children

OBJECTIVE

Valid estimates of population intakes are essential for monitoring trends as well as for nutritional interventions, but such data are rare in young children. In particular, the problem of misreporting in dietary data is usually not accounted for. Therefore, this study aims to provide accurate estimates of intake distributions in European children.

DESIGN

Cross-sectional setting-based multi-centre study.

SUBJECTS

A total of 9560 children aged 2-9 years from eight European countries with at least one 24-h dietary recall (24-HDR).

METHODS

The 24-HDRs were classified in three reporting groups based on age- and sex-specific Goldberg cutoffs (underreports, plausible reports, overreports). Only plausible reports were considered in the final analysis (N=8611 children). The National Cancer Institute (NCI)-Method was applied to estimate population distributions of usual intakes correcting for the variance inflation in short-term dietary data.

RESULTS

The prevalence of underreporting (9.5%) was higher compared with overreporting (3.4%). Exclusion of misreports resulted in a shift of the energy and absolute macronutrient intake distributions to the right, and further led to the exclusion of extreme values, that is, mean values and lower percentiles increased, whereas upper percentiles decreased. The distributions of relative macronutrient intakes (% energy intake from fat/carbohydrates/proteins) remained almost unchanged when excluding misreports. Application of the NCI-Method resulted in markedly narrower intake distributions compared with estimates based on single 24-HDRs. Mean percentages of usual energy intake from fat, carbohydrates and proteins were 32.2, 52.1 and 15.7%, respectively, suggesting the majority of European children are complying with common macronutrient intake recommendations. In contrast, total water intake (mean: 1216.7 ml per day) lay below the recommended value for >90% of the children.

CONCLUSION

This study provides recent estimates of intake distributions of European children correcting for misreporting as well as for the daily variation in dietary data. These data may help to assess the adequacy of young children's diets in Europe.

Dietary intake in 6-year-old children from southern Poland: part 1--energy and macronutrient intakes

Background

The studies on dietary intake in Polish children are sparse and the information about dietary intake in 6-year-olds in Europe is limited. The published studies on dietary intake in children rarely provide information on the intake of animal protein, plant protein and water. The purpose of the study was to analyse energy and macronutrient intakes in 6-year-old children from southern Poland.

Methods

The studied population comprised 120 children, 64 girls and 56 boys. Energy and macronutrient intakes were estimated from a three-day food record. Weight and height were measured, and body mass index was calculated.

Results

Intakes of energy (kJ, kcal), plant protein (g), total fat (g), saturated fatty acids (g, % of energy, g/1000 kcal), monounsaturated fatty acids (g) and starch (g, % of energy, g/1000 kcal) were significantly higher in boys, while intakes of sucrose (% of energy, g/1000 kcal) and total water (g/1000 kcal) were significantly higher in girls. The children’s diets were characterised by excessive intake of total fat, saturated fatty acids, sucrose, and by inadequate intake of polyunsaturated fatty acids, available carbohydrates and starch.

Conclusions

The observed adverse characteristics of the children’s diets are similar to those observed in the diets of children in other European countries and show the need to work out a common educational programme to improve nutrition in young European children. It is also important to provide the lacking information about the intake of animal protein, plant protein and water in young children.

Animal protein intake at 12 months is associated with growth factors at the age of six

AIM

To study the associations between protein intake from different sources with anthropometry and serum insulin-like growth factor 1 (IGF-1) in infancy and childhood.

METHODS

Children (n = 199) born in Iceland were followed up to six years of age. Their intake of various animal proteins and vegetable protein was calculated from weighed food records at 12 months and 6 years. Information about their weight and height at birth, 12 and 18 months, and 6 years was gathered. Serum IGF-1 was measured at 12 months and 6 years.

RESULTS

At the age of six, children in the highest quartile for animal protein intake at 12 months (≥12.2% of total energy) had 0.8 kg/m(2) (95% CI = 0.1, 1.5) higher body mass index (BMI) than children in the lowest quartile (<7.6% of total energy). They were also heavier and longer in infancy and childhood. At 12 months, dairy protein intake as a percentage of total energy was associated with IGF-1 in six-year-old girls, β = 5.4 μg/L (95% CI = 2.5, 8.2).

CONCLUSION

High animal protein intake in infancy, but not vegetable protein intake, was associated with accelerated growth and higher BMI in childhood. Dairy protein intake in infancy may be positively associated with linear growth and also with IGF-1 in six-year-old girls.

High fat diets are associated with higher abdominal adiposity regardless of physical activity in adolescents; the HELENA study

BACKGROUND & AIMS

Failure to attain fat balance may contribute to obesity development even without excessive energy intake. The objective of this study was to examine the associations of dietary macronutrient distribution with abdominal adiposity in adolescents and to evaluate whether these relationships were attenuated by physical activity.

METHODS

A total of 224 Spanish adolescents (51% females, 14.9 ± 1.2 years) were included in the study. Abdominal adiposity in three regions, truncal and total body fat mass (FM) and lean mass (LM) were measured by dual-energy X-ray absorptiometry and thereafter FM index (FMI = FM/height(2)) and FMI/LMI ratio were calculated. The energy derived from fat intake was assessed by two non-consecutive 24 h recalls. Total physical activity (PA) and time spent in moderate-to-vigorous PA (MVPA) and vigorous PA were objectively measured by accelerometry.

RESULTS

We observed that the percent of energy derived from fat intake was significantly associated with FMI and FMI/LMI ratio (Ps = 0.001) and greater amounts of truncal (P = 0.001) and abdominal adiposity in the three regions regardless of age, sex and height (all P ≤ 0.005). The strength of the relationships was not substantially altered by further adjustment for PA, vigorous PA or moderate-to-vigorous PA (Ps ≤ 0.005).

CONCLUSIONS

The percent of energy derived from dietary fat intake is strongly and linearly associated with total, truncal and abdominal adiposity independently of PA in adolescents. These observations implicate the amount of dietary fat intake as a specific risk factor in the excess of abdominal adiposity in adolescence.

Protein intake from 0 to 18 years of age and its relation to health: a systematic literature review for the 5th Nordic Nutrition Recommendations

The present systematic literature review is a part of the 5th revision of the Nordic Nutrition Recommendations. The aim was to assess the health effects of different levels of protein intake in infancy and childhood in a Nordic setting. The initial literature search resulted in 435 abstracts, and 219 papers were identified as potentially relevant. Full paper selection resulted in 37 quality-assessed papers (4A, 30B, and 3C). A complementary search found four additional papers (all graded B). The evidence was classified as convincing, probable, limited-suggestive, and limited-inconclusive. Higher protein intake in infancy and early childhood is convincingly associated with increased growth and higher body mass index in childhood. The first 2 years of life is likely most sensitive to high protein intake. Protein intake between 15 E% and 20 E% in early childhood has been associated with an increased risk of being overweight later in life, but the exact level of protein intake above which there is an increased risk for being overweight later in life is yet to be established. Increased intake of animal protein in childhood is probably related to earlier puberty. There was limited-suggestive evidence that intake of animal protein, especially from dairy, has a stronger association with growth than vegetable protein. The evidence was limited-suggestive for a positive association between total protein intake and bone mineral content and/or other bone variables in childhood and adolescence. Regarding other outcomes, there were too few published studies to enable any conclusions. In conclusion, the intake of protein among children in the Nordic countries is high and may contribute to increased risk of later obesity. The upper level of a healthy intake is yet to be firmly established. In the meantime, we suggest a mean intake of 15 E% as an upper limit of recommended intake at 12 months, as a higher intake may contribute to increased risk for later obesity.

VNTR Polymorphism of the Insulin Gene and Childhood Overweight in a General Population

OBJECTIVE

The VNTR polymorphism 5' of the insulin gene has been related to obesity in a previous study on children with early onset of severe obesity. Our purpose was to analyze the association between this polymorphism and adiposity variability in an unselected population of children and adolescents in northern France.

RESEARCH METHODS AND PROCEDURES

In 293 nuclear families from the Fleurbaix Laventie Ville Santé study, we genotyped the INS VNTR polymorphism in 431 children and adolescents (8 to 18 years of age) and their parents. Overweight was defined according to the international definition in both children and adults. A transmission disequilibrium test in families with an overweight offspring was performed. The prevalence of overweight was compared according to genotype. The effect of the genotype on BMI and waist circumference was tested with a linear regression model, adjusting for age, gender, and Tanner stage.

RESULTS

There was an undertransmission of class III alleles from heterozygous parents to their overweight offspring (p < 0.002). Overweight was associated with class I alleles in children and adolescents (12% I/I, I/III vs. 3% III/III; p < 0.08). Those with a class III/III genotype had a 1 kg/m(2) lower mean BMI (p = 0.04) and 3 cm lower waist circumference (p = 0.02) than those bearing one or two class I alleles. No association of adiposity or obesity with class I alleles was found in parents.

DISCUSSION

INS VNTR polymorphism seems to contribute to differences in adiposity level in the general population of children and adolescents.

Fructose toxicity: is the science ready for public health actions?

PURPOSE OF REVIEW

The assumption that fructose may be toxic and involved in the pathogenesis of noncommunicable diseases such as obesity, diabetes mellitus, dyslipidemia, and even cancer has resulted in the call for public health action, such as introducing taxes on sweetened beverages. This review evaluates the scientific basis for such action.

RECENT FINDINGS

Although some studies hint towards some potential adverse effects of excessive fructose consumption especially when combined with excess energy intake, the results from clinical trials do not support a significant detrimental effect of fructose on metabolic health when consumed as part of a weight-maintaining diet in amounts consistent with the average-estimated fructose consumption in Western countries. However, definitive studies are missing.

SUMMARY

Public health policies to eliminate or limit fructose in the diet should be considered premature. Instead, efforts should be made to promote a healthy lifestyle that includes physical activity and nutritious foods while avoiding intake of excess calories until solid evidence to support action against fructose is available. Public health is almost certainly to benefit more from policies that are aimed at promoting what is known to be good than from policies that are prohibiting what is not (yet) known to be bad.

Dietary factors associated with overweight and body adiposity in Finnish children aged 6-8 years: the PANIC Study

OBJECTIVES

To investigate the associations of dietary factors with overweight, body fat percentage (BF%), waist circumference (WC) and hip circumference (HC) among children.

DESIGN

Cross-sectional analysis of the Physical Activity and Nutrition in Children (PANIC) Study among 510 children (263 boys, 247 girls) aged 6-8 years from Kuopio, Finland.

METHODS

The children's weight, height, WC and HC were measured. Overweight was defined by International Obesity Task Force body mass index cutoffs. The BF% was measured by dual-energy X-ray absorptiometry, nutrient intakes and meal frequency by 4-day food records and eating behaviour by Children's Eating Behaviour Questionnaire.

RESULTS

Daily consumption of all the three main meals was inversely associated with overweight (odds ratio (OR) 0.37, 95% confidence interval (CI) 0.18-0.75), BF% (β -0.12, P = 0.012), WC (β -0.16, P = 0.002) and HC (β -0.15, P = 0.002). Enjoyment of food, food responsiveness and emotional overeating were directly associated with overweight (OR 1.57, 95% CI 1.04-2.35; OR 4.68, 95% CI 2.90-7.54; OR 2.60, 95% CI 1.52-4.45, respectively), BF% (β 0.13, P = 0.004; β 0.30, P<0.001; β 0.09, P = 0.035, respectively), WC (β 0.14, P = 0.003; β 0.40, P<0.001; β 0.19, P<0.001, respectively) and HC (β 0.15, P = 0.001; β 0.38, P<0.001; β 0.15, P = 0.001, respectively). Satiety responsiveness was inversely associated with overweight (OR 0.42, 95% CI 0.26-0.67), BF% (β -0.20, P<0.001), WC (β -0.26, P<0.001) and HC (β -0.26, P<0.001). Slowness in eating was inversely associated with overweight (OR 0.61, 95% CI 0.41-0.92), WC (β -0.16, P = 0.001) and HC (β -0.17, P<0.001). Protein intake was directly associated with BF% (β 0.11, P = 0.017), WC (β 0.11, P = 0.020) and HC (β 0.13, P = 0.008).

CONCLUSIONS

Promoting regular consumption of main meals and healthy eating behaviours should be emphasized in the prevention of overweight among children. More research is needed on the association of protein-rich foods with body adiposity in children.

Family food behaviours and adolescents' overweight status: a mother-offspring link study

BACKGROUND

The role of family food behaviours on weight status of family members is not well understood. The objective of this study was to examine the influence of some aspects of family food behaviours on adolescents overweight.

METHOD

In a cross-sectional mother-child-linked study design, participants were a subsample of 3862 adolescents (51.9% boys) from the Mater hospital-University of Queensland Study of Pregnancy (MUSP), a longitudinal study of a birth cohort of 7,223 women and their offspring. Information on aspects of family food behaviours (family meal patterns and influences, frequency of family food consumption, and influences on family food selection) was collected by self reported questionnaires from mothers in a 14 years follow up (in 1994-1997) and other covariates at different stages of follow-ups. Body Mass Index of the adolescents was calculated using measured height and weight.

RESULTS

Being overweight at 14 years had significant negative associations with mothers' report on the importance of family meals (OR=1.28), frequency of eating cake/biscuits (OR=1.71), and significant positive association with mothers' report on frequency of consumption of cooked vegetables (OR=1.32), soft drinks (OR=1.60) and importance of fattening of foods (OR=1.27).

CONCLUSION

The study confirmed the importance of the family and some family food behaviours in shaping risk of being overweight amongst adolescents. Because of the cross-sectional nature of this study, we could not conclude that they had casual correlations. Comparison with the literature suggests that some of these effects may be specific to particular contexts, potentially affected by cultural and socio-economic differences.

Associations of body mass index and waist circumference with: energy intake and percentage energy from macronutrients, in a cohort of Australian children

Background

It is evident from previous research that the role of dietary composition in relation to the development of childhood obesity remains inconclusive. Several studies investigating the relationship between body mass index (BMI), waist circumference (WC) and/or skin fold measurements with energy intake have suggested that the macronutrient composition of the diet (protein, carbohydrate, fat) may play an important contributing role to obesity in childhood as it does in adults. This study investigated the possible relationship between BMI and WC with energy intake and percentage energy intake from macronutrients in Australian children and adolescents.

Methods

Height, weight and WC measurements, along with 24 h food and drink records (FDR) intake data were collected from 2460 boys and girls aged 5-17 years living in the state of Queensland, Australia.

Results

Statistically significant, yet weak correlations between BMI z-score and WC with total energy intake were observed in grades 1, 5 and 10, with only 55% of subjects having a physiologically plausible 24 hr FDR. Using Pearson correlations to examine the relationship between BMI and WC with energy intake and percentage macronutrient intake, no significant correlations were observed between BMI z-score or WC and percentage energy intake from protein, carbohydrate or fat. One way ANOVAs showed that although those with a higher BMI z-score or WC consumed significantly more energy than their lean counterparts.

Conclusion

No evidence of an association between percentage macronutrient intake and BMI or WC was found. Evidently, more robust longitudinal studies are needed to elucidate the relationship linking obesity and dietary intake.

Analysis of the SIM1 contribution to polygenic obesity in the French population

SIM1 (single-minded 1) haploinsufficiency is responsible for obesity in both humans and mice, but the contribution of frequent DNA variation to polygenic obesity is unknown. Sequencing of all exons, exon/intron boundaries, 870 base pairs (bp) of the putative promoter, and 1,095 bp of the 3'UTR of SIM1 gene in 143 obese children and 24 control adults identified 13 common variants. After analysis of the linkage disequilibrium (LD) structure, association study of eight variants was performed in 1,275 obese children and severely obese adults, in 1,395 control subjects, and in 578 obesity-selected pedigrees. A nominal evidence of association was found for the nonsynonymous variant P352T C/A (rs3734354) (P = 0.01, OR = 0.81 (0.70-0.95)), the +2,004 TGA -/insT SNP (rs35180395) (P = 0.02, OR = 1.21 (1.02-1.43)), the +2,215A/G TGA SNP (rs9386126) (P = 0.002, OR = 0.81 (0.71-0.93)), and pooled childhood/adult obesity. Even though transmission disequilibrium test (TDT) further supported the association of P352T and +2,004 -/inst T with obesity, none of these nominal associations remained significant after a multiple testing Bonferroni correction. Therefore, our study excludes a major contribution of SIM1 common variants in exons, 5' and 3' UTR regions in polygenic obesity susceptibility in French Europeans.

Parental body size and early weight and height growth velocities in their offspring

BACKGROUND

Whereas weight or height at a given age are the results of the cumulative growth experience, growth velocities allows the study of factors affecting growth at given ages.

AIM

To study the relationships between parental height and body mass index (BMI) and offspring's height and weight growth during infancy and childhood.

STUDY DESIGN

From the FLVSII population-based study, 235 parent-child trios belonging to 162 families examined in 1999.

OUTCOME MEASURES

From medical records and previous FLVS examinations, child's height and weight history were reconstructed. Weight and height growth velocities from birth to seven years were estimated from a modelling of individual growth curve and correlated with parent's body size in 1999.

RESULTS

Ponderal index and length at birth were significantly associated with maternal but not paternal BMI and height. In the first six months, height growth velocity was significantly associated with maternal stature (at three months: 0.12+/-0.05 and 0.02+/-0.05 cm/month for a 10 cm difference in maternal and paternal height respectively) and weight growth velocity with paternal BMI (at three months: 5.7+/-2.8 and 1.9+/-2.3g/month for a difference of 1 kg/m(2) in paternal and maternal BMI respectively). Between two and five years, height growth velocity was more significantly associated with paternal height whereas weight growth velocity was more closely associated with maternal BMI.

CONCLUSIONS

Early childhood growth is characterised by alternate periods associated specifically with maternal or paternal BMI and height. This novel finding should trigger the search for specific genetic, epigenetic or environmentally shared factors from the mothers and fathers.

Early detrimental metabolic outcomes of rs17300539-A allele of ADIPOQ gene despite higher adiponectinemia

Minor allele A of single-nucleotide polymorphism (SNP) 11391 G/A of ADIPOQ gene (rs17300539) has been consistently associated with higher adiponectin levels in adults and children. The aim of this study was to investigate the metabolic role of this variant in a large cohort of children of European origin. A total of 1,852 children from two general populations in Verona and in Fleurbaix-Laventie and from the Lille childhood obesity cohort, were genotyped and pooled together after checking for the absence of genetic heterogeneity for rs17300539 between Italian and French children. The genotype of rs17300539 was studied in relation to circulating adiponectin levels, BMI, fasting plasma glucose, fasting serum insulin (FSI), insulin resistance index (homeostasis model assessment of insulin resistance (HOMA(IR))), high-density lipoprotein cholesterol, and triglycerides. After adjustment for known confounders, rs17300539 GA+AA carriers had 1.6 microg/ml higher adiponectin levels (P = 6 x 10(-8)) than GG carriers. They also showed higher BMI (B = 0.97, P = 0.015) and higher prevalence of obesity (OR = 1.35 (1.06-1.85), P = 0.015) than GG carriers. Before adjusting for obesity status, GA+AA carriers had higher FSI (B = 1.10, P = 0.040) and higher HOMA(IR) (B = 0.31, P = 0.020) than GG carriers. After adjustment for obesity status, they did not differ from GG carriers for any metabolic parameter, either among obese or nonobese children. The rs17300539-A variant, though consistently associated with higher adiponectin levels, does not exert any appreciable protective metabolic effect in children, either in the presence or absence of obesity. In contrast, this SNP may increase the risk for childhood obesity and related insulin resistance.

Dietary intakes and food sources of fat and fatty acids in Guatemalan schoolchildren: a cross-sectional study

BACKGROUND

Consumption of healthy diets that contribute with adequate amounts of fat and fatty acids is needed for children. Among Guatemalan children, there is little information about fat intakes. Therefore, the present study sought to assess intakes of dietary fats and examine food sources of those fats in Guatemalan children.

METHODS

The study subjects consisted of a convenience sample of 449 third- and fourth-grade schoolchildren (8-10 y), attending public or private schools in Quetzaltenango City, Guatemala. Dietary data was obtained by means of a single pictorial 24-h record.

RESULTS

The percentages of total energy (%E) from total fat, saturated fat (SFA) and monounsaturated fat (MUFA) reached 29%E for total fat and 10%E for each SFA and MUFA, without gender differences. %E from fats in high vs. low-socio economic status (SES) children were significantly higher for boys, but not for girls, for total fat (p = 0.002) and SFA (p < 0.001). Large proportions of the children had low levels of intakes of some fatty acids (FA), particularly for n-3 FA, with >97% of all groups consuming less than 1%E from this fats. Fried eggs, sweet rolls, whole milk and cheese were main sources of total fat and, SFA. Whole milk and sweet bread were important sources of n-3 FA for high- and low-SES boys and girls, respectively. Fried plantain was the main source of n-3 FA for girls in the high-SES group. Fried fish, seafood soup, and shrimp, consumed only by boys in low amounts, were sources of eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids, which may explain the low intakes of these nutrients.

CONCLUSIONS

alpha-linolenic acid, EPA and DHA were the most limiting fatty acids in diets of Guatemalan schoolchildren, which could be partially explained by the low consumption of sources of these nutrients, particularly fish and seafood (for EPA and DHA). This population will benefit from a higher consumption of culturally acceptable foods that are rich in these limiting nutrients.

Metabolic effects of fructose and the worldwide increase in obesity

While virtually absent in our diet a few hundred years ago, fructose has now become a major constituent of our modern diet. Our main sources of fructose are sucrose from beet or cane, high fructose corn syrup, fruits, and honey. Fructose has the same chemical formula as glucose (C(6)H(12)O(6)), but its metabolism differs markedly from that of glucose due to its almost complete hepatic extraction and rapid hepatic conversion into glucose, glycogen, lactate, and fat. Fructose was initially thought to be advisable for patients with diabetes due to its low glycemic index. However, chronically high consumption of fructose in rodents leads to hepatic and extrahepatic insulin resistance, obesity, type 2 diabetes mellitus, and high blood pressure. The evidence is less compelling in humans, but high fructose intake has indeed been shown to cause dyslipidemia and to impair hepatic insulin sensitivity. Hepatic de novo lipogenesis and lipotoxicity, oxidative stress, and hyperuricemia have all been proposed as mechanisms responsible for these adverse metabolic effects of fructose. Although there is compelling evidence that very high fructose intake can have deleterious metabolic effects in humans as in rodents, the role of fructose in the development of the current epidemic of metabolic disorders remains controversial. Epidemiological studies show growing evidence that consumption of sweetened beverages (containing either sucrose or a mixture of glucose and fructose) is associated with a high energy intake, increased body weight, and the occurrence of metabolic and cardiovascular disorders. There is, however, no unequivocal evidence that fructose intake at moderate doses is directly related with adverse metabolic effects. There has also been much concern that consumption of free fructose, as provided in high fructose corn syrup, may cause more adverse effects than consumption of fructose consumed with sucrose. There is, however, no direct evidence for more serious metabolic consequences of high fructose corn syrup versus sucrose consumption.

Common variation in SIM1 is reproducibly associated with BMI in Pima Indians

OBJECTIVE

Haploinsufficiency of SIM1 is a cause of rare monogenic obesity. To assess the role of SIM1 in polygenic obesity, this gene was analyzed in the Pima Indian population, which has a high prevalence of obesity.

RESEARCH DESIGN AND METHODS

SIM1 was sequenced in 96 individuals. Variants (n = 46) were genotyped in a population-based sample of 3,250 full-heritage Pima Indians and in a separate replication sample of 2,944 predominately non-full-heritage subjects from the same community.

RESULTS

Variants spanning the upstream region of SIM1 through intron 8 were associated with BMI in the full-heritage Pima Indians, where the strongest associations (P approximately 10(-4) to 10(-6)) were with common variants (risk allele frequency 0.61-0.67). The difference in mean BMI between individuals homozygous for the major allele compared with homozygotes for the minor allele was approximately 2.2 kg/m(2) (P = 2 x 10(-5) for rs3213541). These associations replicated in the separate sample of subjects from the same community (P = 5 x 10(-3) for rs3213541). The strongest associations (P = 4 x 10(-7), controlled for age, sex, birth year, and heritage) were seen in the combined sample (n = 6,194). The risk allele for obesity was more common in full-heritage Pimas than in the mixed-heritage subjects. Two variants (rs3734353 and rs3213541) were also genotyped in 1,275 severely obese and 1,395 lean control subjects of French European ancestry. The Pima risk alleles were the minor alleles in the European samples, and these variants did not display any significant association (P > 0.05).

CONCLUSIONS

Common variation in SIM1 is associated with BMI on a population level in Pima Indians where the risk allele is the major allele.

Interaction effects between total energy and macronutrient intakes and angiotensin-converting enzyme 1 (ACE) I/D polymorphism on adiposity-related phenotypes in toddlers and preschoolers: the Growth, Exercise and Nutrition Epidemiological Study in preSchoolers (GENESIS)

The aim of the present study was to investigate the interaction between the angiotensin-converting enzyme 1 (ACE) I/D polymorphism and energy and macronutrient intakes on adiposity-related phenotypes among toddlers and preschoolers. A representative sample of 2374 Greek children aged 1 to 5 years old was examined (Growth, Exercise and Nutrition Epidemiological Study in preSchoolers (GENESIS)). Dietary and anthropometric (i.e. BMI, waist circumference (WC)) assessments were carried out using standard procedures. DNA samples were obtained from 2102 children and were genotyped for theACEI/D polymorphism. Among the entire population, 17 % were ‘at risk of overweight’ and a similar percentage were ‘overweight’. The frequencies of the II, ID and DD genotypes were 16, 46 and 38 %, respectively. Significant interactions were found between theACEI/D polymorphism and total energy intake on WC (P = 0·004 for interaction) and theACEI/D polymorphism and protein intake on BMI and being overweight (P < 0·05 for interaction). Furthermore, it was found that theACEI/D polymorphism may modify the effect of fat intake on WC and BMI, but this interaction disappeared after adjustment for additional potential confounders. Stratified analyses revealed that total energy is correlated with WC and protein intake is associated with BMI and being overweight only among carriers of the D-allele (i.e. DD or ID genotypes). These results suggest that theACEI/D polymorphism may act as a modifying factor in the response of adiposity-related phenotypes to diet.

Adherence rates to the Mediterranean diet are low in a representative sample of Greek children and adolescents

Data from studies in pediatric samples exploring adherence to the Mediterranean diet are scarce. The aim of the present work was to explore adherence to a Mediterranean diet pattern in a representative sample of Greek children and adolescents. The study sample (n = 1305, 3-18 y) was representative of the Greek pediatric population in terms of sex and age. Information on participants' sociodemographic, anthropometric, and lifestyle characteristics were collected through telephone interviews. Adherence to the Mediterranean diet guidelines for adults and to the general dietary guidelines for children was evaluated using KIDMED scores: the higher the score, the more favorable the dietary pattern. The Goldberg cut-off limits for the ratio of energy intake:basal metabolic rate were used to evaluate dietary underreporting and children were accordingly classified as low energy reporters (LER) or non-LER. Only 11.3% of children and 8.3% of adolescents had an optimal KIDMED score (>/=8). In adolescents, partial correlation analysis revealed a negative weak association between KIDMED and BMI (r = -0.092; P = 0.031), which remained significant in the non-LER subgroup (r = -0.137, P = 0.011). Multiple regression analysis revealed that higher KIDMED scores were associated, in non-LER children, with less time spent on sedentary activities (P = 0.002) and higher paternal education (P = 0.050), whereas in adolescents, with younger age (P = 0.001), less time spent on sedentary activities (P = 0.015), higher maternal education (P = 0.014), and higher eating frequency (P = 0.041). In conclusion, low adherence rates to the Mediterranean diet were observed in Greek children and adolescents; this evidence needs to be further explored regarding its impact on health and disease.

Postnatal weight and height growth velocities at different ages between birth and 5 y and body composition in adolescent boys and girls

BACKGROUND

Rapid weight gain in the first years of life is associated with adult obesity. Whether there are critical windows for this long-term effect is unclear.

OBJECTIVE

The objective was to study anthropometric measures in adolescence by sex according to weight and height growth velocities at different ages between birth and 5 y.

DESIGN

Anthropometric measures, including fat and fat-free mass by bipodal impedancemetry, were measured in 468 adolescents aged 8-17 y. We retrospectively collected early infancy data and individually estimated weight and height growth velocities in 69.4% of them using a mathematical model. Associations between birth variables, growth velocities, and anthropometric measures in adolescence were studied.

RESULTS

Weight growth velocity at 3 mo was associated with overweight (odds ratio for a 1-SD increase: 1.52; 95% CI: 1.04, 2.22), fat mass, and waist circumference in adolescence in both sexes and with fat-free mass in boys (r = 0.29, P < 0.001) but not in girls (r = -0.01, NS). Weight growth velocities after 2 y were associated with all anthropometric measures in adolescence, in both sexes. Between 6 mo and 2 y, weight growth velocities were significantly associated only with adolescent height in boys; in girls, associations with fat mass in adolescence were weaker.

CONCLUSION

Our results support the hypothesis of 2 critical windows in early childhood associated with the later risk of obesity: up to 6 mo and from 2 y onward. The study of the determinants of growth during these 2 periods is of major importance for the prevention of obesity in adolescence.

Relationship between gamma-glutamyltransferase and fat mass in a general population of 8–17 years old children. The FLVS II study

AIM

Elevated gamma-glutamyltransferase (GGT) is positively associated with severity of obesity in obese children and with increased BMI and waist circumference in general populations of adults. We aimed to study the relationships between GGT and anthropometric parameters in a general population of children.

METHODS

This cross-sectional study was conducted in 219 boys and 214 girls included in the Fleurbaix Laventie Ville Santé II study. Weight, height, four skinfolds and waist circumference were measured. We compared the means of GGT activity according to gender and Tanner stage, and according to overweight status (IOTF definition) and quartiles of anthropometric parameters. We then calculated partial Pearson correlations by gender between GGT and anthropometric parameters taking age and Tanner stage into account.

RESULTS

GGT activity was higher in boys than in girls as soon as puberty started (P<0.001). The higher difference was observed for Tanner stage III (GGT=10.2 UI/L, CI95% of mean (9.5, 11.1) vs. 7.8 UI/L (7.2, 8.4)). Anthropometric parameters were significantly associated with GGT, particularly waist circumference (r=0.28 in boys; r=0.24 in girls). After an additional adjustment for sum of skinfolds, this correlation disappeared in boys (r=0.06), and was still significant in girls (r=0.19).

CONCLUSION

In a general population of children, overweight and abdominal fat distribution were associated with increased GGT. As some studies have shown that GGT could predict the metabolic syndrome in children and type 2 diabetes in adults, the modest elevation of GGT observed in overweight children may be of pathophysiological importance in the long term.

Genetic study of the melanin-concentrating hormone receptor 2 in childhood and adulthood severe obesity

CONTEXT

The melanin-concentrating hormone receptor 2 (MCHR2) is a G protein-coupled receptor for melanin-concentrating hormone, a neuropeptide that plays an important role in feeding behaviors. MCHR2 maps on chromosome 6q16.3, in a susceptibility locus for childhood obesity.

OBJECTIVE

The aim of this study was to investigate the association between MCHR2 variation and human obesity.

DESIGN

Case control and family-based studies were performed.

PARTICIPANTS

A total of 141 obese children and 24 nonobese adult subjects was sequenced, and case-control analyses were conducted using 628 severely obese children and 1,401 controls.

RESULTS

There were 11 single nucleotide polymorphisms (SNPs) identified. We showed nominal association among -38,245 ATG A/G SNP (P = 0.03; 95% confidence interval 1.02-1.34; odds ratio 1.17), A76A T/C SNP (P = 0.03; 95% confidence interval 0.58-0.97; odds ratio 0.75), and childhood obesity. Analysis of 645 trios with childhood obesity supported further the A76A T/C association, showing an overtransmission to obese children of the at risk T allele (59.0%; P = 0.01), especially in children with most severe forms of obesity (Z score of body mass index > 4) (67.0%; P = 0.003). The A76A at risk T allele was also associated with overeating during meals (P = 0.02) in an additional group of 102 nonobese children. None of the MCHR2 variants, including the A76A SNP, showed association with adult severe obesity, although a trend for association of the T allele of this variant with food disinhibition (P = 0.06) and higher hunger (P = 0.09) was found. This variant was not associated with childhood obesity in an independent case-control study, including 1,573 subjects (P = 0.98). Moreover, the A76A SNP did not explain the linkage on the 6q locus.

CONCLUSION

Our results altogether suggest that MCHR2 is not a major contributor to polygenic obesity and support a modest effect of the A76A SNP on food intake abnormalities in childhood.

Cardiovascular risk factor levels and their relationships with overweight and fat distribution in children: the Fleurbaix Laventie Ville Santé II study

This study aimed to document for the first time in a general population of French children the prevalence and levels of cardiovascular risk factors and to assess separately in boys and girls whether these risk factors were associated with fat mass distribution independently of subcutaneous overall adiposity. A cross-sectional analysis of baseline data from 452 children (235 boys and 217 girls) aged 8 to 17 years included in a 1999 population-based epidemiologic study (the Fleurbaix Laventie Ville Santé II study) was made. Overweight was defined according to the International Obesity Task Force references and the 90th percentiles of the French body mass index curves. The thresholds of parameters defining cardiovascular and metabolic risks were the 95th percentile of the Task Force Report on High Blood Pressure in Children and Adolescents for blood pressure and those of the American Academy of Pediatrics for lipids. Anthropometric and biological parameters were described by sex and according to overweight status. Partial correlations between cardiovascular risk factors and anthropometric measures of adiposity (body mass index, sum of 4 skinfold thicknesses, waist circumference, waist-to-height ratio) were calculated. Then, these correlations were additionally adjusted for the sum of 4 skinfold thicknesses. High plasma triglycerides, high insulin concentration, and low plasma high-density lipoprotein cholesterol (HDL-C) concentration were associated with all measures of adiposity (|r| > or = 0.20, P < .002). When obese children were excluded, overweight children already had high triglycerides and low HDL-C levels, respectively, 2 and 20 times more frequently than normal-weight children did. Among overweight children, 7.7% had at least 2 risk factors among high blood pressure, high plasma triglycerides or glucose, and low HDL-C concentration vs 0.25% among normal-weight children (P = .002). After adjusting for the sum of skinfolds, an independent association between the risk factors and waist circumference was found in girls. In conclusion, (a) modest excess weight is associated with increased levels of cardiovascular risk factors. (b) In girls, abdominal fat distribution is associated with cardiovascular risk factors, independently of overall adiposity. (c) International definition of abdominal obesity in children is required to standardize studies and to progress in the evaluation of childhood obesity and its consequences.

Liquid calories, sugar, and body weight

The consumption of sugar-sweetened beverages has been linked to rising rates of obesity in the United States. The standard explanation is that energy-containing liquids are less satiating than are solid foods. However, purely physiologic mechanisms do not fully account for the proposed links between liquid sugar energy and body weight change. First, a reevaluation of published epidemiologic studies of consumption of sweetened beverages and overweight shows that most such studies either are cross-sectional or are based on passive surveillance of temporal trends and thus permit no conclusions about causal links. Second, research evidence comparing the short-term satiating power of different types of liquids and of solids remains inconclusive. Numerous clinical studies have shown that sugar-containing liquids, when consumed in place of usual meals, can lead to a significant and sustained weight loss. The principal ingredient of liquid meal replacement shakes is sugar, often high-fructose corn syrup, which is present in amounts comparable to those in soft drinks. Far from suppressing satiety, one such liquid shake is marketed on the grounds that it helps control hunger and prevents hunger longer when consumed for the purpose of weight loss. These inconsistencies raise the question whether the issue of sugars and body weight should continue to be framed purely in metabolic or physiologic terms. The effect of sugar consumption on body weight can also depend on behavioral intent, context, and the mode of use, availability, and cost of sweetened liquids.

Are dietary intakes and eating behaviors related to childhood obesity? A comprehensive review of the evidence

The purpose of this article is to comprehensively review studies that have examined the relation between diet and childhood obesity. The review specifically considers the roles of total energy intake and energy density; dietary composition; individual foods, food groups, and dietary patterns; beverage consumption; and eating behaviors. The paper also discusses methodological considerations and future research directions and concludes by summarizing the evidence presented and highlighting the ethical issues surrounding providing dietary advice.

Energy balance and physical activity in obese children attending day-care centres

OBJECTIVE

To evaluate energy balance and physical activity in obese preschool children attending day-care centres.

DESIGN

Cross-sectional study.

SUBJECTS

Twenty-four 3-5 years old obese children selected at random from four different day-care centres in Santiago City, Chile. Total energy expenditure (TEE) was measured by doubly labelled water and physical activity as recorded by TRITRAC R3D motion sensor. Energy intake was assessed by measuring food intake while at the centre, along with the recording of additional food intake in the home.

RESULTS

Obese children had a 5.4% higher weighed energy intake than their energy requirements 2001. Energy intake during the week was 7716+/-1092 kJ/day and 7401+/-1023 kJ/day in boys and girls, respectively. Minimal activity was higher in the day-care centres (62%) compared to 52% during the weekend at home. Light activity was higher during the weekend at home than during the week (25 versus 20%), but moderate-intense activity was similar (3-5%).

CONCLUSIONS

Reduction in dietary energy provided at the day-care centres helps to balance energy requirements during the week. Obese children had marked sedentary characteristics with regards to physical activity, although children are more active at home in weekends. This situation suggests that educators and parents need to improve children's physical activity levels and nutrition habits.

Is dietary intake able to explain differences in body fatness in children and adolescents?

Obesity is the result of an imbalance between energy intake and energy expenditure. Controversial information exists about what are the strongest energy balance aspects influencing body fatness. This article is focused on food consumption facts that could be related to the risk of being obese in children and adolescents. It reviews whether energy intake, macronutrient composition of diet, eating patterns or other dietary intake factors are able to explain differences in body composition when obesity has been already developed or even in subjects at risk to become obese. There is not enough evidence to clarify the importance of diet on overweight children and adolescents, and conclusions derived are somewhat controversial. Cross-sectional and longitudinal studies do not show clear relationships between energy intake or food composition and body fatness. To find relations between dietary factors and childhood obesity perhaps eating patterns or different types of foods must be considered: meal patterns and meal frequency, snacking and beverage consumption, fast food intake, portion sizes, etc. There is no clear association between different aspects of dietary intake and the development of obesity in children and adolescents. Longitudinal and experimental studies are needed in the future.

Anthropometric relationships between parents and children throughout childhood: the Fleurbaix-Laventie Ville Santé Study

BACKGROUND

The study of parent-child anthropometric relationships and their evolution over time may help to better understand familial risk factors for childhood obesity.

METHODS

In a population-based cohort of 124 nuclear families (Fleurbaix-Laventie Ville Santé Study (FLVS) I and II), various anthropometric parameters were measured in both parents and their children, first when the children were prepubescent and again at the end of puberty. Troncular adiposity repartition was estimated by calculating troncular to peripheral skinfolds ratio and waist-to-hip circumferences ratio. Birth and infancy heights and weights were also obtained from the children's health booklets. Parent-child correlations were estimated in infancy, before and at the end of the child's puberty. A prospective analysis was performed to predict the changes in the children's measurements over puberty according to their parents' corresponding baseline values.

RESULTS

BMI and weight correlations at birth were high (>0.30) with the mother and low (<0.10) with the father, then they converged to an intermediate level at 2 y and remained between 0.2 and 0.3 thereafter. Correlations for waist circumference were already present at the prepubertal period and persisted on the same level at the postpubertal period, whereas correlations for subcutaneous adiposity - measured by four skinfolds - and for adiposity distribution - measured by ratios - were higher at the postpubertal period. Moreover, the prospective approach showed that mother's BMI predicted the evolution of her children's BMI over puberty, whereas this relationship was observed more specifically with the father concerning adiposity distribution parameters.

CONCLUSION

Maternal adiposity may act early in life on the adiposity of the child. Maternal and paternal adiposities seem to have quite distinct effects at two key periods of the child's adiposity development such as the prenatal and pubertal periods.

Dietary calcium and body mass index in Portuguese children

OBJECTIVE

The objective of our study was to assess nutritional intake in school children (7-9-y-old) and relate calcium intake to body mass index (BMI).

DESIGN

This study was a cross-sectional analysis.

SETTING

The data were derived from a community-based survey of children from primary schools of Portugal.

SUBJECTS

In all, 3044 Portuguese children (1503 girls and 1541 boys) from a community-based sample of 7-9-y-olds.

METHODS

Height and weight were measured according to international standards, and BMI was calculated. Children's parents completed a self-administered questionnaire that provided information on general family background characteristics and children's physical activity. Children's dietary intake was measured using a 24-h dietary recall. Calcium intake was expressed as the calcium-to-protein ratio, and regression analysis was used to estimate the association between calcium intake and BMI, adjusting for energy intake and confounders.

RESULTS

The prevalence of children with calcium intake below the Dietary Reference Intake was higher in girls (36.4 vs 33.0%, P = 0.053). Calcium-to-protein ratio predicts BMI only in girls (beta = -0.052, P = 0.002), even after adjusting for age, energy intake, parental education, and physical activity.

CONCLUSION

We found an inverse relationship between calcium intake and BMI only in girls. These data reinforce the need for controlled trials to assess the effects of dietary calcium on body mass in each gender.

[Knowledge and gaps on the role of nutrition and physical activity on the onset of childhood obesity]

Childhood and adolescent obesity has increased at alarming rates over the last few years, due to the concurrence of a variety of genetic and environmental factors. The aim of this study was to conduct a review of published studies in the past ten years evaluating the development of childhood obesity in relation to energy and macronutrients intake, their distribution throughout the day and physical activity patterns. 31 articles dealing with this subject were selected. Results obtained appear to indicate that reducing dietary fat and increasing dietary carbohydrate intakes along with consuming an adequate breakfast and carrying out leisure time physical activity on a regular basis act as determining factors to prevent childhood and adolescent obesity, even though the strength of the evidence from these studies is low. It should be a priority to conduct follow-up studies with comparable methodologies in Mediterranean countries, in order to establish parameters for the prevention and control of childhood and adolescent obesity.

Genetics and pathophysiology of human obesity

Obesity has become a leading public health concern. Over 1 billion people are now overweight or obese, and the prevalence of these conditions is rising rapidly. Remarkable new insights into the mechanisms that control body weight are providing an increasingly detailed framework for a better understanding of obesity pathogenesis. Key peripheral signals, such as leptin, insulin, and ghrelin, have been linked to hypothalamic neuropeptide systems, and the anatomic and functional networks that integrate these systems have begun to be elucidated. This article highlights some of these recent findings and their implications for the future of obesity treatment.

Genetics of obesity

Obesity is a typical common multifactorial disease in which environmental and genetic factors interact. In rare cases of severe obesity with childhood onset, a single gene has a major effect in determining the occurrence of obesity, with the environment having only a permissive role in the severity of the phenotype. Exceptional mutations of the leptin gene and its receptor, pro-opiomelanocortine (POMC), prohormone convertase 1 (PC1) and more frequently, mutations in the melanocortin receptor 4 (1 to 4% of very obese cases) have been described. All these obesity genes encode proteins that are strongly connected as part of the same loop of the regulation of food intake. They all involve the leptin axis and one of its hypothalamic targets; the melanocortin pathway. Pathways of bodyweight regulation involved in monogenic forms of obesity might represent targets for future drug development. Successful leptin protein replacement in a leptin-deficient child has contributed to the validation of the usefulness of gene screening in humans. However, the individual variability in response to leptin treatment might be related to genetic variability. The efficiency of leptin itself or of small-molecule agonists of the leptin receptor should be studied in relation with genetic variations in the leptin gene promoter. The most common forms of obesity are polygenic. Two general approaches have been used to date in the search for genes underlying common polygenic obesity in humans. The first approach focuses on selected genes having some plausible role in obesity on the basis of their known or presumed biological role. This approach yielded putative susceptibility genes with only small or uncertain effects. The second approach attempts to map genes purely by position and requires no presumptions on the function of genes. Genome-wide scans identify chromosomal regions showing linkage with obesity in large collections of nuclear families. Genome-wide scans in different ethnic populations have localized major obesity loci on chromosomes 2, 5, 10, 11 and 20. Susceptibility gene(s) for obesity may be positionally cloned in the intervals of linkage. The candidate gene and positional cloning of major obesity-linked regions approaches are discussed in this paper.

Genetics of human obesity

Obesity is a multifactorial condition. Environmental risk factors related to a sedentary life-style and unlimited access to food apply constant pressure in subjects with a genetic predisposition to gain weight. The fact that genetic defects can result in human obesity has been unequivocally established over the past 3 years with the identification of the genetic defects responsible for different monogenic forms of human obesity: the leptin, leptin receptor, pro-opiomelanocortin, pro-hormone convertase-1 and melanocortin-4 receptor genes. The common forms of obesity are, however, polygenic. The examination of specific genes for involvement in the susceptibility to common obesity has not yet yielded convincing results. Approaches involving the candidate genes and the positional cloning of major obesity-linked regions (state-of-the-art future prospects) will be discussed.