Obesity Reviews

Overweight and obesity in youth are important public health concerns and are of particular interest because of possible long‐term associations with adult weight status and morbidity. The aim of this study was to systematically review the literature and update evidence concerning persistence of childhood overweight. A computerized bibliographical search – restricted to studies with a prospective or retrospective longitudinal design – was conducted. Two authors independently extracted data and assessed the methodological quality of the included studies in four dimensions (i) study population and participation rate; (ii) study attrition; (iii) data collection and (iv) data analysis. Conclusions were based on a rating system of three levels of evidence. A total of 25 publications were selected for inclusion in this review. According to a methodological quality assessment, 13 studies were considered to be of high quality. The majority of these high‐quality studies were published after 2001, indicating that recently published data, in particular, provide us with reliable information. All included studies consistently report an increased risk of overweight and obese youth becoming overweight adults, suggesting that the likelihood of persistence of overweight into adulthood is moderate for overweight and obese youth. However, predictive values varied considerably. Limiting aspects with respect to generalizability and methodological issues are discussed.

The relationship between the global food system and the worldwide rapid increase of obesity and related diseases is not yet well understood. A reason is that the full impact of industrialized food processing on dietary patterns, including the environments of eating and drinking, remains overlooked and underestimated. Many forms of food processing are beneficial. But what is identified and defined here as ultra‐processing, a type of process that has become increasingly dominant, at first in high‐income countries, and now in middle‐income countries, creates attractive, hyper‐palatable, cheap, ready‐to‐consume food products that are characteristically energy‐dense, fatty, sugary or salty and generally obesogenic. In this study, the scale of change in purchase and sales of ultra‐processed products is examined and the context and implications are discussed. Data come from 79 high‐ and middle‐income countries, with special attention to Canada and Brazil. Results show that ultra‐processed products dominate the food supplies of high‐income countries, and that their consumption is now rapidly increasing in middle‐income countries. It is proposed here that the main driving force now shaping the global food system is transnational food manufacturing, retailing and fast food service corporations whose businesses are based on very profitable, heavily promoted ultra‐processed products, many in snack form.

Body mass index (BMI) is the cornerstone of the current classification system for obesity and its advantages are widely exploited across disciplines ranging from international surveillance to individual patient assessment. However, like all anthropometric measurements, it is only a surrogate measure of body fatness. Obesity is defined as an excess accumulation of body fat, and it is the amount of this excess fat that correlates with ill‐health. We propose therefore that much greater attention should be paid to the development of databases and standards based on the direct measurement of body fat in populations, rather than on surrogate measures. In support of this argument we illustrate a wide range of conditions in which surrogate anthropometric measures (especially BMI) provide misleading information about body fat content. These include: infancy and childhood; ageing; racial differences; athletes; military and civil forces personnel; weight loss with and without exercise; physical training; and special clinical circumstances. We argue that BMI continues to serve well for many purposes, but that the time is now right to initiate a gradual evolution beyond BMI towards standards based on actual measurements of body fat mass.

This report describes a set of scientific procedures used to assess the impact of foods and food ingredients on the expression of appetite (psychological and behavioural). An overarching priority has been to enable potential evaluators of health claims about foods to identify justified claims and to exclude claims that are not supported by scientific evidence for the effect cited. This priority follows precisely from the principles set down in the PASSCLAIM report. The report allows the evaluation of the strength of health claims, about the effects of foods on appetite, which can be sustained on the basis of the commonly used scientific designs and experimental procedures. The report includes different designs for assessing effects on satiation as opposed to satiety, detailed coverage of the extent to which a change in hunger can stand alone as a measure of appetite control and an extensive discussion of the statistical procedures appropriate for handling data in this field of research. Because research in this area is continually evolving, new improved methodologies may emerge over time and will need to be incorporated into the framework. One main objective of the report has been to produce guidance on good practice in carrying out appetite research, and not to set down a series of commandments that must be followed.

Maternal obesity is linked with adverse outcomes for mothers and babies. To get an overview of risks related to obesity in pregnant women, a systematic review of reviews was conducted. For inclusion, reviews had to compare pregnant women of healthy weight with women with obesity, and measure a health outcome for mother and/or baby. Authors conducted full‐text screening, quality assurance using the AMSTAR tool and data extraction steps in pairs. Narrative analysis of the 22 reviews included show gestational diabetes, pre‐eclampsia, gestational hypertension, depression, instrumental and caesarean birth, and surgical site infection to be more likely to occur in pregnant women with obesity compared with women with a healthy weight. Maternal obesity is also linked to greater risk of preterm birth, large‐for‐gestational‐age babies, foetal defects, congenital anomalies and perinatal death. Furthermore, breastfeeding initiation rates are lower and there is greater risk of early breastfeeding cessation in women with obesity compared with healthy weight women. These adverse outcomes may result in longer duration of hospital stay, with concomitant resource implications. It is crucial to reduce the burden of adverse maternal and foetal/child outcomes caused by maternal obesity. Women with obesity need support to lose weight before they conceive, and to minimize their weight gain in pregnancy.

The relationship between body mass index (BMI) (in midlife and late‐life) and dementia was investigated in meta‐analyses of 16 articles reporting on 15 prospective studies. Follow‐ups ranged from 3.2 to 36.0 years. Meta‐analyses were conducted on samples including 25 624 participants evaluated for Alzheimer's disease (AD), 15 435 participants evaluated for vascular dementia (VaD) and 30 470 followed for any type of dementia (Any Dementia). Low BMI in midlife was associated with 1.96 [95% confidence interval (CI): 1.32, 2.92] times the risk of developing AD. The pooled relative risks for AD, VaD and Any Dementia for overweight BMI in midlife compared with normal BMI were 1.35 (95% CI:1.19, 1.54), 1.33 (95% CI: 1.02, 1.75) and 1.26 (95% CI: 1.10, 1.44), respectively. The pooled relative risks of AD and Any Dementia for obese BMI in midlife compared to normal BMI were 2.04 (95% CI: 1.59, 2.62) and 1.64 (95% CI: 1.34, 2.00), respectively. Continuous BMI in late‐life was not associated with dementia. Small numbers of studies included in pooled analyses reduce generalizability of findings, and emphasize the need for publication of additional findings. We conclude that underweight, overweight and obesity in midlife increase dementia risk. Further research evaluating late‐life BMI and dementia is required.

Drug addiction and obesity appear to share several properties. Both can be defined as disorders in which the saliency of a specific type of reward (food or drug) becomes exaggerated relative to, and at the expense of others rewards. Both drugs and food have powerful reinforcing effects, which are in part mediated by abrupt dopamine increases in the brain reward centres. The abrupt dopamine increases, in vulnerable individuals, can override the brain's homeostatic control mechanisms. These parallels have generated interest in understanding the shared vulnerabilities between addiction and obesity. Predictably, they also engendered a heated debate. Specifically, brain imaging studies are beginning to uncover common features between these two conditions and delineate some of the overlapping brain circuits whose dysfunctions may underlie the observed deficits. The combined results suggest that both obese and drug‐addicted individuals suffer from impairments in dopaminergic pathways that regulate neuronal systems associated not only with reward sensitivity and incentive motivation, but also with conditioning, self‐control, stress reactivity and interoceptive awareness. In parallel, studies are also delineating differences between them that centre on the key role that peripheral signals involved with homeostatic control exert on food intake. Here, we focus on the shared neurobiological substrates of obesity and addiction.

The objective of this study was to evaluate the evidence on whether childhood obesity is a risk factor for adult disease, independent of adult body mass index (BMI). Ovid MEDLINE (1948–May 2011), EMBASE (1980–2011 week 18) and the Cochrane Library (1990–2011) were searched for published studies of BMI from directly measured weight and height in childhood (2–19 years) and disease outcomes in adulthood. Data were synthesized in a narrative fashion. Thirty‐nine studies (n 181–1.1 million) were included in the review. There was evidence for associations between childhood BMI and type 2 diabetes, hypertension and coronary heart disease. Few studies examined associations independent of adult BMI; these showed that effect sizes were attenuated after adjustment for adult BMI in standard regression analyses. Although there is a consistent body of evidence for associations between childhood BMI and cardiovascular outcomes, there is a lack of evidence for effects independent of adult BMI. Studies have attempted to examine independent effects using standard adjustment for adult BMI, which is subject to over‐adjustment and problems with interpretation. Studies that use more robust designs and analytical techniques are needed to establish whether childhood obesity is an independent risk factor for adult disease.

During the last decades, eating out of home (OH) has gained importance in the diets worldwide. We document the nutritional characteristics of eating OH and its associations with energy intake, dietary quality and socioeconomic status. We carried out a systematic review of peer‐reviewed studies in eight databases up to 10 March 2011. Of the 7,319 studies retrieved, 29 met the inclusion criteria and were analysed in this review. The quality of the data was assessed and a sensitivity analysis was conducted by isolating nationally representative or large cohort data from 6 and 11 countries, respectively. OH foods were important sources of energy in all age groups and their energy contribution increased in adolescents and young adults. Eating OH was associated with a higher total energy intake, energy contribution from fat in the daily diet and higher socioeconomic status. Two large studies showed how eating OH was also associated with a lower intake of micronutrients, particularly vitamin C, Ca and Fe. Although the studies were cross‐sectional and heterogeneous in the way they classified eating OH, we conclude that eating OH is a risk factor for higher energy and fat intake and lower micronutrient intake.