Louise A. Baur

Skeletal Muscle Triglyceride Levels Are Inversely Related to Insulin Action

In animal studies, increased amounts of triglyceride associated with skeletal muscle (mTG) correlate with reduced skeletal muscle and whole body insulin action. The aim of this study was to test this relationship in humans. Subjects were 38 nondiabetic male Pima Indians (mean age 28 ± 1 years). Insulin sensitivity at physiological (M) and supraphysiological (MZ) insulin levels was assessed by the euglycemic clamp. Lipid and carbohydrate oxidation were determined by indirect calorimetry before and during insulin administration. mTG was determined in vastus lateralis muscles obtained by percutaneous biopsy. Percentage of body fat (mean 29 ± 1%, range 14–44%) was measured by underwater weighing. In simple regressions, negative relationships were found between mTG (mean 5.4 ± 0.3 μmol/g, range 1.3–1.9 μmol/g) and log10M (r = −0.53, P ≤ 0.001), MZ (r = −0.44, P = 0.006), and nonoxidative glucose disposal (r = −0.48 and −0.47 at physiological and supraphysiological insulin levels, respectively, both P = 0.005) but not glucose or lipid oxidation. mTG was not related to any measure of adiposity. In multiple regressions, measures of insulin resistance (log10M, MZ, log10[fasting insulin]) were significantly related to mTG independent of all measures of obesity (percentage of body fat, BMI, waist-to-thigh ratio). In turn, all measures of obesity were related to the insulin resistance measures independent of mTG. The obesity measures and mTG accounted for similar proportions of the variance in insulin resistance in these relationships. The results suggest that in this human population, as in animal models, skeletal muscle insulin sensitivity is strongly influenced by local supplies of triglycerides, as well as by remote depots and circulating lipids. The mechanism(s) underlying the relationship between mTG and insulin action on skeletal muscle glycogen synthesis may be central to an understanding of insulin resistance.

Dietary fats and insulin action

The history of research into the relationship between dietary fat intake and impaired insulin action has its origin in the work of Himsworth approximately 60 years ago [1, 2]. In a series of pioneering studies using crude indices of insulin action and limited subject numbers (only one in an often quoted paper!), Himsworth linked high levels of fat intake with insulin resistance, and conversely, improved insulin action with predominantly carbohydrate diet. However, the link was tenuous and really apparent only at the extreme ends of the dietary spectrum (<20 or > 80 % of calories as fat). These studies, flawed as they were, influenced the field enormously in the absence of any significant work in the area for a remarkable period of time. The conclusions reached by Himsworth were reinforced to some extent by misuse of glucose tolerance data that showed deteriorations following periods on diets extremely low in carbohydrate (< 50 g/day) and improvement on liquid formula diets providing a remarkably high percentage (75-85 %) of calories from carbohydrate [3-5]. It was really not until the 1980 s that the development of acceptable techniques for the measurement of insulin action in vivo allowed the relationship between dietary fat intake and insulin action to be accurately assessed. These studies have essentially been confined to investigations in rodents and humans.

Effectiveness of Lifestyle Interventions in Child Obesity: Systematic Review With Meta-analysis

BACKGROUND AND OBJECTIVES: The effects of lifestyle interventions on cardio-metabolic outcomes in overweight children have not been reviewed systematically. The objective of the study was to examine the impact of lifestyle interventions incorporating a dietary component on both weight change and cardio-metabolic risks in overweight/obese children. METHODS: English-language articles from 1975 to 2010, available from 7 databases, were used as data sources. Two independent reviewers assessed articles against the following eligibility criteria: randomized controlled trial, participants overweight/obese and ≤18 years, comparing lifestyle interventions to no treatment/wait-list control, usual care, or written education materials. Study quality was critically appraised by 2 reviewers using established criteria; Review Manager 5.1 was used for meta-analyses. RESULTS: Of 38 eligible studies, 33 had complete data for meta-analysis on weight change; 15 reported serum lipids, fasting insulin, or blood pressure. Lifestyle interventions produced significant weight loss compared with no-treatment control conditions: BMI (−1.25kg/m2, 95% confidence interval [CI] −2.18 to −0.32) and BMI z score (−0.10, 95% CI −0.18 to −0.02). Studies comparing lifestyle interventions to usual care also resulted in significant immediate (−1.30kg/m2, 95% CI −1.58 to −1.03) and posttreatment effects (−0.92 kg/m2, 95% CI −1.31 to −0.54) on BMI up to 1 year from baseline. Lifestyle interventions led to significant improvements in low-density lipoprotein cholesterol (−0.30 mmol/L, 95% CI −0.45 to −0.15), triglycerides (−0.15 mmol/L, 95% CI −0.24 to −0.07), fasting insulin (−55.1 pmol/L, 95% CI −71.2 to −39.1) and blood pressure up to 1 year from baseline. No differences were found for high-density lipoprotein cholesterol. CONCLUSIONS: Lifestyle interventions can lead to improvements in weight and cardio-metabolic outcomes. Further research is needed to determine the optimal length, intensity, and long-term effectiveness of lifestyle interventions.

A prospective examination of children's time spent outdoors, objectively measured physical activity and overweight

Objective: This study aimed to determine whether time spent outdoors was associated with objectively measured physical activity, body mass index (BMI) z-score and overweight in elementary-school aged children, cross-sectionally and prospectively over 3 years.Methods: Three-year cohort study with data collected during 2001 and 2004. Nineteen randomly selected state elementary schools across Melbourne, Australia. One hundred and eighty eight 5–6-year-old and 360 10–12-year-old children. Baseline parent reports of childrens time spent outdoors during warmer and cooler months, on weekdays and weekends. At baseline and follow-up, childrens moderate and vigorous physical activity (MVPA) was objectively assessed by accelerometry, and BMI z-score and overweight was calculated from measured height and weight.Results: Cross-sectionally, each additional hour outdoors on weekdays and weekend days during the cooler months was associated with an extra 27 min week−1 MVPA among older girls, and with an extra 20 min week−1 MVPA among older boys. Longitudinally, more time outdoors on weekends predicted higher MVPA on weekends among older girls and boys (5 min week−1). The prevalence of overweight among older children at follow-up was 27–41% lower among those spending more time outdoors at baseline.Conclusion: Encouraging 10–12-year-old children to spend more time outdoors may be an effective strategy for increasing physical activity and preventing increases in overweight and obesity. Intervention research investigating the effect of increasing time outdoors on childrens physical activity and overweight is warranted.

A century of trends in adult human height

Being taller is associated with enhanced longevity, and higher education and earnings. We reanalysed 1472 population-based studies, with measurement of height on more than 18.6 million participants to estimate mean height for people born between 1896 and 1996 in 200 countries. The largest gain in adult height over the past century has occurred in South Korean women and Iranian men, who became 20.2 cm (95% credible interval 17.5–22.7) and 16.5 cm (13.3–19.7) taller, respectively. In contrast, there was little change in adult height in some sub-Saharan African countries and in South Asia over the century of analysis. The tallest people over these 100 years are men born in the Netherlands in the last quarter of 20th century, whose average heights surpassed 182.5 cm, and the shortest were women born in Guatemala in 1896 (140.3 cm; 135.8–144.8). The height differential between the tallest and shortest populations was 19-20 cm a century ago, and has remained the same for women and increased for men a century later despite substantial changes in the ranking of countries. DOI: http://dx.doi.org/10.7554/eLife.13410.001

Twelve-Month Effectiveness of a Parent-led, Family-Focused Weight-Management Program for Prepubertal Children: A Randomized, Controlled Trial

BACKGROUND. Parenting-skills training may be an effective age-appropriate child behavior-modification strategy to assist parents in addressing childhood overweight. OBJECTIVE. Our goal was to evaluate the relative effectiveness of parenting-skills training as a key strategy for the treatment of overweight children. DESIGN. The design consisted of an assessor-blinded, randomized, controlled trial involving 111 (64% female) overweight, prepubertal children 6 to 9 years of age randomly assigned to parenting-skills training plus intensive lifestyle education, parenting-skills training alone, or a 12-month wait-listed control. Height, BMI, and waist-circumference z score and metabolic profile were assessed at baseline, 6 months, and 12 months (intention to treat). RESULTS. After 12 months, the BMI z score was reduced by ∼10% with parenting-skills training plus intensive lifestyle education versus ∼5% with parenting-skills training alone or wait-listing for intervention. Waist-circumference z score fell over 12 months in both intervention groups but not in the control group. There was a significant gender effect, with greater reduction in BMI and waist-circumference z scores in boys compared with girls. CONCLUSION. Parenting-skills training combined with promoting a healthy family lifestyle may be an effective approach to weight management in prepubertal children, particularly boys. Future studies should be powered to allow gender subanalysis.

Outcomes and costs of primary care surveillance and intervention for overweight or obese children: the LEAP 2 randomised controlled trial

Objective To determine whether ascertainment of childhood obesity by surveillance followed by structured secondary prevention in primary care improved outcomes in overweight or mildly obese children. Design Randomised controlled trial nested within a baseline cross sectional survey of body mass index (BMI). Randomisation and outcomes measurement, but not participants, were blinded to group assignment. Setting 45 family practices (66 general practitioners) in Melbourne, Australia. Participants 3958 children visiting their general practitioner in May 2005-July 2006 were surveyed for BMI. Of these, 258 children aged 5 years 0 months up to their 10th birthday who were overweight or obese by International Obesity Taskforce criteria were randomised to intervention (n=139) or control (n=119) groups. Children who were very obese (UK BMI z score ≥3.0) were excluded. Intervention Four standard consultations over 12 weeks targeting change in nutrition, physical activity, and sedentary behaviour, supported by purpose designed family materials. Main outcomes measures Primary measure was BMI at 6 and 12 months after randomisation. Secondary measures were mean activity count/min by 7-day accelerometry, nutrition score from 4-day abbreviated food frequency diary, and child health related quality of life. Differences were adjusted for socioeconomic status, age, sex, and baseline BMI. Results Of 781 eligible children, 258 (33%) entered the trial; attrition was 3.1% at 6 months and 6.2% at 12 months. Adjusted mean differences (intervention − control) at 6 and 12 months were, for BMI, −0.12 (95% CI −0.40 to 0.15, P=0.4) and −0.11 (−0.45 to 0.22, P=0.5); for physical activity in counts/min, 24 (−4 to 52, P=0.09) and 11 (−26 to 49, P=0.6); and, for nutrition score, 0.2 (−0.03 to 0.4, P=0.1) and 0.1 (−0.1 to 0.4, P=0.2). There was no evidence of harm to the child. Costs to the healthcare system were significantly higher in the intervention arm. Conclusions Primary care screening followed by brief counselling did not improve BMI, physical activity, or nutrition in overweight or mildly obese 5-10 year olds, and it would be very costly if universally implemented. These findings are at odds with national policies in countries including the US, UK, and Australia. Trial registration ISRCTN 52511065 (www.isrctn.org)

A synthesis of existing systematic reviews and meta-analyses of school-based behavioural interventions for controlling and preventing obesity

Schools are an attractive and popular setting for implementing interventions for children. There is a growing body of empirical research exploring the efficacy of school‐based obesity prevention programs. While there have been several reviews on the topic, findings remain mixed. To examine the quality of evidence and compare the findings from existing systematic reviews and meta‐analyses of school‐based programs in the prevention and control of childhood obesity. This paper systematically appraises the methodology and conclusions of literature reviews examining the effectiveness of school‐based obesity interventions published in English in peer‐reviewed journals between January 1990 and October 2010. Eight reviews were examined, three meta‐analyses and five systematic reviews. All of the reviews recognized that studies were heterogeneous in design, participants, intervention and outcomes. Intervention components in the school setting associated with a significant reduction of weight in children included long‐term interventions with combined diet and physical activity and a family component. Several reviews also found gender differences in response to interventions. Of the eight reviews, five were deemed of high quality and yet limited evidence was found on which to base recommendations. As no single intervention will fit all schools and populations, further high‐quality research needs to focus on identifying specific program characteristics predictive of success.

Does obesity influence foot structure and plantar pressure patterns in prepubescent children

OBJECTIVE: This study examined the effects of obesity on plantar pressure distributions in prepubescent children.DESIGN: Field-based, experimental data on BMI (body mass index), foot structure and plantar pressures were collected for 13 consenting obese children and 13 non-obese controls.SUBJECTS: Thirteen obese (age 8.1±1.2 y; BMI 25.5±2.9 kg/m2) and 13 non-obese (age 8.4±0.9 y; BMI 16.9±1.2 kg/m2) prepubescent children, matched to the obese children for gender, age and height.MEASUREMENTS: Height and weight were measured to calculate BMI. Static weight-bearing footprints for the right and left foot of each subject were recorded using a pedograph to calculate the footprint angle and the Chippaux–Smirak index as representative measures of the surface area of the foot in contact with the ground. Right and left foot plantar pressures were then obtained using a mini-emed® pressure platform to calculate the force and pressure experienced under each childs foot during static and dynamic loaded and unloaded conditions.RESULTS: Obese subjects displayed significantly lower footprint angle (t=4.107; P=<0.001) values and higher Chippaux–Smirak index values (t=−6.176; P=<0.001) compared to their non-obese counterparts. These structural foot changes were associated with differences in plantar pressures between the two subject groups. That is, although rearfoot dynamic forces generated by the obese subjects were significantly higher than those generated by the non-obese subjects, these forces were experienced over significantly higher mean peak areas of contact with the mini-emed® system. Therefore, rearfoot pressures experienced by the two subject groups did not differ. However, the mean peak dynamic forefoot pressures generated by the obese subjects (39.3±15.7 N·cm−2; q=3.969) were significantly higher than those generated by the non-obese subjects (32.3±9.2 N·cm−2).CONCLUSIONS: It is postulated that foot discomfort-associated structural changes and increased forefoot plantar pressures in the obese foot may hinder obese children from participating in physical activity and therefore warrants immediate further investigation.

Effectiveness of home based early intervention on children’s BMI at age 2: randomised controlled trial

Objective To assess the effectiveness of a home based early intervention on children’s body mass index (BMI) at age 2. Design Randomised controlled trial. Setting The Healthy Beginnings Trial was conducted in socially and economically disadvantaged areas of Sydney, Australia, during 2007-10. Participants 667 first time mothers and their infants. Intervention Eight home visits from specially trained community nurses delivering a staged home based intervention, one in the antenatal period, and seven at 1, 3, 5, 9, 12, 18 and 24 months after birth. Timing of the visits was designed to coincide with early childhood developmental milestones. Main outcome measures The primary outcome was children’s BMI (the healthy BMI ranges for children aged 2 are 14.12-18.41 for boys and 13.90-18.02 for girls). Secondary outcomes included infant feeding practices and TV viewing time when children were aged 2, according to a modified research protocol. The data collectors and data entry staff were blinded to treatment allocation, but the participating mothers were not blinded. Results 497 mothers and their children (75%) completed the trial. An intention to treat analysis in all 667 participants recruited, and multiple imputation of BMI for the 170 lost to follow-up and the 14 missing, showed that mean BMI was significantly lower in the intervention group (16.53) than in the control group (16.82), with a difference of 0.29 (95% confidence interval −0.55 to −0.02; P=0.04). Conclusions The home based early intervention delivered by trained community nurses was effective in reducing mean BMI for children at age 2. Trial registration Australian Clinical Trial Registry No 12607000168459.