Effect of childhood obesity prevention programmes on blood lipids: a systematic review and meta‐analysis

We aimed to assess the effects of childhood obesity prevention programmes on blood lipids in high‐income countries. We searched MEDLINE®, Embase, PsychInfo, CINAHL®, clinicaltrials.gov , and the Cochrane Library up to 22 April 2013 for relevant randomized controlled trials, quasi‐experimental studies and natural experiments published in English. Studies were included if they implemented diet and/or physical activity intervention(s) with ≥1 year follow‐up (or ≥6 months for school‐based intervention studies) in 2–18‐year‐olds, and were excluded if they targeted only overweight/obese children, or those with a pre‐existing medical condition. Seventeen studies were finally included. For total cholesterol, the pooled intervention effect was ?0.97 mg dL^?1 [95% confidence interval (CI): ?3.26, 1.32; P = 0.408]; for low‐density lipoprotein cholesterol (LDL‐C), ?6.06 mg dL^?1 (95% CI: ?11.09, ?1.02; P = 0.018); for high‐density lipoprotein cholesterol (HDL‐C), 1.87 mg dL^?1 (95% CI: 0.39, 3.34; P = 0.013); and for triglycerides, ?1.95 mg dL^?1 (95% CI: ?4.94, 1.04; P = 0.202). Most interventions (70%) showed similar significant or no effects on adiposity‐ and lipids outcomes: 15% interventions improved both adiposity‐ and lipids outcomes; 55% had no significant effects on either. Childhood obesity prevention programmes had a significant desirable effect on LDL‐C and HDL‐C. Two‐thirds of interventions showed similar significant or no effects in adiposity‐ and lipids outcomes. Assessing lipids outcomes provide additional useful information on obesity prevention programme benefits.     

Maternal body mass index and post‐term birth: a systematic review and meta‐analysis

Post‐term birth is a preventable cause of perinatal mortality and severe morbidity. This review examined the association between maternal body mass index (BMI) and post‐term birth at ≥42 and ≥41 weeks' gestation. Five databases, reference lists and citations were searched from May to November 2015. Observational studies published in English since 1990 were included. Linear and nonlinear dose–response meta‐analyses were conducted by using random effects models. Sensitivity analyses assessed robustness of the results. Meta‐regression and sub‐group meta‐analyses explored heterogeneity. Obesity classes were defined as I (30.0–34.9 kg m^?2), II (35.0–39.9 kg m^?2) and III (≥40 kg m^?2; IIIa 40.0–44.9 kg m^?2, IIIb ≥ 45.0 kg m^?2). Searches identified 16,375 results, and 39 studies met the inclusion criteria (n = 4,143,700 births). A nonlinear association between maternal BMI and births ≥42 weeks was identified; odds ratios and 95% confidence intervals for obesity classes I–IIIb were 1.42 (1.27–1.58), 1.55 (1.37–1.75), 1.65 (1.44–1.87) and 1.75 (1.50–2.04) respectively. BMI was linearly associated with births ≥41 weeks: odds ratio is 1.13 (95% confidence interval 1.05–1.21) for each 5‐unit increase in BMI. The strength of the association between BMI and post‐term birth increases with increasing BMI. Odds are greatest for births ≥42 weeks among class III obesity. Targeted interventions to prevent the adverse outcomes associated with post‐term birth should consider the difference in risk between obesity classes.     

Maternal pre‐pregnancy obesity and child neurodevelopmental outcomes: a meta‐analysis

This review examined evidence of the association between maternal pre‐pregnancy overweight/obesity status and child neurodevelopmental outcomes. PubMed and PsycINFO databases were systematically searched for empirical studies published before April 2017 using keywords related to prenatal obesity and children's neurodevelopment. Of 1483 identified papers, 41 were included in the systematic review, and 32 articles representing 36 cohorts were included in the meta‐analysis. Findings indicated that compared with children of normal weight mothers, children whose mothers were overweight or obese prior to pregnancy were at increased risk for compromised neurodevelopmental outcomes (overweight: OR = 1.17, 95% CI [1.11, 1.24], I² = 65.51; obese: OR = 1.51; 95% CI [1.35, 1.69], I² = 79.63). Pre‐pregnancy obesity increased the risk of attention deficit–hyperactivity disorder (OR = 1.62; 95% CI [1.23, 2.14], I² = 70.15), autism spectrum disorder (OR = 1.36; 95% CI [1.08, 1.70], I² = 60.52), developmental delay (OR = 1.58; 95% CI [1.39, 1.79], I² = 75.77) and emotional/behavioural problems (OR = 1.42; 95% CI [1.26, 1.59], I² = 87.74). Given the current obesity prevalence among young adults and women of childbearing age, this association between maternal obesity during pregnancy and atypical child neurodevelopment represents a potentially high public health burden.     

The role of maternal obesity in infant outcomes in polycystic ovary syndrome—A systematic review,meta‐analysis,and meta‐regression

Polycystic ovary syndrome (PCOS) is associated with worsened pregnancy and infant outcomes, higher body mass index (BMI), and longitudinal weight gain. Despite most of the clinical features of PCOS being risk factors for worsened infant outcomes in the general population, their impact on infant outcomes in PCOS is unknown. We aimed to investigate the association of PCOS with infant outcomes considering maternal adiposity, other known risk factors, and potential confounders. The meta‐analyses included 42 studies in 7041 women with PCOS and 63 722 women without PCOS. PCOS was associated with higher gestational weight gain (GWG) and with higher preterm birth and large for gestational age and with lower birth weight with this association varying by geographic continent, PCOS phenotypes, and study quality. However, PCOS was associated with none of these outcomes on BMI‐matched studies. Gestational diabetes was significantly associated with an increased preterm birth on meta‐regression. We report for the first time that GWG is higher in PCOS. Infant outcomes vary by geographic continent and study quality but are similar in BMI‐matched women with and without PCOS. This suggests that infant outcomes in PCOS may be related to maternal obesity. These novel findings warrant future studies in PCOS investigating screening and management of infant outcomes with consideration of maternal obesity.     

Transgenerational effects of caloric restriction on appetite: a meta‐analysis

Maternal undernutrition can result in significant alterations to the post‐natal offspring phenotype, including body size and behaviour. For example, maternal food restriction has been implicated in offspring hyperphagia, potentially causing increased weight gain and fat accumulation. This could result in obesity and other adverse long‐term health effects in offspring. We investigated the link between maternal caloric restriction during gestation and offspring appetite by conducting the first meta‐analysis on this topic using experimental data from mammalian laboratory models (i.e. rats and mice). We collected 89 effect sizes from 35 studies, together with relevant moderators. Our analysis revealed weak and statistically non‐significant overall effect on offspring's appetite. However, we found that lower protein content of restricted diets is associated with higher food intake in female offspring. Importantly, we show that a main source of variation among studies arises from whether, and how, food intake was adjusted for body mass. This probably explains many of the contradictory results in the field. Based on our results, we recommend using allometric scaling of food intake to body mass in future studies.     

Adiposity and risk of thyroid cancer: a systematic review and meta‐analysis

Thyroid cancer incidence has increased rapidly over time, as has obesity prevalence. A link between the two appears plausible, but the relation of adiposity to thyroid cancer remains incompletely understood. We performed a meta‐analysis of adiposity measures and thyroid cancer using studies identified through October 2014. Twenty‐one articles yielded data on 12,199 thyroid cancer cases. We found a statistically significant 25% greater risk of thyroid cancer in overweight individuals and a 55% greater thyroid cancer risk in obese individuals as compared with their normal‐weight peers. Each 5‐unit increase in body mass index (BMI), 5 kg increase in weight, 5 cm increase in waist or hip circumference and 0.1‐unit increase in waist‐to‐hip ratio were associated with 30%, 5%, 5% and 14% greater risks of thyroid cancer, respectively. When evaluated by histologic type, obesity was significantly positively related to papillary, follicular and anaplastic thyroid cancers, whereas it revealed an inverse association with medullary thyroid cancer. Both general and abdominal adiposity are positively associated with thyroid cancer. However, relations with BMI vary importantly by tumour histologic type.     

Effect of behavioural techniques and delivery mode on effectiveness of weight management: systematic review,meta‐analysis and meta‐regression

A systematic review, meta‐analysis and meta‐regression were conducted to evaluate the effectiveness of behavioural weight management programmes and examine how programme characteristics affect mean weight loss. Randomized controlled trials of multicomponent behavioural weight management programmes in overweight and obese adults were included. References were obtained through systematic searches of electronic databases (conducted November 2012), screening reference lists and contacting experts. Two reviewers extracted data and evaluated risk of bias. Thirty‐seven studies, representing over 16,000 participants, were included. The pooled mean difference in weight loss at 12 months was ?2.8 kg (95% confidence interval [CI] ?3.6 to ?2.1, P < 0.001). I² indicated that 93% of the variability in outcome was due to differences in programme effectiveness. Meta‐analysis showed no evidence that supervised physical activity sessions (mean difference 1.1 kg, 95% CI ?2.65 to 4.79, P = 0.08), more frequent contact (mean difference ?0.3 kg, 95% CI ?0.7 to 0.2, P = 0.25) or in‐person contact (mean difference 0.0 kg, 95% CI ?1.8 to 1.8, P = 0.06) were related to programme effectiveness at 12 months. In meta‐regression, calorie counting (?3.3 kg, 95% CI ?4.6 to ?2.0, P = 0.027), contact with a dietitian (?1.5 kg, 95% CI ?2.9 to ?0.2, P < 0.001) and use of behaviour change techniques that compare participants' behaviour with others (?1.5 kg, 95% CI ?2.9 to ?0.1, P = 0.032) were associated with greater weight loss. There was no evidence that other programme characteristics were associated with programme effectiveness. Most but not all behavioural weight management programmes are effective. Programmes that support participants to count calories or include a dietitian may be more effective, but the programme characteristics explaining success are mainly unknown.     

Increased maternal pregnancy complications in polycystic ovary syndrome appear to be independent of obesity—A systematic review,meta‐analysis,and meta‐regression

Polycystic ovary syndrome (PCOS) is associated with an increased risk of maternal pregnancy and delivery complications. However, the impact of clinical features of PCOS and other potential risk factors in PCOS is still unknown. We aimed to investigate the association of PCOS with maternal pregnancy and delivery complications with consideration of risk factors and potential confounders. The meta‐analysis included 63 studies. PCOS was associated with higher miscarriage, gestational diabetes mellitus, gestational hypertension, pre‐eclampsia, induction of labour, and caesarean section. The association of PCOS with these outcomes varied by geographic continent, PCOS phenotypes, and study quality. Pre‐eclampsia and induction of labour were not associated with PCOS on body mass index‐matched studies. No outcome was associated with PCOS on assisted pregnancies. Age was significantly associated with higher miscarriage on meta‐regression. There were no studies assessing perinatal depression. We confirm that PCOS is associated with an increased risk of maternal pregnancy and delivery complications. The association of PCOS with the outcomes is worsened in hyperandrogenic PCOS phenotypes, in specific geographic continents, and in the highest quality studies but disappears in assisted pregnancies. Future studies in PCOS are warranted to investigate proper timing for screening and prevention of maternal pregnancy and delivery complications with consideration of clinical features of PCOS.     

The impact of maternal BMI status on pregnancy outcomes with immediate short‐term obstetric resource implications: a meta‐analysis

Obesity is rising in the obstetric population, yet there is an absence of services and guidance for the management of maternal obesity. This systematic review aimed to investigate relationships between obesity and impact on obstetric care. Literature was systematically searched for cohort studies of pregnant women with anthropometric measurements recorded within 16‐weeks gestation, followed up for the term of the pregnancy, with at least one obese and one comparison group. Two researchers independently data‐extracted and quality‐assessed each included study. Outcome measures were those that directly or indirectly impacted on maternity resources. Primary outcomes included instrumental delivery, caesarean delivery, duration of hospital stay, neonatal intensive care, neonatal trauma, haemorrhage, infection and 3rd/4th degree tears. Meta‐analysis shows a significant relationship between obesity and increased odds of caesarean and instrumental deliveries, haemorrhage, infection, longer duration of hospital stay and increased neonatal intensive care requirement. Maternal obesity significantly contributes to a poorer prognosis for mother and baby during delivery and in the immediate post‐partum period. National clinical guidelines for management of obese pregnant women, and public health interventions to help safeguard the health of mothers and their babies are urgently required.     

The effects of morbid obesity on maternal and neonatal health outcomes: a systematic review and meta‐analyses

Morbidly obese (Class III, body mass index [BMI] ≥ 40 kg m^?2) women constitute 8% of reproductive‐aged women and are an increasing proportion; however, their pregnancy risks have not yet been well understood. Hence, we performed meta‐analyses following the MOOSE (Meta‐Analysis of Observational Studies in Epidemiology) guideline, searching Medline and Embase from their inceptions. To examine graded relationships, we compared Class III obesity to Class I and I/II, and separately to normal weight. We found important effects on all three primary outcomes in morbidly obese women: preterm birth <37 weeks was 31% higher compared with Class I (relative risk [RR] 1.31 [1.19, 1.43]) and 20% higher than Class I/II (RR 1.20 [1.13, 1.27]), large‐for‐gestational age was higher (RR 1.37 [1.29, 1.45] and RR 1.30 [1.24, 1.36] compared with Class I and I/II, respectively), while small‐for‐gestational age was lower (RR 0.89 [0.84, 0.93] compared with Class I, with nearly identical reductions for Class I/II). Morbidly obese women have higher risks of preterm birth, large‐for‐gestational age and numerous other adverse maternal and infant health outcomes, relative to not only normal weight but also Class I or I/II obese women. These findings have important implications for screening and care of morbidly obese pregnant women, to try to decrease adverse outcomes.     

The influence of maternal body mass index,maternal diabetes mellitus,and maternal smoking during pregnancy on the risk of childhood‐onset type 1 diabetes mellitus in the offspring: Systematic review and meta‐analysis of observational studies

There is emerging evidence that events occurring before and shortly after birth may be important in determining the risk of childhood‐onset type 1 diabetes mellitus (T1DM). We aimed to summarize and synthesize the associations between maternal body mass index (BMI), maternal diabetes mellitus (DM), and maternal smoking during pregnancy and the risk of childhood‐onset T1DM in the offspring by performing a systematic review and meta‐analysis of observational studies. A random effects model was used to generate the summary risk estimates. The PubMed and Web of Science databases were searched to identify relevant observational studies. Twenty one observational studies were included in the present meta‐analysis. Compared with offspring of mothers with normal weight, offspring of women with overweight or obesity were at an increased risk of developing childhood‐onset T1DM (overweight: relative risk [RR] 1.09, 95% confidence interval [CI], 1.03‐1.15; obesity: RR 1.25, 95% CI, 1.16‐1.34; per 5 kg m^?2 increase in BMI: RR 1.10, 95% CI, 1.06‐1.13). No association was found for maternal underweight (RR 0.92, 95% CI, 0.75‐1.13). Maternal DM was associated with an increased risk of childhood‐onset T1DM (RR 3.26, 95% CI, 2.84‐3.74). Regarding the type of maternal DM, the greatest risk of T1DM in the offspring appeared to be conferred by maternal T1DM (RR 4.46, 95% CI, 2.89‐6.89), followed by maternal gestational diabetes mellitus (RR 1.66, 95% CI, 1.16‐2.36), and lastly by maternal type 2 diabetes mellitus (RR 1.11, 95% CI, 0.69‐1.80). Additional analysis of studies comparing maternal versus paternal T1DM within the same population revealed that offspring of fathers with T1DM had a 1.5 times higher risk of developing childhood‐onset T1DM than offspring of mothers with T1DM (RR 9.58, 95% CI, 6.33‐14.48 vs. RR 6.24, 95% CI, 5.52‐7.07). Furthermore, a reduced risk of childhood‐onset T1DM was observed in infants born to mothers who smoked during pregnancy compared with infants born to mothers who did not smoke during pregnancy (RR 0.79, 95% CI, 0.71‐0.87). In summary, our findings add further evidence that early‐life events or environmental factors may play a role in modulating infants' risk of developing T1DM later in life.     

Gestational weight gain in relation to offspring obesity over the life course: a systematic review and bias‐adjusted meta‐analysis

Gestational weight gain (GWG) is considered one of the risk factors for future obesity in the offspring. However, the direction and strength of this association at different periods of offspring life is relatively unknown. This study investigates whether excess or inadequate maternal GWG during pregnancy influences the risk of offspring obesity at different stages in life. A systematic review of published articles was undertaken after a comprehensive search of different databases, and extracted data were meta‐analysed. To quantify offspring obesity estimates in relation to GWG, we stratified obesity estimates within three life stages of the offspring age: <5 years, 5 to <18 years and 18+ years. Our meta‐analysis showed that, compared with offspring of women with adequate GWG, offspring of women who gained inadequate gestational weight were at a decreased risk of obesity (relative risk [RR]: 0.86; 95% confidence interval [CI]: 0.78–0.94), and offspring of women who gained excess weight were at an increased risk of obesity (RR: 1.40; 95% CI: 1.23–1.59). These relationships were similar after stratification by life stage. Findings of this study therefore suggest that excess GWG does influence offspring obesity over the short‐ and long‐term, and should therefore be avoided.     

A systematic review and meta‐analysis on the effects of exercise training versus hypocaloric diet: distinct effects on body weight and visceral adipose tissue

Exercise training (‘exercise’) and hypocaloric diet (‘diet’) are frequently prescribed for weight loss in obesity. Whilst body weight changes are commonly used to evaluate lifestyle interventions, visceral adiposity (VAT) is a more relevant and stronger predictor for morbidity and mortality. A meta‐analysis was performed to assess the effects of exercise or diet on VAT (quantified by radiographic imaging). Relevant databases were searched through May 2014. One hundred seventeen studies (n = 4,815) were included. We found that both exercise and diet cause VAT loss (P < 0.0001). When comparing diet versus training, diet caused a larger weight loss (P = 0.04). In contrast, a trend was observed towards a larger VAT decrease in exercise (P = 0.08). Changes in weight and VAT showed a strong correlation after diet (R² = 0.737, P < 0.001), and a modest correlation after exercise (R² = 0.451, P < 0.001). In the absence of weight loss, exercise is related to 6.1% decrease in VAT, whilst diet showed virtually no change (1.1%). In conclusion, both exercise and diet reduce VAT. Despite a larger effect of diet on total body weight loss, exercise tends to have superior effects in reducing VAT. Finally, total body weight loss does not necessarily reflect changes in VAT and may represent a poor marker when evaluating benefits of lifestyle‐interventions.     

Obesity and iron deficiency: a quantitative meta‐analysis

Hypoferraemia (i.e. iron deficiency) was initially reported among obese individuals several decades ago; however, whether obesity and iron deficiency are correlated remains unclear. Here, we evaluated the putative association between obesity and iron deficiency by assessing the concentration of haematological iron markers and the risks associated with iron deficiency in both obese (including overweight) subjects and non‐overweight participants. We performed a systematic search in the databases PubMed and Embase for relevant research articles published through December 2014. A total of 26 cross‐sectional and case–control studies were analysed, comprising 13,393 overweight/obese individuals and 26,621 non‐overweight participants. Weighted or standardized mean differences of blood iron markers and odds ratio (OR) of iron deficiency were compared between the overweight/obese participants and the non‐overweight participants using a random‐effects model. Compared with the non‐overweight participants, the overweight/obese participants had lower serum iron concentrations (weighted mean difference [WMD]: ?8.37 μg dL^?1; 95% confidence interval [CI]: ?11.38 to ?5.36 μg dL^?1) and lower transferrin saturation percentages (WMD: 2.34%, 95% CI: ?3.29% to ?1.40%). Consistent with this finding, the overweight/obese participants had a significantly increased risk of iron deficiency (OR: 1.31; 95% CI: 1.01–1.68). Moreover, subgroup analyses revealed that the method used to diagnose iron deficiency can have a critical effect on the results of the association test; specifically, we found a significant correlation between iron deficiency and obesity in studies without a ferritin‐based diagnosis, but not in studies that used a ferritin‐based diagnosis. Based upon these findings, we concluded that obesity is significantly associated with iron deficiency, and we recommend early monitoring and treatment of iron deficiency in overweight and obese individuals. Future longitudinal studies will help to test whether causal relationship exists between obesity and iron deficiency.     

Targeting bile acid metabolism in obesity reduction: A systematic review and meta‐analysis

A systematic review and meta‐analysis was conducted of studies that address the association of bile acid (BA) with obesity and of studies on the effects of treatment in patients with obesity on BA metabolism, assessed from systemic BA, fibroblast growth factor 19 (FGF19), 7α‐hydroxy‐4‐cholesten‐3‐one (C4) level, and faecal BA. We searched PubMed, Embase, and the Cochrane Library from inception to 1 August 2019 using the keywords obesity, obese, body mass index, and overweight with bile acid, FGF19, FXR, and TGR5. Two reviewers independently searched, selected, and assessed the quality of studies. Data were analysed using either fixed or random effect models with inverse variance weighting. Of 3771 articles, 33 papers were relevant for the association of BA with obesity of which 22 were included in the meta‐analysis, and 50 papers were relevant for the effect of obesity interventions on BA of which 20 were included in the meta‐analysis. Circulating fasting total BA was not associated with obesity. FGF19 was inversely and faecal BA excretion was positively associated with obesity. Roux‐en‐Y gastric bypass (RYGB) and sleeve gastrectomy (SG) modulated BA metabolism, ie, increased BA and FGF19. Our results indicate that BA metabolism is altered in obesity. Certain bariatric surgeries including RYGB and SG modulate BA, whether these underlie the beneficial effect of the treatment should be investigated.     

Comparison of a high saturated fat diet with a high carbohydrate diet during pregnancy and lactation: effects on insulin sensitivity in offspring of rats

Insulin resistance plays a critical role in metabolic syndrome and is influenced by the amount and saturation of dietary fat. Both prenatal over and under nutrition can program susceptibility to insulin resistance. The aim of the study was to explore the impact of dietary fat given to mothers during gestation on the insulin sensitivity of the offspring. Female Wistar rats were fed with diets rich in carbohydrate (CHO) or saturated fat (SAFA) during pregnancy. The male offspring was split into 5 subgroups: groups 1 (control) and 3 continued on CHO or SAFA after birth, respectively. Group 2 with mothers on CHO continued on the CHO diet during the nursing period and changed to SAFA postweaning. Group 4 with mothers on SAFA continued on SAFA during the weaning period and changed to CHO postweaning. For group 5 the offspring of mothers given SAFA diet was changed to nursing mothers on CHO diet immediately after birth and continued on the same diet postweaning. At the age of 16 weeks, a euglycemic hyperinsulinemic clamp was performed. The glucose infusion rate was lowered in the groups receiving the SAFA diet (group 2, 24.7 +/- 2.0 mg/kg per minute; group 3, 22.0 +/- 1.9 mg/kg per minute; P < .05) compared with group 1 (32.2 +/- 2.3 mg/kg per minute). We did not detect any alterations in the rate of glucose disappearance during the clamp for any of the groups compared with group 1. A diet high in SAFA given to mothers during gestation and/or the weaning period does not seem to have deleterious effects on the insulin sensitivity in the offspring.     

Association between maternal body mass index and congenital heart defects in infants: A meta‐analysis

We conducted this meta‐analysis to address the open question of a possible association between maternal body mass index (BMI) and congenital heart defects (CHDs) in infants. We conducted a comprehensive computerized search of PubMed, Web of Science, Medline, and Embase databased (January 1980 through August 2017). We assessed the association between maternal BMI and the risk for congenital heart defects in their offspring. Study‐specific relative risk estimates were polled according to random‐effect or fixed‐effect models. From 2567 citations, a total of 13 case‐control studies and 4 cohort studies were selected for a meta‐analysis, including more than 1 150 000 cases. The pooled odds radio (OR) of 1.065 (95% confidence interval [CI], 1.021‐1.100; P = .001; I²= 60.1%) indicated a positive effect of maternal overweight status (BMI 25.0–29.9 kg/m²) on the risk for congenital heart defects in infants. Moreover, we observed a significant association between maternal obesity (BMI ≥ 30 kg/m²) and congenital heart defects in their offspring (OR: 1.174; 95% CI, 1.146–1.203, P = 0.161; I² =25.5%). However, there was little significant evidence of an association between maternal underweight status (BMI < 18.5 kg/m²) and offspring with congenital heart defects, and the pooled OR was 1.015 (95% CI, 0.980–1.052; P = 0.085; I²=34.0%). Our meta‐analysis provides robust evidence of the positive association between maternal BMI and the risk for fetal congenital heart defects.