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Review article: biological mechanisms for symptom causation by individual FODMAP subgroups - the case for a more personalised approach to dietary restriction.
Wang, XJ, Camilleri, M, Vanner, S, Tuck, C
Alimentary pharmacology & therapeutics. 2019;(5):517-529
Abstract
BACKGROUND Due to the paucity of targeted therapy for irritable bowel syndrome (IBS), many patients turn to dietary modifications for symptom management. The combination of five subgroups of poorly absorbed and rapidly fermented carbohydrates-fructans, galacto-oligosaccharides, lactose, excess fructose and polyols-are thought to trigger gastrointestinal symptoms and are referred to collectively as "FODMAPs". AIMS To examine the biological plausibility and mechanisms by which foods high in specific FODMAP subgroups cause symptoms, and to use this information to explore the possibility of targeting select dietary components to allow for a more personalised approach to dietary adjustment METHODS Recent literature was analysed via search databases including Medline, PubMed and Scopus. RESULTS Lactose, fructans and galacto-oligosaccharides have strong biologic plausibility for symptom generation due to lack of hydrolases resulting in distention from osmosis and rapid fermentation. However, excess fructose and polyols may only cause symptoms in specific individuals when consumed in high doses, but this remains to be established. There is evidence to suggest that certain patient characteristics such as ethnicity may predict response to lactose, but differentiation of other subgroups is difficult prior to dietary manipulation. CONCLUSIONS While some clear mechanisms of action for symptom generation have been established, further research is needed to understand which patients will respond to specific FODMAP subgroup restriction. We suggest that clinicians consider in some patients a tailored, personalised "bottom-up" approach to the low-FODMAP diet, such as dietary restriction relevant to the patients' ethnicity, symptom profile and usual dietary intake.
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Pros & cons of some popular extreme weight-loss diets.
Joshi, S, Mohan, V
The Indian journal of medical research. 2018;(5):642-647
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Abstract
Obesity has now become a huge public health issue not only in the developed world but also in developing countries. In view of the health hazards associated with obesity and more importantly for cosmetic reasons, many people, particularly the youth, have started resorting to 'extreme' weight-loss diets to achieve a rapid reduction in weight. These extreme diets are either very low in carbohydrate or very low in fat. Such extreme diets not only make the diet unbalanced but also have safety issues. Moreover, these are not sustainable in the long run. The weight that is lost is regained within a short period of time when people go off these extreme diets. This explains why the popularity of most extreme diets peaks as well as wanes rapidly. Instead of resorting to such extreme diets, correction of obesity is best achieved with balanced, healthy, nutritious diets which are low in calories, combined with adequate physical activity (exercise). Motivational counselling can also help people to initiate weight loss and sustain this weight loss over longer periods of time.
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Gene-Diet Interaction and Precision Nutrition in Obesity.
Heianza, Y, Qi, L
International journal of molecular sciences. 2017;(4)
Abstract
The rapid rise of obesity during the past decades has coincided with a profound shift of our living environment, including unhealthy dietary patterns, a sedentary lifestyle, and physical inactivity. Genetic predisposition to obesity may have interacted with such an obesogenic environment in determining the obesity epidemic. Growing studies have found that changes in adiposity and metabolic response to low-calorie weight loss diets might be modified by genetic variants related to obesity, metabolic status and preference to nutrients. This review summarized data from recent studies of gene-diet interactions, and discussed integration of research of metabolomics and gut microbiome, as well as potential application of the findings in precision nutrition.
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A Systematic Review of Evidence on the Use of Very Low Calorie Diets in People with Diabetes.
Sellahewa, L, Khan, C, Lakkunarajah, S, Idris, I
Current diabetes reviews. 2017;(1):35-46
Abstract
BACKGROUND Recent interest has emerged regarding the effects of Very Low Calorie Diet (VLCD) in people with type 2 diabetes (T2D). We therefore performed a systematic review to investigate the effects of VLCD on HbA1c, weight and cardiovascular risk profile outcomes as well as its safety and tolerability among people with T2D. METHODS We conducted searches of Cochrane Database of Systematic Reviews, Centre for reviews and Dissemination databases, Medline, Embase, Pubmed, Web of Science, Web of Knowledge and Turning Research into Practice (TRIP) as well as ongoing trial resources. We included all studies involving VLCD and diabetes published until December 2013. Outcome measures include weight, HbA1c, fasting glucose, fasting insulin, lipid profile, blood pressure, safety and drop out rates. RESULTS 17 studies were included in the systematic review. Duration of VLCD duration ranged from 5 days to 6 months and duration of follow up ranged from 8 days to 5 years. The age range was 14 years to 59 years of age. Mean weight loss was 13.2kg, ranging from 4.1 to 24kg. Mean Hba1c reduction was 1.4% (ranging between 0.1 to 3.1% reduction across different studies). Three studies reported a significant reduction in the daily doses of insulin. All studies which reported cardiovascular risk profile showed a significant decrease in total cholesterol, systolic and diastolic blood pressure post VLCD. Apart from two studies, all of the other studies showed that the decrease in blood pressure and total cholesterol was not only present immediately post VLCD, but it was also maintained at follow up. However it is important to note that the follow up periods did differ between studies. Overall, drop out rates ranged from 4.7% to 33% and appeared to be lower during the active intervention phase compared with during the follow-up period. No major adverse event was reported apart from one study which recorded a non-fatal myocardial infarction. CONCLUSION This review demonstrated that VLCD in people with T2D was associated with significant weight loss, reduction in blood glucose profile and improvement in cardiovascular risk profile, high tolerability and good safety outcomes. Studies were heterogeneous and longer term outcomes data post VLCD is still required.
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Extended calorie restriction suppresses overall and specific food cravings: a systematic review and a meta-analysis.
Kahathuduwa, CN, Binks, M, Martin, CK, Dawson, JA
Obesity reviews : an official journal of the International Association for the Study of Obesity. 2017;(10):1122-1135
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Abstract
BACKGROUND Multiple studies have concluded that calorie restriction for at least 12 weeks is associated with reduced food cravings, while others have shown that calorie restriction may increase food cravings. We addressed this ambiguity in a systematic review and meta-analysis. METHODS We searched for studies conducted on subjects with obesity, implemented calorie restriction for at least 12 weeks and measured food cravings pre-intervention and post-intervention. Our final eight studies mostly used the Food Craving Inventory. Other comparable methods were converted to a similar scale. We used the duration ≥12 weeks, but closest to 16 weeks for studies with multiple follow-ups and performed DerSimonian-Laird random-effects meta-analyses using the 'metafor' package in r software. RESULTS Despite heterogeneity across studies, we observed reductions in pooled effects for overall food cravings (-0.246 [-0.490, -0.001]) as well as cravings for sweet (-0.410 [-0.626, -0.194]), high-fat (-0.190 [-0.343, -0.037]), starchy (-0.288 [-0.517, -0.058]) and fast food (-0.340 [-0.633, -0.048]) in the meta-analysis. Baseline body weight, type of intervention, duration, sample size and percentage of female subjects explained the heterogeneity. CONCLUSIONS Calorie restriction is associated with reduced food cravings supporting a de-conditioning model of craving reductions. Our findings should ease the minds of clinicians concerned about increased cravings in patients undergoing calorie restriction interventions.
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Brain regions involved in ingestive behavior and related psychological constructs in people undergoing calorie restriction.
Kahathuduwa, CN, Boyd, LA, Davis, T, O'Boyle, M, Binks, M
Appetite. 2016;:348-361
Abstract
Human food intake is regulated by physiological energy homeostatic mechanisms and hedonic mechanisms. These are affected by both very short-term and longer-term calorie restriction (CR). To date, there are parallel discussions in the literature that fail to integrate across these disciplines and topics. First, much of the available neuroimaging research focusses on specific functional paradigms (e.g. reward, energy homeostasis). These paradigms often fail to consider more complex and inclusive models that examine how potential brain regions of interest interact to influence ingestion. Second, the paradigms used focus primarily on short-term CR (fasting) which has limited generalizability to clinical application. Finally, the behavioral literature, while frequently examining longer-term CR and related psychological constructs in the context of weight management (e.g. hedonic restraint, 'liking', 'wanting' and food craving), fails to adequately tie these phenomena to underlying neural mechanisms. The result is a less than complete picture of the brain's role in the complexity of the human experience of ingestion. This disconnect highlights a major limitation in the CR literature, where attempts are persistently made to exert behavioral control over ingestion, without fully understanding the complex bio behavioral systems involved. In this review we attempt to summarize all potential brain regions important for human ingestion, present a broad conceptual overview of the brain's multifaceted role in ingestive behavior, the human (psychological) experiences related to ingestion and to examine how these factors differ according to three forms of CR. These include short-term fasting, extended CR, and restrained eating. We aim to bring together the neuroimaging literature with the behavioral literature within a conceptual framework that may inform future translational research.
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Energetic interventions for healthspan and resiliency with aging.
Huffman, DM, Schafer, MJ, LeBrasseur, NK
Experimental gerontology. 2016;:73-83
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Abstract
Several behavioral and pharmacological strategies improve longevity, which is indicative of delayed organismal aging, with the most effective interventions extending both life- and healthspan. In free living creatures, maintaining health and function into old age requires resilience against a multitude of stressors. Conversely, in experimental settings, conventional housing of rodents limits exposure to such challenges, thereby obscuring an accurate assessment of resilience. Caloric restriction (CR) and exercise, as well as pharmacologic strategies (resveratrol, rapamycin, metformin, senolytics), are well established to improve indices of health and aging, but some paradoxical effects have been observed on resilience. For instance, CR potently retards the onset of age-related diseases, and improves lifespan to a greater extent than exercise in a variety of models. However, exercise has proven more consistently beneficial to organismal resilience against a broad array of stressors, including infections, surgery, wound healing and frailty. CR can improve cellular stress defenses and protect from frailty, but also impairs the response to infections, bed rest and healing. How an intervention will impact not only longevity, health and function, but also resiliency, is critical to better understanding translational implications. Thus, organismal robustness represents a critical, albeit understudied aspect of aging, which needs more careful attention in order to better inform on how putative age-delaying strategies will impact preservation of health and function in response to stressors with aging in humans.
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A Review of the Effect of Dietary Composition on Fasting Substrate Oxidation in Healthy and Overweight Subjects.
Whelan, ME, Wright, OR, Hickman, IJ
Critical reviews in food science and nutrition. 2016;(1):146-51
Abstract
AIM: The purpose of this review was to assess existing evidence on the effects of chronic dietary macronutrient composition on substrate oxidation during a fasted state in healthy and overweight subjects. METHODS A systematic review of studies was conducted across five databases. Studies were included if they were English language studies of human adults, ≥19 years, used indirect calorimetry (ventilated hood technique), specified dietary macronutrient composition, and measured substrate oxidation. RESULTS There was no evidence that variations of a typical, non-experimental diet influenced rate or ratio of substrate utilization, however there may be an upper and lower threshold for when macronutrient composition may directly alter preferences for fuel oxidation rates during a fasted state. CONCLUSION This review indicates that macronutrient composition of a wide range of typical, non-experimental dietary fat and carbohydrate intakes has no effect on fasting substrate oxidation. This suggests that strict control of dietary intake prior to fasting indirect calorimetry measurements may be an unnecessary burden for study participants. Further research into the effects of long-term changes in isocaloric macronutrient shift is required.
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Effects of Different Dietary Interventions on Blood Pressure: Systematic Review and Meta-Analysis of Randomized Controlled Trials.
Gay, HC, Rao, SG, Vaccarino, V, Ali, MK
Hypertension (Dallas, Tex. : 1979). 2016;(4):733-9
Abstract
Previous studies have shown beneficial effects of individual dietary approaches for blood pressure (BP) control, but their relative effectiveness is not well established. We performed a systematic review of published dietary pattern interventions and estimated the aggregate BP effects through meta-analysis. PubMed, EMBASE, and Web of Science databases were searched to identify studies published between January 1, 1990 and March 1, 2015. Studies meeting specific inclusion and exclusion criteria were selected. Data were pooled using random effects meta-analysis models. Twenty-four trials with 23 858 total participants were included. The overall pooled net effect of dietary intervention on systolic BP and diastolic BP was -3.07 mm Hg (95% confidence interval, -3.85 to -2.30) and -1.81 mm Hg (95% confidence interval, -2.24 to -1.38), respectively. The Dietary Approaches to Stop Hypertension diet had the largest net effect (systolic BP, -7.62 mm Hg [95% confidence interval, -9.95 to -5.29] and diastolic BP, -4.22 mm Hg [95% confidence interval, -5.87 to -2.57]). Low-sodium; low-sodium, high-potassium; low-sodium, low-calorie; and low-calorie diets also led to significant systolic and diastolic BP reductions, whereas Mediterranean diet participants experienced a significant incremental reduction in diastolic but not systolic BP. Subgroup analysis also showed important variations in effectiveness based on duration, size, and participant demographics. In conclusion, dietary modifications are associated with clinically meaningful, though variable, reductions in BP. Some diets are more effective than others and under different circumstances, which has important implications from both clinical and public health perspectives.
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Efficacy of commercial weight-loss programs: an updated systematic review.
Gudzune, KA, Doshi, RS, Mehta, AK, Chaudhry, ZW, Jacobs, DK, Vakil, RM, Lee, CJ, Bleich, SN, Clark, JM
Annals of internal medicine. 2015;(7):501-12
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Abstract
BACKGROUND Commercial and proprietary weight-loss programs are popular obesity treatment options, but their efficacy is unclear. PURPOSE To compare weight loss, adherence, and harms of commercial or proprietary weight-loss programs versus control/education (no intervention, printed materials only, health education curriculum, or <3 sessions with a provider) or behavioral counseling among overweight and obese adults. DATA SOURCES MEDLINE and the Cochrane Database of Systematic Reviews from inception to November 2014; references identified by program staff. STUDY SELECTION Randomized, controlled trials (RCTs) of at least 12 weeks' duration; prospective case series of at least 12 months' duration (harms only). DATA EXTRACTION Two reviewers extracted information on study design, population characteristics, interventions, and mean percentage of weight change and assessed risk of bias. DATA SYNTHESIS We included 45 studies, 39 of which were RCTs. At 12 months, Weight Watchers participants achieved at least 2.6% greater weight loss than those assigned to control/education. Jenny Craig resulted in at least 4.9% greater weight loss at 12 months than control/education and counseling. Nutrisystem resulted in at least 3.8% greater weight loss at 3 months than control/education and counseling. Very-low-calorie programs (Health Management Resources, Medifast, and OPTIFAST) resulted in at least 4.0% greater short-term weight loss than counseling, but some attenuation of effect occurred beyond 6 months when reported. Atkins resulted in 0.1% to 2.9% greater weight loss at 12 months than counseling. Results for SlimFast were mixed. We found limited evidence to evaluate adherence or harms for all programs and weight outcomes for other commercial programs. LIMITATION Many trials were short (<12 months), had high attrition, and lacked blinding. CONCLUSION Clinicians could consider referring overweight or obese patients to Weight Watchers or Jenny Craig. Other popular programs, such as Nutrisystem, show promising weight-loss results; however, additional studies evaluating long-term outcomes are needed. PRIMARY FUNDING SOURCE None. ( PROSPERO CRD4201-4007155).