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Effect of High-Intensity Interval Training, Moderate Continuous Training, or Guideline-Based Physical Activity Advice on Peak Oxygen Consumption in Patients With Heart Failure With Preserved Ejection Fraction: A Randomized Clinical Trial.
Mueller, S, Winzer, EB, Duvinage, A, Gevaert, AB, Edelmann, F, Haller, B, Pieske-Kraigher, E, Beckers, P, Bobenko, A, Hommel, J, et al
JAMA. 2021;325(6):542-551
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Heart failure with preserved ejection fraction (HFpEF) is a condition in which the heart's lower left chamber is less able to pump blood due to stiffness. The prevalence of HFpEF is high among the elderly. Endurance exercise is known to increase peak oxygen consumption (Vo2). This prospective, randomised, controlled, three-armed, multi-centre trial aimed to understand the effects of endurance training in older people with HFpEF at 3 and 12 months. In this study, 180 sedentary patients with HFpEF were randomly assigned to high-intensity interval training, moderate continuous training, or control of home-based tele-guideline physical activity advice. The study found no statistically significant difference in changes in V̇o2 between high-intensity interval and moderate continuous training, and neither group met the clinically significant difference of 2.5 mL/kg/min compared with the guideline control. Diastolic function or natriuretic peptides did not change significantly in any group. Adherence level was lower among elderly patients, and there were serious adverse effects in patients with HFpEE. Healthcare professionals can use the findings of this study to understand the impact and adverse effects of endurance training at different intensities in patients with HFpEE.
Abstract
Importance: Endurance exercise is effective in improving peak oxygen consumption (peak V̇o2) in patients with heart failure with preserved ejection fraction (HFpEF). However, it remains unknown whether differing modes of exercise have different effects. Objective: To determine whether high-intensity interval training, moderate continuous training, and guideline-based advice on physical activity have different effects on change in peak V̇o2 in patients with HFpEF. Design, Setting, and Participants: Randomized clinical trial at 5 sites (Berlin, Leipzig, and Munich, Germany; Antwerp, Belgium; and Trondheim, Norway) from July 2014 to September 2018. From 532 screened patients, 180 sedentary patients with chronic, stable HFpEF were enrolled. Outcomes were analyzed by core laboratories blinded to treatment groups; however, the patients and staff conducting the evaluations were not blinded. Interventions: Patients were randomly assigned (1:1:1; n = 60 per group) to high-intensity interval training (3 × 38 minutes/week), moderate continuous training (5 × 40 minutes/week), or guideline control (1-time advice on physical activity according to guidelines) for 12 months (3 months in clinic followed by 9 months telemedically supervised home-based exercise). Main Outcomes and Measures: Primary end point was change in peak V̇o2 after 3 months, with the minimal clinically important difference set at 2.5 mL/kg/min. Secondary end points included changes in metrics of cardiorespiratory fitness, diastolic function, and natriuretic peptides after 3 and 12 months. Results: Among 180 patients who were randomized (mean age, 70 years; 120 women [67%]), 166 (92%) and 154 (86%) completed evaluation at 3 and 12 months, respectively. Change in peak V̇o2 over 3 months for high-intensity interval training vs guideline control was 1.1 vs -0.6 mL/kg/min (difference, 1.5 [95% CI, 0.4 to 2.7]); for moderate continuous training vs guideline control, 1.6 vs -0.6 mL/kg/min (difference, 2.0 [95% CI, 0.9 to 3.1]); and for high-intensity interval training vs moderate continuous training, 1.1 vs 1.6 mL/kg/min (difference, -0.4 [95% CI, -1.4 to 0.6]). No comparisons were statistically significant after 12 months. There were no significant changes in diastolic function or natriuretic peptides. Acute coronary syndrome was recorded in 4 high-intensity interval training patients (7%), 3 moderate continuous training patients (5%), and 5 guideline control patients (8%). Conclusions and Relevance: Among patients with HFpEF, there was no statistically significant difference in change in peak V̇o2 at 3 months between those assigned to high-intensity interval vs moderate continuous training, and neither group met the prespecified minimal clinically important difference compared with the guideline control. These findings do not support either high-intensity interval training or moderate continuous training compared with guideline-based physical activity for patients with HFpEF. Trial Registration: ClinicalTrials.gov Identifier: NCT02078947.
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Comparing Acute, High Dietary Protein and Carbohydrate Intake on Transcriptional Biomarkers, Fuel Utilisation and Exercise Performance in Trained Male Runners.
Furber, M, Pyle, S, Roberts, M, Roberts, J
Nutrients. 2021;13(12)
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Dietary modification to improve exercise endurance has become a popular strategy. The reduction of carbohydrates to enhance adaptations due to training has been shown on a cellular level. In low carbohydrate diets, fat is the usual substitute, however long-term adherence to this is often difficult. Using protein instead of fat may be an alternative, but there is little research on this. This study aimed to investigate the impact of a short-term high-protein, reduced carbohydrate diet compared to a high-carbohydrate diet in combination with endurance running on exercise performance and cellular adaptations. The results showed that any cellular adaptations were due to fuel availability, rather than the fuel type and that a high protein diet compromised high intensity exercise performance. It was concluded that a high-protein, low-carbohydrate diet in combination with endurance training is of no benefit to endurance running performance. This study could be used by healthcare professionals to recommend that athletes and especially runners who wish to improve endurance do not switch to a high-protein, low carbohydrate diet and that other dietary modifications are investigated.
Abstract
Manipulating dietary macronutrient intake may modulate adaptive responses to exercise, and improve endurance performance. However, there is controversy as to the impact of short-term dietary modification on athletic performance. In a parallel-groups, repeated measures study, 16 trained endurance runners (maximal oxygen uptake (V˙O2max): 64.2 ± 5.6 mL·kg-1·min-1) were randomly assigned to, and provided with, either a high-protein, reduced-carbohydrate (PRO) or a high-carbohydrate (CHO) isocaloric-matched diet. Participants maintained their training load over 21-consecutive days with dietary intake consisting of 7-days habitual intake (T1), 7-days intervention diet (T2) and 7-days return to habitual intake (T3). Following each 7-day dietary period (T1-T3), a micro-muscle biopsy was taken for assessment of gene expression, before participants underwent laboratory assessment of a 10 km treadmill run at 75% V˙O2max, followed by a 95% V˙O2max time to exhaustion (TTE) trial. The PRO diet resulted in a modest change (1.37-fold increase, p = 0.016) in AMPK expression, coupled with a significant increase in fat oxidation (0.29 ± 0.05 to 0.59 ± 0.05 g·min-1, p < 0.0001). However, a significant reduction of 23.3% (p = 0.0003) in TTE post intervention was observed; this reverted back to pre levels following a return to the habitual diet. In the CHO group, whilst no change in sub-maximal fuel utilisation occurred at T2, a significant 6.5% increase in TTE performance (p = 0.05), and a modest, but significant, increase in AMPK (p = 0.042) and PPAR (p = 0.029) mRNA expression compared to T1 were observed; with AMPK (p = 0.011) and PPAR (p = 0.044) remaining significantly elevated at T3. In conclusion, a 7-day isocaloric high protein diet significantly compromised high intensity exercise performance in trained runners with no real benefit on gene markers of training adaptation. A significant increase in fat oxidation during submaximal exercise was observed post PRO intervention, but this returned to pre levels once the habitual diet was re-introduced, suggesting that the response was driven via fuel availability rather than cellular adaptation. A short-term high protein, low carbohydrate diet in combination with endurance training is not preferential for endurance running performance.
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Impact of changes in physical activity or BMI on risk of heart failure in women - the prospective population study of women in Gothenburg.
Halldin, AK, Lissner, L, Lernfelt, B, Björkelund, C
Scandinavian journal of primary health care. 2020;38(1):56-65
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Heart failure (HF) is a severe and progressive condition with poor prognosis. Obesity is a risk factor for HF. The aim of this study was to investigate the impact of change in physical activity or change in body mass index on the risk of later developing HF in women without a previous diagnosis of HF. This study is prospective longitudinal study which includes 1749 healthy women from the Prospective Population Study of Women in Gothenburg. Results indicate that gaining weight in early middle age is more harmful than gaining weight later in life, with regard to the risk of developing HF later in life. Furthermore, reduced risk of future HF in healthy women may be achieved by remaining physically active from young middle age and throughout life or by increasing the level of physical activity. Authors conclude that the role of physical activity in preventing the development of obesity must be taken into account.
Abstract
Objective: To longitudinally evaluate the impact of change in physical activity or change in body mass index (BMI) over time on the risk of developing heart failure (HF) in women without a previous diagnosis of HF.Design and setting: Longitudinal, observational, prospective study of women in Gothenburg, Sweden. Data on BMI and level of physical activity were collected from examinations 1968-1992 and hospital diagnoses and mortality data were ascertained from 1980 to 2012.Subjects: Data were obtained from 1749 women included in the Prospective Population Study of Women in Gothenburg.Main outcome measures: Hazard ratio (HR) for HF was calculated, using a Cox regression model.Results: Women with stable high physical activity during 1968-1980 and 1980-1992 reduced their risk of subsequent HF compared to the non-active women (for 1968-1980 HR 0.66, 95% Confidence Interval (CI) 0.44-0.99 and for 1980-1992 HR 0.47, 95% CI 0.29-0.74). Women with increasing levels of physical activity during 1980-1992 reduced their risk of HF compared to the non-active women (HR 0.40, 95% CI 0.22-0.72). Increase in BMI from overweight to obesity during 1968-1980 predicted increased risk of developing HF (HR 1.93, 95% CI 1.18-3.14).Conclusions: Reduced risk of future HF in healthy women may be achieved by remaining physically active from young middle age and throughout life or by increasing the level of physical activity. This is particularly important for sedentary women in middle age. The role of physical activity in preventing the development of obesity must be taken into account.Key pointsA sedentary lifestyle and obesity are risk factors for developing heart failure (HF) in women.The risk of developing HF may be reduced by increasing the level of activity in sedentary middle-aged women.For younger women, avoiding obesity is most important to reduce the risk of later HF.Primary care has a key role in guiding women towards the most effective lifestyle changes to prevent development of HF.
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Referral to Slimming World in UK Stop Smoking Services (SWISSS) versus stop smoking support alone on body weight in quitters: results of a randomised controlled trial.
Lycett, D, Aveyard, P, Farmer, A, Lewis, A, Munafò, M
BMJ open. 2020;10(1):e032271
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Weight gain is a well-known consequence of smoking cessation. The aim of this study was to compare standard stop smoking behavioural support with an intervention that, in addition to providing standard stop smoking support, included personalised weight management support, provided by Slimming World. This study is a parallel group, individually randomised controlled trial. Participants were randomised (1:1) to usual care or Slimming World with usual care. Stop smoking advisors were unaware of the randomisation sequence. Results showed that referral to the Slimming World programme plus usual stop smoking support achieved significantly less weight gain than usual stop smoking support alone. Furthermore, percentage quit was no worse in the treatment than the control group. Authors conclude that referral to a behavioural weight loss programme may be a pragmatic option within stop smoking clinics.
Abstract
INTRODUCTION Most people who stop smoking gain weight. Dietary modification may seem an obvious solution, but food restriction may increase cigarette craving and smoking relapse. TRIAL DESIGN An unblinded parallel randomised controlled trial. METHODS Participants were adult smokers with a body mass index greater or equal to 23 kg/m2. Setting was National Health Service commissioned Stop Smoking Services, interventions were referral to a commercial weight management programme, plus stop smoking support (treatment group), compared with stop smoking support alone (control group). Objective was to compare weight change between interventions in smoking abstainers and not abstinent rates in all. Primary outcome was change in weight (kg) at 12 weeks. Randomisation sequence was computer generated and concealed until allocation. RESULTS Seventy-six participants were recruited, 37 were randomised to the treatment group and 39 to the control group. Change in weight was analysed in long-term abstainers (13 treatment, 14 control) only because the aim was to prevent weight gain associated with smoking cessation. Abstinence was analysed on an intention-to-treat basis (37 treatment, 39 control). At 12 weeks weight gain was less in the treatment than the control group with an adjusted mean difference of -2.3 kg 95% CI (-4.4 to -0.1). Craving scores were lower (Mood and Physical Symptoms Scale craving domain -1.6 (-2.7 to -0.5)) and quit rates were higher in the treatment than the control group (32% vs 21%), although the trial was not powered to superiority in cravings and quit rates. No adverse events or side effects were reported. CONCLUSION In people who are obese and want to quit smoking, these data provide modest encouragement that providing weight management at the time of quitting may be helpful. Those who are not obese, but who are informed about potential weight gain during their quit attempt, were uninterested in a weight management programme. TRIAL REGISTRATION NUMBER ISRCTN65705512.
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Brain-Behavior-Immune Interaction: Serum Cytokines and Growth Factors in Patients with Eating Disorders at Extremes of the Body Mass Index (BMI) Spectrum.
Caroleo, M, Carbone, EA, Greco, M, Corigliano, DM, Arcidiacono, B, Fazia, G, Rania, M, Aloi, M, Gallelli, L, Segura-Garcia, C, et al
Nutrients. 2019;11(9)
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Eating disorders such as anorexia, binge eating and night-time eating cause great fluctuations in body mass and have also been shown to alter the immune system, and more specifically markers of inflammation called cytokines. In this observational study of 90 patients with known eating disorders, the researchers tried to identify how much BMI, ‘underweightness’ and malnutrition influenced the body’s pro-inflammatory response and upset the normal immune response. They found that many inflammatory cytokines were elevated in the blood samples taken, a likely response to the conditions of stress in the body. These cytokines are known to interact with the nervous system and were also influenced by other common symptoms such as depression. They were able to group the differences in cytokines for anorexia nervosa, binge-eating disorder, post-dinner eating, night-eating, sweet-eating and fasting. These markers of dysfunctional eating behaviours may help form part of a therapeutic approach to treating eating disorders based on supporting the immune response and reducing inflammation to stabilise metabolic processes. Future studies in a larger population of patients is necessary to determine the relevance of these findings.
Abstract
Alterations of the immune system are known in eating disorders (EDs), however the importance of cytokine balance in this context has not been clarified. We compared cytokines and growth factors at opposite ends of BMI ranges, in 90 patients classified in relation to BMI, depressive and EDs comorbidities. Serum concentrations of interleukin (IL)-1α, IL-1β, IL-2, IL-4, IL-6, IL-8, IL-10, interferon-gamma (IFN-γ), tumor necrosis factor-alpha (TNF-α), monocyte chemoattractant protein-1 (MCP-1), vascular endothelial growth factor (VEGF), and epidermal growth factor (EGF) were determined by a biochip analyzer (Randox Labs). Differences were calculated through ANOVA. Possible predictors of higher cytokine levels were evaluated through regression analysis. IL-1α, IL-10, EGF, and IFN-γ were altered individuals with anorexia nervosa (AN) and binge eating disorder (BED). Night-eating was associated with IL-8 and EGF levels, IL-10 concentrations with post-dinner eating and negatively with sweet-eating, long fasting with higher IFN-γ levels. IL-2 increase was not linked to EDs, but to the interaction of depression and BMI. Altogether, for the first time, IL-1α, IL-10, EGF, and IFN-γ were shown to differ between AN and HCs, and between AN and individuals with obesity with or without BED. Only IL-2 was influenced by depression. Dysfunctional eating behaviors predicted abnormal concentrations of IL-10, EGF, IL-8 and IFN-γ.
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What is the effect of a Mediterranean compared with a Fast Food meal on the exercise induced adipokine changes? A randomized cross-over clinical trial.
Silva, D, Moreira, R, Beltrão, M, Sokhatska, O, Montanha, T, Pizarro, A, Garcia-Larsen, V, Villegas, R, Delgado, L, Moreira, P, et al
PloS one. 2019;14(4):e0215475
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Unhealthy dietary intake and sedentary behaviour in a genetically susceptible individual have been associated with adipokine dysregulation (adipokines are small proteins secreted by the fat tissue) resulting both in adverse metabolic and immune responses. The aim of this study was to evaluate the effect of a Mediterranean (MdM) compared with a Fast Food (FFM) iso-energy meal on the acute exercise-induced adipokine changes. The study is a double-blind randomised crossover clinical trial. Participants (n = 46) were randomly assigned to the intervention order in a double-blinded fashion, stratified by asthma diagnosis. Outcomes were measured blinded to the participant’s allocation order. Results indicate that MdM may blunt the adipsin (an adipokine) immediate response and potentiate its exercise induced increase in comparison with a FFM. MdM slightly attenuated the exercise induced cortisol increase. Authors conclude that their findings highlight the importance of the pre-exercise dietary intake on both the immune and metabolic response to acute exercise.
Abstract
BACKGROUND Adipose tissue-derived adipokines are pro-inflammatory cytokines involved in metabolic-related diseases and can be influenced by diet and exercise. We aimed to compare the effect of a Mediterranean (MdM) compared with Fast Food (FFM) meal on the exercise induced adipokines changes. METHODS In a double blinded cross over trial, 46 participants were randomly assigned to one of two standardized iso-energy pre-exercise meals: FFM or MdM-type. Three hours after each meal, participants completed a treadmill exercise test (EC). Serum adiponectin, resistin, PAI-1, lipocalin-2/NGAL and adipsin were determined by Luminex magnetic bead immunoassay. Wilcoxon signed rank test compared changes before/after meal and before/after EC and a linear mixed model evaluated the effect of meals on the adipokine response to exercise, adjusted for confounders. RESULTS Thirty-nine participants (mean age of 25, with a standard deviation of 5 years) completed the trial (56% females). For both interventions, a significant reduction of adipsin after each meal and a significant increase of lipocalin, PAI-1, adipsin and resistin, after exercise was observed. When exercise was preceded by a MdM meal a higher increase in adipsin levels was seen. CONCLUSION Acute exercise induced an increase of circulatory levels of adipsin, resistin, lipocalin and PAI-1, but not adiponectin. A pre-exercise Mediterranean meal potentiated the increase of adipsin after the exercise test, which possibly relates to the immune regulatory role of adipsin. These changes suggest a cross-talk between the immune and metabolic immediate response to exercise and its modulation by the pre-exercise diet composition.
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Health Biomarkers in Adults Are More Closely Linked to Diet Quality Attributes Than to Plant-Based Diet Categorization.
Mayra, S, Ugarte, N, Johnston, CS
Nutrients. 2019;11(6)
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Plant-based diets rich in fruits, vegetables, whole grains, nuts, and legumes are consistently linked to reduced risk for chronic disease, improved cognition, and longevity. The aim of the study was to examine the diet quality and blood metabolites of vegetarian and omnivore adults to determine adherence to plant-based diets compared to high-quality eating patterns. The study is a cross-sectional investigation. Thirty-three participants (17 vegetarians: 3 men/14 women; 16 omnivores: 3 men/13 women) aged between 18 and 65 years were enrolled for the study. Results indicate the health biomarkers did not differ between vegetarians and omnivores matched for gender, age, and adiposity. However, when participants were regrouped by low-quality versus high-quality diets, data suggests that several common health biomarkers are more closely aligned with diet quality attributes than with plant-based diet categorisation. Authors conclude that healthcare practitioners should emphasize diet quality in their messages to their clients and discuss the importance of eating whole, minimally processed foods with less added fat and sugars.
Abstract
Although plant-based diets are promoted for healthy outcomes, these diets are not synonymous with high-quality diets. Plant-based diets can include highly processed, less healthful foods, including savory snacks, pastries, and sugary fruit drinks. This cross-sectional study examined the diet quality of vegetarian and omnivorous adults, matched for gender, age, and adiposity, and related diet quality to standard health biomarkers. Diet quality was assessed using the Rapid Eating and Activity Assessment for Participants Short Version questionnaire. Participants (17 vegetarians and 16 omnivores; 28.2 ± 8.9 years; 22.5 ± 2.7 kg/m2) were non-smokers and healthy by self-report. The median duration of adherence to the vegetarian diet was 27 months. Physical activity level and diet quality did not differ significantly between diet groups. Moreover, health biomarkers did not differ by diet groups. When participants were regrouped by low versus high diet quality, health biomarkers differed significantly between groups for fasting insulin, HOMA-IR, triglyceride (TG)/HDL ratio, and blood folate, with more favorable levels in the group with high diet quality. These data suggest that health biomarkers more closely align with diet quality attributes than with plant-based diet categorization. Thus, messaging focused on healthy diet attributes may lead to better health outcomes than the simple promotion of plant-based diets.
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Effect of tai chi versus aerobic exercise for fibromyalgia: comparative effectiveness randomized controlled trial.
Wang, C, Schmid, CH, Fielding, RA, Harvey, WF, Reid, KF, Price, LL, Driban, JB, Kalish, R, Rones, R, McAlindon, T
BMJ (Clinical research ed.). 2018;360:k851
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Fibromyalgia is a complex disorder, characterised by chronic widespread musculoskeletal pain, fatigue, sleep problems and depression. Conventional treatment is multidisciplinary, including medication, exercise and CBT. This randomised, single-blinded trial aimed to determine the effectiveness of regular Tai Chi practice when compared to the standard recommended exercise, aerobic training. 226 adults diagnosed with fibromyalgia were randomly assigned to either 24 weeks of supervised aerobic exercise or 12 or 24 weeks of Tai Chi classes. A standard fibromyalgia impact questionnaire was used to assess changes in pain and quality of life measures, along with patient perception of various aspects of their condition. The study found that Fibromyalgia Impact Questionnaire scores improved across all treatment groups, however the 24-week Tai Chi group saw a statistically significant greater improvement than the aerobic group. In addition, those patients on the 24-week Tai Chi programme experienced greater improvement than those on the 12-week Tai Chi programme. There was also higher attendance and fewer drop-outs in the Tai Chi groups in comparison to the aerobic exercise group. Tai Chi could therefore be considered as an alternative to aerobic exercise in a multi-disciplinary approach to fibromyalgia treatment.
Abstract
OBJECTIVES To determine the effectiveness of tai chi interventions compared with aerobic exercise, a current core standard treatment in patients with fibromyalgia, and to test whether the effectiveness of tai chi depends on its dosage or duration. DESIGN Prospective, randomized, 52 week, single blind comparative effectiveness trial. SETTING Urban tertiary care academic hospital in the United States between March 2012 and September 2016. PARTICIPANTS 226 adults with fibromyalgia (as defined by the American College of Rheumatology 1990 and 2010 criteria) were included in the intention to treat analyses: 151 were assigned to one of four tai chi groups and 75 to an aerobic exercise group. INTERVENTIONS Participants were randomly assigned to either supervised aerobic exercise (24 weeks, twice weekly) or one of four classic Yang style supervised tai chi interventions (12 or 24 weeks, once or twice weekly). Participants were followed for 52 weeks. Adherence was rigorously encouraged in person and by telephone. MAIN OUTCOME MEASURES The primary outcome was change in the revised fibromyalgia impact questionnaire (FIQR) scores at 24 weeks compared with baseline. Secondary outcomes included changes of scores in patient's global assessment, anxiety, depression, self efficacy, coping strategies, physical functional performance, functional limitation, sleep, and health related quality of life. RESULTS FIQR scores improved in all five treatment groups, but the combined tai chi groups improved statistically significantly more than the aerobic exercise group in FIQR scores at 24 weeks (difference between groups=5.5 points, 95% confidence interval 0.6 to 10.4, P=0.03) and several secondary outcomes (patient's global assessment=0.9 points, 0.3 to 1.4, P=0.005; anxiety=1.2 points, 0.3 to 2.1, P=0.006; self efficacy=1.0 points, 0.5 to 1.6, P=0.0004; and coping strategies, 2.6 points, 0.8 to 4.3, P=0.005). Tai chi treatment compared with aerobic exercise administered with the same intensity and duration (24 weeks, twice weekly) had greater benefit (between group difference in FIQR scores=16.2 points, 8.7 to 23.6, P<0.001). The groups who received tai chi for 24 weeks showed greater improvements than those who received it for 12 weeks (difference in FIQR scores=9.6 points, 2.6 to 16.6, P=0.007). There was no significant increase in benefit for groups who received tai chi twice weekly compared with once weekly. Participants attended the tai chi training sessions more often than participants attended aerobic exercise. The effects of tai chi were consistent across all instructors. No serious adverse events related to the interventions were reported. CONCLUSION Tai chi mind-body treatment results in similar or greater improvement in symptoms than aerobic exercise, the current most commonly prescribed non-drug treatment, for a variety of outcomes for patients with fibromyalgia. Longer duration of tai chi showed greater improvement. This mind-body approach may be considered a therapeutic option in the multidisciplinary management of fibromyalgia. TRIAL REGISTRATION ClinicalTrials.gov NCT01420640.
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Effects of Low Versus Moderate Glycemic Index Diets on Aerobic Capacity in Endurance Runners: Three-Week Randomized Controlled Crossover Trial.
Durkalec-Michalski, K, Zawieja, EE, Zawieja, BE, Jurkowska, D, Buchowski, MS, Jeszka, J
Nutrients. 2018;10(3)
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During athletic performance, adequate amounts of carbohydrates are required to prolong the onset of fatigue. Research on whether the glycaemic index (GI) of ingested carbohydrates effects performance has been explored but has produced equivocal results. The aim of this randomised crossover study was to assess the effect of low- and moderate- GI diets on the aerobic capacity and endurance performance in 21 runners. Participants consumed a low- and moderate- GI, high carbohydrate and nutrient balanced diets for three weeks each with a two-week washout period. Aerobic capacity and body composition were measured at the beginning and end of each diet period through various athletic performance tests. This study found that after a low-GI, high-carbohydrate diet, improvements were seen in time to exhaustion and running performance. Gas exchange was improved by both diets. The low-GI carbohydrate diet helped athletes to maintain a more stable blood glucose concentration during exertion tests. Based on these results the authors suggest considering GI when planning a diet for performance athletes, and also urge further research be completed to better understand the effects of long-term GI diets with regards to exercise performance.
Abstract
The glycemic index (GI) of ingested carbohydrates may influence substrate oxidation during exercise and athletic performance. Therefore, the aim of this study was to assess the effect of low- and moderate-GI three-week diets on aerobic capacity and endurance performance in runners. We conducted a randomized crossover feeding study of matched diets differing only in GI (low vs. moderate) in 21 endurance-trained runners. Each participant consumed both, low- (LGI) and moderate-GI (MGI) high-carbohydrate (~60%) and nutrient-balanced diets for three weeks each. At the beginning and end of each diet, participants had their aerobic capacity and body composition measured and performed a 12-min running test. After LGI, time to exhaustion during incremental cycling test (ICT) and distance covered in the 12-min run were significantly increased. The MGI diet led to an increase in maximal oxygen uptake ( V ˙ O₂max), but no performance benefits were found after the MGI diet. The LGI and MGI diets improved time and workload at gas exchange threshold (GET) during ICT. The results indicate that a three-week high-carbohydrate LGI diet resulted in a small but significant improvement in athletic performance in endurance runners. Observed increase in V ˙ O₂max on MGI diet did not affect performance.
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Randomised trial of coconut oil, olive oil or butter on blood lipids and other cardiovascular risk factors in healthy men and women.
Khaw, KT, Sharp, SJ, Finikarides, L, Afzal, I, Lentjes, M, Luben, R, Forouhi, NG
BMJ open. 2018;8(3):e020167
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Blood lipids is a term used for fatty substances found in the blood such as cholesterol and triglycerides. When these fatty substances are above a normal level it may increase an individual’s risk factors for coronary heart diseases. A diet high in saturated fats is linked to an increased amount of these fats in the blood. Recent renewed interest in the health effects of saturated fats based on their composition (long chain, medium chain, and short chain) brought about this randomised control trial. The aim of the study was to compare the effects of butter, extra virgin coconut oil and olive oil on blood lipids. The study population were men and women aged between 50 and 70 years who did not have any known medical history of heart disease or were on any medication related to heart disease. At the end of the four week trial period, significant changes in the blood lipids were observed within the three intervention groups. The concentration of LDL cholesterol in the butter group when compared with coconut oil and olive oil showed a significant increase, whilst no difference was observed in the LDL cholesterol concentration between the olive oil and coconut oil group. The concentration of HDL cholesterol in the coconut oil group increased significantly in comparison to the butter or olive oil group. However, the authors concluded that as further trials between different fatty acids and health are required, the current recommendation of the American Heart Association - to reduce saturated fat in general - is strongly recommended.
Abstract
INTRODUCTION High dietary saturated fat intake is associated with higher blood concentrations of low-density lipoprotein cholesterol (LDL-C), an established risk factor for coronary heart disease. However, there is increasing interest in whether various dietary oils or fats with different fatty acid profiles such as extra virgin coconut oil may have different metabolic effects but trials have reported inconsistent results. We aimed to compare changes in blood lipid profile, weight, fat distribution and metabolic markers after four weeks consumption of 50 g daily of one of three different dietary fats, extra virgin coconut oil, butter or extra virgin olive oil, in healthy men and women in the general population. DESIGN Randomised clinical trial conducted over June and July 2017. SETTING General community in Cambridgeshire, UK. PARTICIPANTS Volunteer adults were recruited by the British Broadcasting Corporation through their websites. Eligibility criteria were men and women aged 50-75 years, with no known history of cancer, cardiovascular disease or diabetes, not on lipid lowering medication, no contraindications to a high-fat diet and willingness to be randomised to consume one of the three dietary fats for 4 weeks. Of 160 individuals initially expressing an interest and assessed for eligibility, 96 were randomised to one of three interventions; 2 individuals subsequently withdrew and 94 men and women attended a baseline assessment. Their mean age was 60 years, 67% were women and 98% were European Caucasian. Of these, 91 men and women attended a follow-up assessment 4 weeks later. INTERVENTION Participants were randomised to extra virgin coconut oil, extra virgin olive oil or unsalted butter and asked to consume 50 g daily of one of these fats for 4 weeks, which they could incorporate into their usual diet or consume as a supplement. MAIN OUTCOMES AND MEASURES The primary outcome was change in serum LDL-C; secondary outcomes were change in total and high-density lipoprotein cholesterol (TC and HDL-C), TC/HDL-C ratio and non-HDL-C; change in weight, body mass index (BMI), waist circumference, per cent body fat, systolic and diastolic blood pressure, fasting plasma glucose and C reactive protein. RESULTS LDL-C concentrations were significantly increased on butter compared with coconut oil (+0.42, 95% CI 0.19 to 0.65 mmol/L, P<0.0001) and with olive oil (+0.38, 95% CI 0.16 to 0.60 mmol/L, P<0.0001), with no differences in change of LDL-C in coconut oil compared with olive oil (-0.04, 95% CI -0.27 to 0.19 mmol/L, P=0.74). Coconut oil significantly increased HDL-C compared with butter (+0.18, 95% CI 0.06 to 0.30 mmol/L) or olive oil (+0.16, 95% CI 0.03 to 0.28 mmol/L). Butter significantly increased TC/HDL-C ratio and non-HDL-C compared with coconut oil but coconut oil did not significantly differ from olive oil for TC/HDL-C and non-HDL-C. There were no significant differences in changes in weight, BMI, central adiposity, fasting blood glucose, systolic or diastolic blood pressure among any of the three intervention groups. CONCLUSIONS AND RELEVANCE Two different dietary fats (butter and coconut oil) which are predominantly saturated fats, appear to have different effects on blood lipids compared with olive oil, a predominantly monounsaturated fat with coconut oil more comparable to olive oil with respect to LDL-C. The effects of different dietary fats on lipid profiles, metabolic markers and health outcomes may vary not just according to the general classification of their main component fatty acids as saturated or unsaturated but possibly according to different profiles in individual fatty acids, processing methods as well as the foods in which they are consumed or dietary patterns. These findings do not alter current dietary recommendations to reduce saturated fat intake in general but highlight the need for further elucidation of the more nuanced relationships between different dietary fats and health. TRIAL REGISTRATION NUMBER NCT03105947; Results.