Socioeconomic status and weight change in adults: a review

In developed countries, obesity is inversely associated with socioeconomic status (SES) among women, and less consistently among men; whereas, in developing countries, the association is direct. However, the relationship of SES to weight change over time is unknown. This relationship was the focus of the present literature review. It was hypothesized that, compared with persons of higher SES, persons of low SES would show greater weight gain or risk of weight gain over time. A search of electronic databases identified 34 relevant articles from developed countries reporting on studies that assessed the relationship of various measures of SES with weight change over time in adults (there were too few papers from developing countries (n=1) to include). Results of the methodologically strongest studies (those which obtained objectively measured adiposity data and used a follow-up period of 4 years or more) showed that, among non-black samples, there were relatively consistent inverse associations between occupation and weight gain for men and women. When SES was assessed using education, evidence was slightly less consistent, but still provided some support for the hypothesized relationship. However, when income was used as the indicator of SES, findings were inconsistent, although there were fewer studies available. There was little support for a relationship between SES and weight gain for black samples. In the context of the worldwide epidemic of obesity, these findings suggest that in developed countries, weight gain prevention efforts might best be focused on those who are most socioeconomically disadvantaged, particularly those in lower status occupations.

Genetic albation of the c-Cbl ubiquitin ligase domain results in increased energy expenditure and improved insulin action

Casitas b-lineage lymphoma (c-Cbl) is a multiadaptor protein with E3-ubiquitin ligase activity residing within its RING finger domain. We have previously reported that c-Cbl–deficient mice exhibit elevated energy expenditure, reduced adiposity, and improved insulin action. In this study, we examined mice expressing c-Cbl protein with a loss-of-function mutation within the RING finger domain (c-Cbl^A/– mice). Compared with control animals, c-Cbl^A/– mice display a phenotype that includes reduced adiposity, despite greater food intake; reduced circulating insulin, leptin, and triglyceride levels; and improved glucose tolerance. c-Cbl^A/– mice also display elevated oxygen consumption (13%) and are protected against high-fat diet–induced obesity and insulin resistance. Unlike c-Cbl^A/– mice, mice expressing a mutant c-Cbl with the phosphatidylinositol (PI) 3-kinase binding domain ablated (c-Cbl^F/F mice) exhibited an insulin sensitivity, body composition, and energy expenditure similar to that of wild-type animals. These results indicate that c-Cbl ubiquitin ligase activity, but not c-Cbl–dependent activation of PI 3-kinase, plays a key role in the regulation of whole-body energy metabolism.

Change in the prevalence of overweight and obesity among young Australian, 1969-1997

BACKGROUND: Effective public policy requires information on the prevalence of overweight and obesity. OBJECTIVE: We determined changes in the population prevalence of overweight and obesity among young Australians (aged 7-15 y) from 1969 to 1985 to 1997. DESIGN: Data from 5 independent population surveys were analyzed: the Australian Youth Fitness Survey, 1969; the Australian Health and Fitness Survey, 1985; the South Australian Schools Fitness and Physical Activity Survey, 1997; the New South Wales Schools Fitness and Physical Activity Survey, 1997; and the Health of Young Victorians Study, 1997. Measured body mass index was used as the index of adiposity, and recently published body mass index cutoff values were used to categorize each subject as nonoverweight, overweight, obese, or either overweight or obese. RESULTS: For 1985-1997, the population prevalence of overweight increased by 60-70%, obesity increased 2-4-fold, and the combined overweight and obesity categories doubled. The findings were consistent across data sets and between the sexes. For 1969-1985, there was no change in the prevalence of overweight or obesity among girls, but among boys the prevalence of overweight increased by 35%, the prevalence of obesity trebled, and the prevalence of overweight and obesity combined increased by 60%. CONCLUSIONS: The data show that in 1985-1997, the prevalence of overweight and obesity combined doubled and that of obesity trebled among young Australians, but the increase over the previous 16 y was far smaller. These results should increase our sense of urgency in identifying and implementing effective responses to this major threat to public health.

Stability of television viewing and electronic game/computer use in a prospective cohort study of Australian children: relationship with body mass index

Background
While much cross-sectional data is available, there have been few longitudinal investigations of patterns of electronic media use in children. Further, the possibility of a bi-directional relationship between electronic media use and body mass index in children has not been considered. This study aimed to describe longitudinal patterns of television viewing and electronic game/computer use, and investigate relationships with body mass index (BMI).
Methods
This prospective cohort study was conducted in elementary schools in Victoria, Australia. 1278 children aged 5–10 years at baseline and 8–13 years at follow-up had their BMI calculated, from measured height and weight, and transformed to z-scores based on US 2000 growth data. Weight status (non-overweight, overweight and obese) was based on international BMI cut-off points. Weekly television viewing and electronic game/computer use were reported by parents, these were summed to generate total weekly screen time. Children were classified as meeting electronic media use guidelines if their total screen time was ≤14 hrs/wk.
Results
Electronic media use increased over the course of the study; 40% met guidelines at baseline but only 18% three years later. Television viewing and electronic game/computer use tracked moderately and total screen time was positively associated with adiposity cross-sectionally. While weaker relationships with adiposity were observed longitudinally, baseline z-BMI and weight status were positively associated with follow-up screen time and baseline screen time was positively associated with z-BMI and weight status at follow-up. Children who did not meet guidelines at baseline had significantly higher z-BMI and were more likely to be classified as overweight/obese at follow-up.

Conclusion
Electronic media use in Australian elementary school children is high, increases with age and tracks over time. There appears to be a bi-directional association suggesting that interventions targeting reductions in either screen time or adiposity may have a positive effect on both screen time and adiposity.

Association of television viewing with fasting and 2-h postchallenge plasma glucose levels in adults without diagnosed diabetes

OBJECTIVE—We examined the associations of television viewing time with fasting plasma glucose (FPG) and 2-h postchallenge plasma glucose (2-h PG) levels in Australian adults.

RESEARCH DESIGN AND METHODS—A total of 8,357 adults aged >35 years who were free from diagnosed diabetes and who attended a population-based cross-sectional study (Australian Diabetes, Obesity and Lifestyle Study [AusDiab]) were evaluated. Measures of FPG and 2-h PG were obtained from an oral glucose tolerance test. Self-reported television viewing time (in the previous week) was assessed using an interviewer-administered questionnaire. Homeostasis model assessment (HOMA) of insulin sensitivity (HOMA-%S) and ß-cell function (HOMA-%B) were calculated based on fasting glucose and insulin concentrations.

RESULTS—After adjustment for confounders and physical activity time, time spent watching television in women was positively associated with 2-h PG, log fasting insulin, and log HOMA-%B and inversely associated with log HOMA-%S (P < 0.05) but not with FPG. No significant associations were observed with glycemic measures in men. The ß-coefficients across categories of average hours spent watching television per day (<1.0, 1.0–1.9, 2.0–2.9, 3.0–3.9, and ≥4.0) for 2-h PG in women were 0 (reference), 0.009, 0.047, 0.473, and 0.501, respectively (P for trend = 0.02).

CONCLUSIONS—Our findings highlight the unique deleterious relationship of sedentary behavior (indicated by television viewing time) and glycemic measures independent of physical activity time and adiposity status. These relationships differed according to sex and type of glucose measurement, with the 2-h PG measure being more strongly associated with television viewing. The findings suggest an important role for reducing sedentary behavior in the prevention of type 2 diabetes and cardiovascular disease, especially in women.

Angiotensin converting enzyme inhibition from birth reduces body weight and body fat in Sprague-Dawley rats

In vitro studies have demonstrated that angiotensin II (ANG II) induces adipocyte hyperplasia and hypertrophy. The aim of the present study was to determine the effect of angiotensin-converting enzyme inhibition on body weight, adiposity and blood pressure in Sprague–Dawley rats. From birth half of the animals (n = 15) were given water to drink, while the remainder were administered perindopril in their drinking water (2 mg/kg/day). Food intake, water intake and body weight were measured weekly. Blood pressure was measured by tail cuff plethysmography at 11-weeks. Body fat content and distribution were assessed using dual energy X-ray absorptiometry and Magnetic Resonance Imaging at 12 weeks. Animals administered with perindopril had a body fat proportion that was half that of controls. This was consistent with, but disproportionately greater than the observed differences in food intake and body weight. Perindopril treatment completely removed hypertension. We conclude that the chronic inhibition of ANG II synthesis from birth specifically reduces the development of adiposity in the rat.

Overweight, obesity and metabolic syndrome in rural southeastern Australia

OBJECTIVE: To measure the prevalence of overweight, obesity and the metabolic syndrome (MetS) in rural Australia.

DESIGN, SETTING AND PARTICIPANTS: Cross-sectional surveys were conducted in two rural areas in Victoria and South Australia in 2004-2005. A stratified random sample of men and women aged 25-74 years was selected from the electoral roll. Data were collected by a self-administered questionnaire, physical measurements and laboratory tests.

MAIN OUTCOME MEASURES: Prevalence of overweight and obesity, as defined by body mass index (BMI) and waist circumference; prevalence of MetS and its components.

RESULTS: Data on 806 participants (383 men and 423 women) were analysed. Based on BMI, the prevalence of overweight and obesity combined was 74.1% (95% CI, 69.7%-78.5%) in men and 64.1% (95% CI, 59.5%-68.7%) in women. Based on waist circumference, the prevalence of overweight and obesity was higher in women (72.4%; 95% CI, 68.1%-76.7%) than men (61.9%; 95% CI, 57.0%-66.8%). The overall prevalence of obesity was 30.0% (95% CI, 26.8%-33.2%) based on BMI (> or = 30.0 kg/m(2)) and 44.7% (95% CI, 41.2%-48.1%) based on waist circumference (> or = 102 cm [men] and > or= 88 cm [women]). The prevalence of MetS as defined by the US National Cholesterol Education Program Adult Treatment Panel III 2005 criteria was 27.1% (95% CI, 22.7%-31.6%) in men and 28.3% (95% CI, 24.0%-32.6%) in women; based on International Diabetes Federation criteria, prevalences for men and women were 33.7% (95% CI, 29.0%-38.5%) and 30.1% (95% CI, 25.7%-34.5%), respectively. Prevalences of MetS, central (abdominal) obesity, hyperglycaemia, hypertension and hypertriglyceridaemia increased with age.

CONCLUSIONS: In rural Australia, prevalences of MetS, overweight and obesity are very high. Urgent population-wide action is required to tackle the problem.

Stability of body mass index in Australian children: a prospective cohort study across the middle childhood years

Objective: To investigate the prevalence and incidence of overweight and obesity, the frequency of overweight resolution and the influence of parental adiposity during middle childhood.

Design: As part of a prospective cohort study, height and weight were measured in 1997 and 2000/2001. Children were classified as non-overweight, overweight or obese based on standard international definitions. Body mass index (BMI) was transformed into age- and gender-specific Z-scores employing the LMS method and 2000 growth chart data of the Centers for Disease Control and Prevention. Parents self-reported height and weight, and were classified as underweight, healthy weight, overweight or obese based on World Health Organization definitions.

Setting: Primary schools in Victoria, Australia.

Subjects: In total, 1438 children aged 5–10 years at baseline.

Results: The prevalence of overweight and obesity increased between baseline (15.0 and 4.3%, respectively) and follow-up (19.7 and 4.8%, respectively; P < 0.001 for increase in overweight and obesity combined). There were 140 incident cases of overweight (9.7% of the cohort) and 24 of obesity (1.7% of the cohort); only 3.8% of the cohort (19.8% of overweight/obese children) resolved to a healthy weight. The stability of child adiposity as measured by BMI category (84.8% remained in the same category) and BMI Z-score (r = 0.84; mean change = −0.05) was extremely high. Mean change in BMI Z-score decreased with age (linear trend β = 0.03, 95% confidence interval 0.01–0.05). The influence of parental adiposity largely disappeared when children's baseline BMI was adjusted for.

Conclusions: During middle childhood, the incidence of overweight/obesity exceeds the proportion of children resolving to non-overweight. However, for most children adiposity remains stable, and stability appears to increase with age. Prevention strategies targeting children in early childhood are required.

Change in women's body mass index and waist circumference, 1997 to 2002: the Nepean study

Objective: To investigate character istics associated with body mass index (BMI) and waist circumference stability over a five-year period in women with school-age children.

Methods: Women with 7–8 year-old children from western Sydney, Australia, had anthropometric measures taken in 1996/97 (n====436) and five years later (n=327). Socio-demographic characteristics examined at baseline included age, socioeconomic status, smoking, and number of children.

Results: Over five years, less than half of the women maintained a stable BMI (38.8%) or waist circumference (31.5%), with the majority gaining in both indicators of adiposity. BMI and socio-demographic characteristics were not predictive of BMI or waist circumference stability or decrease.

Conclusions and Implications: Total and abdominal adiposity increased in these Australian women who have children. The results support the need to develop effective weight gain prevention initiatives.

The suppressor of cytokine signaling 3 inhibits leptin activation of AMP-Kinase in cultured skeletal muscle of obese humans

Context: Leptin is thought to regulate whole-body adiposity and insulin sensitivity, at least in part, by stimulating fatty acid metabolism via activation of AMP-kinase (AMPK) in skeletal muscle. Human obesity is associated with leptin resistance, and recent studies have demonstrated that hypothalamic expression of the suppressors of cytokine signaling 3 (SOCS3) regulates leptin sensitivity in rodents.

Objective: The objective of the study was to investigate the effects of leptin on fatty acid oxidation and AMPK signaling in primary myotubes derived from lean and obese skeletal muscle and evaluate the contribution of SOCS3 to leptin resistance and AMPK signaling in obese humans.

Results: We demonstrate that leptin stimulates AMPK activity and increases AMPK Thr172 and acetyl-CoA carboxylase-ß Ser222 phosphorylation and fatty acid oxidation in lean myotubes but that in obese subjects leptin-dependent AMPK signaling and fatty acid oxidation are suppressed. Reduced activation of AMPK was associated with elevated expression of IL-6 (~3.5-fold) and SOCS3 mRNA (~2.5-fold) in myotubes of obese subjects. Overexpression of SOCS3 via adenovirus-mediated infection in lean myotubes to a similar degree as observed in obese myotubes prevented leptin but not AICAR (5-amino-imidazole-4-carboxamide-1-ß-D-ribofuranoside) activation of AMPK signaling.

Conclusions: These data demonstrate that SOCS3 inhibits leptin activation of AMPK. These data suggest that this impairment of leptin signaling in skeletal muscle may contribute to the aberrant regulation of fatty acid metabolism observed in obesity and that pharmacological activation of AMPK may be an effective therapy to bypass SOCS3-mediated skeletal muscle leptin resistance for the treatment of obesity-related disorders.

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/m2 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.

Television viewing and abdominal obesity in young adults : is the association mediated by food and beverage consumption during viewing time or reduced leisure-time physical activity?

BACKGROUND:The behavioral pathways through which television (TV) viewing leads to increased adiposity in adults are unclear.

OBJECTIVE:We wanted to determine whether the association between TV viewing and abdominal obesity in young adults is mediated by food and beverage consumption during TV viewing time or by a reduction in overall leisure-time physical activity (LTPA).

DESIGN:This study involved a cross-sectional analysis of data from 2001 Australian adults aged 26–36 y. Waist circumference (WC) was measured at study clinics, and TV viewing time, frequency of food and beverage consumption during TV viewing, LTPA, and demographic characteristics were self-reported.

RESULTS:Women watching TV >3 h/d had a higher prevalence of severe abdominal obesity (WC: =88 cm) compared with women watching =1 h/d [prevalence ratio (PR): 1.89; 95% CI: 1.32, 2.71]. Moderate abdominal obesity (WC: 94–101.9 cm) was more prevalent in men watching TV >3 h/d than in men watching =1 h/d (PR: 2.16; 95% CI: 1.37, 3.41). Adjustment for LTPA made little difference, but adjustment for food and beverage consumption during TV viewing attenuated the associations (PR: 1.48; 95% CI: 1.01, 2.17 for women; PR: 1.73; 95% CI: 1.06, 2.83 for men).

CONCLUSIONS:The association between TV viewing and WC in young adults may be partially explained by food and beverage consumption during TV viewing but was not explained by a reduction in overall LTPA. Other behaviors likely contribute to the association between TV viewing and obesity.

Overweight children have poor bone strength relative to body weight, placing them at greater risk for forearm fractures

Introduction: Obesity is thought to be a protective factor for bones in adults but not in children based on the evidence of the greater incidence of forearm fractures in obese children. Our objective was to investigate the effect of adiposity on bone strength in relation to the mechanical challenge placed onto the forearm bones in case of a fall.

Methods: Cross sectional areas (CSA) were obtained at the mid- and distal radius by peripheral quantitative computed tomography in 486 children (241 boys), mean age 8.3 years (range 6.9–9.7), participating in the LOOK Project. The following parameters were measured: bone mass and bone CSA (both sites), and muscle and fat CSA (mid-forearm only). Bone strength indices combining bone size and total volumetric density were calculated at each site.

Results/Discussion: Overweight children (BMI > percentile equivalent to 25 kg/m² in adults) have higher bone parameters than normal-weight peers (Z-scores +0.6 to +0.9SD, p < 0.0001). These differences disappear after adjustment for muscle CSA. Adiposity (fat CSA/muscle CSA) was negatively correlated with bone mass, size and strength at the distal radius only (r = −0.1, p < 0.05). After adjustment for body weight (estimate of the load during a fall), the negative correlations were stronger and observed at both the mid- and distal radius (r = −0.37 to −0.55, p < 0.0001).

Conclusion. Overweight children have stronger bones due to greater muscle size. However, children with high fat mass relative to muscle mass (increased adiposity) have poorer bone strength, independent of weight, which may contribute to the increased risk of fracture in obese children.

Validity and reliability of measures of television viewing time and other non-occupational sedentary behaviour of adults : a review

Time spent in non-occupational sedentary behaviours (particularly television viewing time) is associated with excess adiposity and an increased risk of metabolic disorders among adults; however, there are no reviews of the validity and reliability of assessing these behaviours. This paper aims to document measures used to assess adults' time spent in leisure-time sedentary behaviours and to review the evidence on their reliability and validity. Medline, CINAHL and Psych INFO databases and reference lists from published papers were searched to identify studies in which leisure-time sedentary behaviours had been measured in adults. Sixty papers reporting measurement of at least one type of leisure-time sedentary behaviour were identified. Television viewing time was the most commonly measured sedentary behaviour. The main method of data collection was by questionnaire. Nine studies examined reliability and three examined validity for the questionnaire method of data collection. Test–retest reliabilities were predominantly moderate to high, but the validity studies reported large differences in correlations of self-completion questionnaire data with the various referent measures used. To strengthen future epidemiological and health behaviour studies, the development of reliable and valid self-report instruments that cover the full range of leisure-time sedentary behaviour is a priority.

Predictors of body mass index change in Australian primary school children

Objective. To assess associations between multiple potential predictors and change in child body mass index (BMI). Methods.In the 1997 Health of Young Victorians Study, children in Grades preparatory to three (aged 510 years) had their height and weight measured. Parents provided information on potential predictors of childhood overweight across six domains (children’s diet, children’s activity level, family composition, sociodemographic factors, prenatal factors and parental adiposity). Measures were repeated three years later in 2000/1. BMI was transformed to standardised (z) scores using the US 2000 Growth Chart data and children were classified as non-overweight or overweight according to international cutpoints.Regression analyses, including baseline BMI z-score as a covariate, assessed the contribution of each potential predictor to change in BMI z-score, development of overweight and spontaneous resolution of overweight in 1 373 children.Results. BMI z-score change was positively associated with frequency of take-away food, food quantity, total weekly screen time, non-Australian paternal country of birth, maternal smoking during pregnancy, and maternal and paternal BMI.Inverse associations were noted for the presence of siblings and rural residence (all pB0.05). Predictors of categorical change (development and resolution of overweight) were less clearly identified, apart from an association between maternal BMI and overweight development (p0.02). Multivariable models suggested individual determinants have a cumulative effect on BMI change. Conclusions. Strong short-term tracking of BMI makes it difficult to identify predictors of change. Nonetheless, putative determinants across all domains assessed were independently associated with adiposity change. Multi-faceted solutions are likely to be required to successfully deal with the complexities of childhood overweight.