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The Weight Optimization Revamping Lifestyle using the Dietary Guidelines (WORLD) Study: Sustained Weight Loss Over 12 Months.
Psota, TL, Tindall, AM, Lohse, B, Miller, PE, Petersen, KS, Kris-Etherton, PM
Obesity (Silver Spring, Md.). 2020;28(7):1235-1244
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Effective long-term weight loss strategies to reduce the risk of death and diseases associated with being obese or overweight are required, as restrictive programmes are difficult to sustain, and weight loss may be heavily influenced by behavioural factors. This randomised control trial of 101 premenopausal women with obesity or overweight aimed to compare a lower-fat and moderate-fat diets, both with nutrition education for 12 months. The results showed that both treatment groups lost weight. Both groups consumed the same amount of fat but increased their diet quality. Diet quality and greater attendance at nutritional education sessions were associated with greater weight loss. Cholesterol was significantly lower in both groups, but blood pressure remained unchanged. Interestingly there were a large number of women who did not complete the trial. It was concluded that irrespective of the amount of fat consumed, nutrition education can help to achieve sustained weight loss, improve diet quality and decrease heart disease risk for at least 12 months. This study could be used by healthcare professionals to understand that recommending fat-based targets for weight loss may be ineffective and the importance of emotional and behavioural support for individuals on a weight loss regime to improve their risk for heart disease.
Abstract
OBJECTIVE This study aimed to compare two energy-restricted, nutrient-dense diets at the upper or lower ends of the dietary fat recommendation range (lower fat [20% energy from fat] versus moderate fat [35%]) on weight loss using behavioral theory-based nutrition education. METHODS A total of 101 premenopausal women with overweight or obesity were randomized to an energy-restricted lower-fat or moderate-fat diet for 1 year. Interventions included 28 behavioral theory-based nutrition education sessions plus weekly exercise sessions. RESULTS Both treatment groups experienced weight loss (-5.0 kg for lower fat and -4.3 kg for moderate fat; P < 0.0001), but there was no difference in weight loss or fat intake between groups. Total and low-density lipoprotein cholesterol decreased (-3. 4 mg/dL and -3.8 mg/dL; P < 0.05), and high-density lipoprotein cholesterol increased (1.9 mg/dL; P < 0.05) in both groups at 12 months. Diet quality, assessed by the Healthy Eating Index, increased significantly at 4 months versus baseline (70.8 [0.9] vs. 77.8 [1.0]) and was maintained through 12 months. Higher Healthy Eating Index scores were associated with greater weight loss at 4 months (r = -0.2; P < 0.05). CONCLUSIONS In the context of a well-resourced, free-living weight-loss intervention, total fat intake did not change; however, theory-based nutrition education underpinned by food-based recommendations resulted in caloric deficits, improvements in diet quality, and weight loss that was sustained for 1 year.
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Chronic Ketogenic Low Carbohydrate High Fat Diet Has Minimal Effects on Acid-Base Status in Elite Athletes.
Carr, AJ, Sharma, AP, Ross, ML, Welvaert, M, Slater, GJ, Burke, LM
Nutrients. 2018;10(2)
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The low-fat, high-carbohydrate ketogenic diet has recently been applied to the context of elite athletes to observe potential impact on performance and metabolism during exercise and rest. The aim to this study was to assess the effect of a long-term ketogenic diet on the acid-base status in elite athletes, particularly investigating whether sustained diet change caused alterations in overall acid production. Twenty-one athletes were assigned to a high carbohydrate diet, low carbohydrate diet and periodised carbohydrate availability diet for three sustained weeks. Acid-base balance was measured via blood samples at baseline and post-intervention. The main finding of this study was that a sustained ketogenic diet had no influence of acid-base status. Based on these results, the authors conclude that long-term manipulation of macronutrient intake is unlikely to influence acid-base status in this population. It is also noted that elite athletes may have an increased buffering capacity compared with the general population, and that further research should be done in different participant populations.
Abstract
Although short (up to 3 days) exposure to major shifts in macronutrient intake appears to alter acid-base status, the effects of sustained (>1 week) interventions in elite athletes has not been determined. Using a non-randomized, parallel design, we examined the effect of adaptations to 21 days of a ketogenic low carbohydrate high fat (LCHF) or periodized carbohydrate (PCHO) diet on pre- and post-exercise blood pH, and concentrations of bicarbonate (HCO₃-) and lactate (La-) in comparison to a high carbohydrate (HCHO) control. Twenty-four (17 male and 7 female) elite-level race walkers completed 21 days of either LCHF (n = 9), PCHO (n = 7), or HCHO (n = 8) under controlled diet and training conditions. At baseline and post-intervention, blood pH, blood [HCO₃-], and blood [La-] were measured before and after a graded exercise test. Net endogenous acid production (NEAP) over the previous 48-72 h was also calculated from monitored dietary intake. LCHF was not associated with significant differences in blood pH, [HCO₃-], or [La-], compared with the HCHO diet pre- or post-exercise, despite a significantly higher NEAP (mEq·day-1) (95% CI = [10.44; 36.04]). Our results indicate that chronic dietary interventions are unlikely to influence acid-base status in elite athletes, which may be due to pre-existing training adaptations, such as an enhanced buffering capacity, or the actions of respiratory and renal pathways, which have a greater influence on regulation of acid-base status than nutritional intake.
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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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Effects of Two Years of Calorie Restriction on Aerobic Capacity and Muscle Strength.
Racette, SB, Rochon, J, Uhrich, ML, Villareal, DT, DAS, SK, Fontana, L, Bhapkar, M, Martin, CK, Redman, LM, Fuss, PJ, et al
Medicine and science in sports and exercise. 2017;49(11):2240-2249
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Caloric restriction (CR) has been shown to increase lifespan and delay age-related disease in many species. As a part of the Comprehensive Assessment of Long-term Effects of Reducing Intake of Energy (CALERIE) study, this particular study aimed to determine whether long-term CR adversely affects aerobic capacity and muscle strength in 218 healthy, nonobese adults. Participants were randomised to 25% CR or control group, and a VO2max treadmill test, knee flexor and extensor strength were all measured at baseline, one year and two years. This study showed that two years of CR without a structured exercise component did not appear to compromise aerobic capacity in healthy nonobese adults.
Abstract
PURPOSE Calorie restriction (CR) improves health span and delays age-related diseases in many species. The multicenter Comprehensive Assessment of Long-term Effects of Reducing Intake of Energy (CALERIE) study was the first randomized controlled trial of CR in nonobese humans. The aim of this investigation was to determine the effects of CR on V˙O2max and muscle strength in the CALERIE trial. METHODS Healthy, normal-weight, and mildly overweight women and men (n = 218, mean ± SE age = 37.9 ± 0.5 yr) were randomized to 25% CR or an ad libitum (AL) control condition in a 2:1 allocation (143 CR, 75 AL). V˙O2max was determined with an incremental treadmill test; the strength of the knee flexors and extensors was assessed by dynamometry at baseline, 1 yr, and 2 yr. RESULTS The CR group achieved an average 11.9% ± 0.7% CR during the 2-yr intervention. Body weight decreased in CR (-7.7 ± 0.4 kg), but not AL (+0.2 ± 0.5 kg). Absolute V˙O2max (L·min) decreased at 1 and 2 yr with CR, whereas V˙O2max expressed relative to body mass increased at both time points (1 yr: +2.2 ± 0.4; 2 yr: +1.9 ± 0.5 mL·kg·min) and relative to AL. The CR group increased their treadmill test time and workload at 1 and 2 yr. Strength results in CR were similar, with decreases in absolute flexor and extensor strength, but increases when expressed relative to body mass. No changes were observed for V˙O2max expressed relative to lean body mass or leg lean mass. CONCLUSIONS Two years of modest CR without a structured exercise component did not appear to compromise aerobic capacity in healthy nonobese adults. The clinical implications of the observed changes in V˙O2max and muscle strength will be important to explore in future studies.
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Gastrointestinal permeability during exercise: effects of aspirin and energy-containing beverages.
Lambert, GP, Broussard, LJ, Mason, BL, Mauermann, WJ, Gisolfi, CV
Journal of applied physiology (Bethesda, Md. : 1985). 2001;90(6):2075-80
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Many athletes use aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs) for analgesia. This study of 17 subjects aimed to assess whether the use of aspirin with prolonged exercise could increase gastrointestinal permeability. It also aimed to examine whether consumption of a carbohydrate-containing or a carbohydrate and glutamine-containing beverage could reduce this effect. Authors concluded that acute aspirin consumption before prolonged exercise could increase gastroduodenal and intestinal permeability. They also indicated that gastroduodenal permeability was significantly decreased by the ingestion of carbohydrate-containing beverages and that consumption of carbohydrate containing glutamine beverage provided no additional benefits than the carbohydrate alone beverage.
Abstract
The purpose of this study was to determine whether aspirin (A) ingestion combined with prolonged exercise increases gastrointestinal permeability and whether consumption of a carbohydrate-containing (CHO) or a CHO + glutamine-containing (CHO+G) beverage would reduce this effect. Seventeen subjects completed six experiments. They ingested A (1,300 mg) or placebo (P) pills the evening before and before running 60 min at 70% maximal oxygen uptake. Also, before running they ingested a solution containing 5 g lactulose (L), 5 g sucrose (S), and 2 g rhamnose (R). During each trial, either a 6% CHO beverage, a 6% CHO+G (0.6%; 41 mM) beverage, or a water placebo (WP) was consumed. For 4 h after a run, all urine was collected to measure urinary excretion of L, R, and S. S excretion (percentage of dose ingested; measure of gastroduodenal permeability) was significantly greater (P < 0.05) during the A trial while the subjects drank the WP compared with all other trials. Administration of A also significantly increased L/R (measure of intestinal permeability) for the CHO and WP trials compared with all P trials. Ingestion the CHO or CHO+G beverages significantly reduced S excretion and L excretion when A was administered, but it did not reduce L/R. These results indicate that gastroduodenal and intestinal permeability increase after A ingestion during prolonged running and that ingestion of a CHO beverage attenuates the gastroduodenal effect but not the intestinal effect. Furthermore, addition of G to the CHO beverage provided no additional benefit in reducing gastroduodenal or intestinal permeability.