Obesity Reviews

Shrewsbury, V. A.; Steinbeck, K. S.; Torvaldsen, S.; Baur, L. A.

doi: 10.1111/j.1467-789X.2011.00882.xpmid: 21535361

The study aims to describe clinical recommendations (i) on the role of parents in both pre‐adolescent and adolescent overweight and obesity treatment; (ii) to health professionals on how to involve parents in paediatric overweight and obesity treatment and (iii) to identify deficiencies in the associated literature. A systematic literature review was conducted in March 2010 to identify clinical practice guidelines, position or consensus statements on clinical management of paediatric overweight or obesity, developed by a national or international health professional association or government agency, and endorsed for current use. Relevant clinical recommendations in these documents were identified via a screen for the words ‘parent’, ‘family’ and synonyms. Twenty documents were included. Most documents emphasized the importance of involving parents or the family in paediatric overweight and obesity treatment with approximately a third of documents providing separate recommendations on the role of parents/family for pre‐adolescents and adolescents. The documents varied markedly with regard to the presence of recommendations on parent/family involvement in the various components of lifestyle interventions or bariatric surgery. Almost half of the documents contained recommendations to health professionals regarding interactions with parents. High‐quality research is needed on age‐specific techniques to optimize the involvement of parents and family members in paediatric overweight and obesity treatment.

Cheng, H‐R.; Walker, L. O.; Tseng, Y‐F.; Lin, P‐C.

doi: 10.1111/j.1467-789X.2011.00886.xpmid: 21545682

Obesity is a health issue for people in Asia, and many studies support that childbearing may contribute to women's obesity. However, most studies of post‐partum weight retention (PWR) focus on Western countries. This paper aimed to review recent data on PWR and discuss the related factors of PWR for women in Asia. Three electronic databases – MEDLINE, CINAHL and PsycINFO – were searched for data from January 1990 to August 2010. Twelve studies were identified as containing information related to PWR. Chinese, Taiwanese and Korean women tend to have higher gestational weight gain and PWR than women in other Asian countries in this review. The average reported gestational weight gain in these studies ranged from 8.3 kg to 18.0 kg, and the average weight retention at 6 months post partum in various countries ranged from 1.56 kg to 4.1 kg. Gestational weight gain had a positive effect on PWR, but there were no consistent conclusions for other factors. Only a few psychosocial and behavioural factors have been studied. Moreover, no one has assessed changes in waist circumference and waist‐to‐hip ratio for measuring central obesity and ensuring risk of chronic disease. Focusing on changes in maternal weight and body composition, and considering the impact of psychological and behavioural factors are suggested for future studies in Asia.

Lubans, D. R.; Hesketh, K.; Cliff, D. P.; Barnett, L. M.; Salmon, J.; Dollman, J.; Morgan, P. J.; Hills, A. P.; Hardy, L. L.

doi: 10.1111/j.1467-789X.2011.00896.xpmid: 21676153

The aim of this review was to evaluate the reliability and validity of methods used to assess the multiple components of sedentary behaviour (i.e. screen time, sitting, not moving and existing at low energy expenditure) in children and adolescents. Twenty‐six studies met our inclusion criteria and were reviewed. Thirteen studies reported the reliability of self‐ and proxy‐report measures of sedentary behaviour and seven of these were found to have acceptable test–retest reliability. Evidence for the criterion validity of self‐ and proxy‐report measures was examined in three studies with mixed results. Seven studies examined the reliability and/or validity of direct observation and the findings were generally positive. Five studies demonstrated the utility of accelerometers to accurately classify sedentary behaviour. Self‐report measures provide reliable estimates of screen time, yet their validity remains largely untested. While accelerometers can accurately classify participants' behaviour as sedentary, they do not provide information about type of sedentary behaviour or context. Studies utilizing measures of sedentary behaviour need to more adequately report on the validity and reliability of the measures used. We recommend the use of objective measures of sedentary behaviour such as accelerometers, in conjunction with subjective measures (e.g. self‐report), to assess type and context of behaviour.

Joseph, R. J.; Alonso‐Alonso, M.; Bond, D. S.; Pascual‐Leone, A.; Blackburn, G. L.

doi: 10.1111/j.1467-789X.2011.00893.xpmid: 21676151

As obesity rates increase worldwide, healthcare providers require methods to instill the lifestyle behaviours necessary for sustainable weight loss. Designing effective weight‐loss interventions requires an understanding of how these behaviours are elicited, how they relate to each other and whether they are supported by common neurocognitive mechanisms. This may provide valuable insights to optimize existing interventions and develop novel approaches to weight control. Researchers have begun to investigate the neurocognitive underpinnings of eating behaviour and the impact of physical activity on cognition and the brain. This review attempts to bring these somewhat disparate, yet interrelated lines of literature together in order to examine a hypothesis that eating behaviour and physical activity share a common neurocognitive link. The link pertains to executive functions, which rely on brain circuits located in the prefrontal cortex. These advanced cognitive processes are of limited capacity and undergo relentless strain in the current obesogenic environment. The increased demand on these neurocognitive resources as well as their overuse and/or impairment may facilitate impulses to over‐eat, contributing to weight gain and obesity. This impulsive eating drive may be counteracted by physical activity due to its enhancement of neurocognitive resources for executive functions and goal‐oriented behaviour. By enhancing the resources that facilitate ‘top‐down’ inhibitory control, increased physical activity may help compensate and suppress the hedonic drive to over‐eat. Understanding how physical activity and eating behaviours interact on a neurocognitive level may help to maintain a healthy lifestyle in an obesogenic environment.

Paschetta, E.; Hvalryg, M.; Musso, G.

doi: 10.1111/j.1467-789X.2011.00897.xpmid: 21815989

Glucose‐dependent insulinotropic polypeptide (GIP) is a hormone secreted from the intestinal K‐cells with established insulin‐releasing actions. However, the GIP receptor is widely distributed in peripheral organs, including the adipose tissue, gut, bone and brain, where GIP modulates energy intake, cell metabolism and proliferation, and lipid and glucose metabolism, eventually promoting lipid and glucose storage. In diabetes and obesity, the incretin effect of GIP is blunted, while the extrapancreatic tissues keep a normal sensitivity to this hormone. As GIP levels are normal or elevated in obesity and diabetes, mounting evidence from chemical or genetic GIP deletion in animal models of obesity‐related diabetes suggests that GIP may have a pro‐obesogenic action and that a strategy antagonizing GIP action may be beneficial in these conditions, clearing triglyceride deposits from adipose tissue, liver and muscle, and restoring normal insulin sensitivity. Emerging evidence also suggests that the metabolic benefits of bypass surgery are mediated, at least in part, by surgical removal of GIP‐secreting K‐cells in the upper small intestine.

van de Woestijne, A. P.; Monajemi, H.; Kalkhoven, E.; Visseren, F. L. J.

doi: 10.1111/j.1467-789X.2011.00900.xpmid: 21749607

Elevated plasma triglyceride levels, as often seen in obese subjects, are independently associated with an increased risk of cardiovascular diseases. By secreting adipokines (such as adiponectin and leptin) and other proteins (such as lipoprotein lipase and cholesteryl ester transferase protein), adipose tissue affects triglyceride metabolism. In obesity, adipocyte hypertrophy leads to many changes in adipocyte function and production of anti‐ and pro‐inflammatory cytokines. Furthermore, free fatty acids are released into the circulation contributing to insulin resistance. Adipose tissue dysfunction will eventually lead to abnormalities in lipid metabolism, such as hypertriglyceridemia (due to increased hepatic very‐low‐density lipoprotein production and decreased triglyceride hydrolysis), small dense low‐density lipoprotein particles, remnant lipoproteins and low high‐density lipoprotein cholesterol levels, all associated with a higher risk for the development of cardiovascular diseases. The clinical implications of elevated plasma triglycerides are still a matter of debate. Understanding the pathophysiology of adipose tissue dysfunction in obesity, which is becoming a pandemic condition, is essential for designing appropriate therapeutic interventions. Lifestyle changes are important to improve adipose tissue function in obese patients. Pharmacological interventions to improve adipose tissue function need further evaluation. Although statins are not very potent in reducing plasma triglycerides, they remain the mainstay of therapy for cardiovascular risk reduction in high‐risk patients.

Jeukendrup, A. E.; Randell, R.

doi: 10.1111/j.1467-789X.2011.00908.xpmid: 21951331

The term ‘fat burner’ is used to describe nutrition supplements that are claimed to acutely increase fat metabolism or energy expenditure, impair fat absorption, increase weight loss, increase fat oxidation during exercise, or somehow cause long‐term adaptations that promote fat metabolism. Often, these supplements contain a number of ingredients, each with its own proposed mechanism of action and it is often claimed that the combination of these substances will have additive effects. The list of supplements that are claimed to increase or improve fat metabolism is long; the most popular supplements include caffeine, carnitine, green tea, conjugated linoleic acid, forskolin, chromium, kelp and fucoxanthin. In this review the evidence for some of these supplements is briefly summarized. Based on the available literature, caffeine and green tea have data to back up its fat metabolism‐enhancing properties. For many other supplements, although some show some promise, evidence is lacking. The list of supplements is industry‐driven and is likely to grow at a rate that is not matched by a similar increase in scientific underpinning.

Kiens, B.; Alsted, T. J.; Jeppesen, J.

doi: 10.1111/j.1467-789X.2011.00898.xpmid: 21951332

In modern societies, oversupply of calories leads to obesity and chronic metabolic stress, which may lead to development of disease. Oversupply of calories is often associated with elevated plasma lipid concentrations and accumulation of lipids in skeletal muscle leading to decreased insulin sensitivity. Consequently, enhanced fat oxidation might be beneficial in counteracting lipid accumulation. Exercise is the most effective way to increase fat oxidation, because it increases metabolic rate. Lipid metabolism can also be altered by dietary manipulations. Thus, a fat rich diet leads to increased potential for fat oxidation by increasing the content of several of the proteins in the fat oxidative pathway. The regulation of both exercise and diet induced lipid oxidation will be discussed in this review.

Astrup, A.

doi: 10.1111/j.1467-789X.2011.00894.xpmid: 21692967

Cells, tissues and organisms have the ability to rapidly switch substrate oxidation from carbohydrate to fat in response to changes in nutrient intake, and to changes in energy demands, environmental cues and internal signals. In healthy, metabolically normal individuals, substrate switching occurs rapidly and completely; in other words, substrate switching is ‘flexible’. A growing body of evidence demonstrates that a blunted substrate switching from low‐ to high‐fat oxidation exists in obese individuals, as well as in pre‐obese and post‐obese, and that this ‘metabolic inflexibility’ may be a genetically determined trait. A decreased fat oxidation can lead to a positive energy balance under conditions of high‐fat feeding, due to depletion of glycogen stores that stimulates appetite and energy intake through glucostatic and glucogenostatic mechanisms, e.g. hepatic sensing of glycogen stores. Several genetic polymorphisms and single‐nucleotide polymorphisms have been identified that are associated with low‐fat oxidation rates and metabolic inflexibility, and genetic identification of susceptible individuals may lead to personalized prevention of weight gain using fat oxidation stimulants (‘fat burners’) in the future.

Dulloo, A. G.

doi: 10.1111/j.1467-789X.2011.00909.xpmid: 21951333

The concept of managing obesity through the stimulation of thermogenesis is currently a focus of considerable attention by the pharmaceutical, nutraceutical and functional food industries. This paper first reviews the landmark discoveries that have fuelled the search for thermogenic anti‐obesity products that range from single‐target drugs to multi‐target functional foods. It subsequently analyses the thermogenic and fat‐oxidizing potentials of a wide array of bioactive food ingredients which are categorized under methylxanthines, polyphenols, capsaicinoids/capsinoids, minerals, proteins/amino acids, carbohydrates/sugars and fats/fatty acids. The main outcome of this analysis is that the compounds or combination of compounds with thermogenic and fat‐oxidizing potentials are those that possess both sympathomimetic stimulatory activity and acetyl‐coA carboxylase inhibitory property, and are capable of targeting both skeletal muscle and brown adipose tissue. The thermogenic potentials of products so far tested in humans range from marginal to modest, i.e. 2–5% above daily energy expenditure. With an increasing number of bioactive food ingredients awaiting screening in humans, there is hope that this thermogenic potential could be safely increased to 10–15% above daily energy expenditure – which would have clinically significant impact on weight management, particularly in the prevention of obesity and in improving the long‐term prognosis of post‐slimming weight maintenance.