Caloric restriction attenuates beta-amyloid neuropathology in a mouse model of Alzheimer's disease.
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This study was designed to explore the possibility that caloric restriction (CR) may benefit Alzheimer's disease (AD) by preventing beta-amyloid (Abeta) neuropathology pivotal to the initiation and progression of the disease. We report that a CR dietary regimen prevents Abeta peptides generation and neuritic plaque deposition in the brain of a mouse model of AD neuropathology through mechanisms associated with promotion of anti-amyloidogenic alpha-secretase activity. Study findings support existing epidemiological evidence indicating that caloric intake may influence risk for AD and raises the possibility that CR may be used in preventative measures aimed at delaying the onset of AD amyloid neuropathology. (+info)
Reduced glycemic index and glycemic load diets do not increase the effects of energy restriction on weight loss and insulin sensitivity in obese men and women.
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Reducing the dietary glycemic load and the glycemic index was proposed as a novel approach to weight reduction. A parallel-design, randomized 12-wk controlled feeding trial with a 24-wk follow-up phase was conducted to test the hypothesis that a hypocaloric diet designed to reduce the glycemic load and the glycemic index would result in greater sustained weight loss than other hypocaloric diets. Obese subjects (n = 29) were randomly assigned to 1 of 3 diets providing 3138 kJ less than estimated energy needs: high glycemic index (HGI), low glycemic index (LGI), or high fat (HF). For the first 12 wk, all food was provided to subjects (feeding phase). Subjects (n = 22) were instructed to follow the assigned diet for 24 additional weeks (free-living phase). Total body weight was obtained and body composition was assessed by skinfold measurements. Insulin sensitivity was assessed by the homeostasis model (HOMA). At 12 wk, weight changes from baseline were significant in all groups but not different among groups (-9.3 +/- 1.3 kg for the HGI diet, -9.9 +/- 1.4 kg for the LGI diet, and -8.4 +/- 1.5 kg for the HF diet). All groups improved in insulin sensitivity at the end of the feeding phase of the study. During the free-living phase, all groups maintained their initial weight loss and their improved insulin sensitivity. Weight loss and improved insulin sensitivity scores were independent of diet composition. In summary, lowering the glycemic load and glycemic index of weight reduction diets does not provide any added benefit to energy restriction in promoting weight loss in obese subjects. (+info)
Metabolic and antioxidative changes in liver steatosis induced by high-fat, low-carbohydrate diet in rabbits.
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Significantly decreased amounts of carbohydrates and increase of fat in diet (Atkins' diet, Jan Kwasniewski's diet) may interfere with liver metabolism because main source of liver energy are carbohydrates. Large amount of fatty acid in diet may induce overproduction of reactive oxygen species in mitochondria because of increased oxidation and may cause steatosis. The influence of high-fat, low-carbohydrate diet (contained 14 g% protein, 25 g% fat, 8 g% carbohydrate) and compared to usual habitual diet (13 g% protein, 3 g% fat, 28 g% carbohydrate) as a control on liver function was examined in adult male rabbits. Fodder and water was ad libitum. The experiment lasted 24 weeks. At the beginning and every six weeks rabbits were weighed and blood was taken. Plasma glucose and cholesterol concentration, activity of glutamate dehydrogenase, alanine and aspartate in plasma and liver did not change. Concentrations of triacylglycerols (TG) in plasma were lower in the study group. Activity of aldolase increased in plasma and in liver in the study group while activity of sorbite dehydrogenase decreased in plasma at the end of the experiment. Malondialdehyde (MDA) concentration increased in aorta with no changes in liver and erythrocytes. Activity of glutathione peroxidase increased in erythrocytes and liver while total SOD increased only in the liver. High-fat, low-carbohydrate diet despite the lack of growth of the body mass, modifies significantly the homeostasis of carbohydrates and antioxidants in liver and enhanced production of TG in this organ, resulting in its steatosis. (+info)
Carbohydrate restriction alters lipoprotein metabolism by modifying VLDL, LDL, and HDL subfraction distribution and size in overweight men.
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To determine the effects of carbohydrate restriction (CR) with and without soluble fiber on lipoprotein metabolism, 29 men participated in a 12-wk weight loss intervention. Subjects were matched by age and BMI and randomly assigned to consume 3 g/d of either a soluble fiber supplement (n=14) or placebo (n=15) with a macronutrient energy distribution of approximately 10% carbohydrate, approximately 65% fat, and approximately 25% protein. Because the groups did not differ in any of the variables measured, all data were pooled and comparisons were made between baseline and 12 wk. After 12 wk, subjects had a mean weight loss of 7.5 kg (P<0.001), and abdominal fat was reduced by 20% (P<0.001). Plasma LDL cholesterol and triglycerides (TG) were significantly reduced by 8.9 and 38.6%, respectively. Similarly, apolipoproteins C-I (-13.8%), C-III (-21.2%) and E (-12.5%) were significantly lower after the intervention. In contrast plasma HDL-cholesterol concentrations were increased by 12% (P<0.05). Changes in plasma TG were positively correlated with reductions in large (r=0.615, P<0.01) and medium VLDL particles (r=0.432, P<0.05) and negatively correlated with LDL diameter (r=-0.489, P<0.01). Changes in trunk fat were positively correlated with medium VLDL (r=0.474, P<0.0) and small LDL (r=0.405, P<0.05) and negatively correlated with large HDL (r=-0.556, P<0.01). We conclude that weight loss induced by CR favorably alters the secretion and processing of plasma lipoproteins, rendering VLDL, LDL, and HDL particles associated with decreased risk for atherosclerosis and coronary heart disease. (+info)
Separate effects of reduced carbohydrate intake and weight loss on atherogenic dyslipidemia.
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BACKGROUND: Low-carbohydrate diets have been used to manage obesity and its metabolic consequences. OBJECTIVE: The objective was to study the effects of moderate carbohydrate restriction on atherogenic dyslipidemia before and after weight loss and in conjunction with a low or high dietary saturated fat intake. DESIGN: After 1 wk of consuming a basal diet, 178 men with a mean body mass index (in kg/m(2)) of 29.2 +/- 2.0 were randomly assigned to consume diets with carbohydrate contents of 54% (basal diet), 39%, or 26% of energy and with a low saturated fat content (7-9% of energy); a fourth group consumed a diet with 26% of energy as carbohydrate and 15% as saturated fat. After 3 wk, the mean weight loss (5.12 +/- 1.83 kg) was induced in all diet groups by a reduction of approximately 1000 kcal/d for 5 wk followed by 4 wk of weight stabilization. RESULTS: The 26%-carbohydrate, low-saturated-fat diet reduced triacylglycerol, apolipoprotein B, small LDL mass, and total:HDL cholesterol and increased LDL peak diameter. These changes were significantly different from those with the 54%-carbohydrate diet. After subsequent weight loss, the changes in all these variables were significantly greater and the reduction in LDL cholesterol was significantly greater with the 54%-carbohydrate diet than with the 26%-carbohydrate diet. With the 26%-carbohydrate diet, lipoprotein changes with the higher saturated fat intakes were not significantly different from those with the lower saturated fat intakes, except for LDL cholesterol, which decreased less with the higher saturated fat intake because of an increase in mass of large LDL. CONCLUSIONS: Moderate carbohydrate restriction and weight loss provide equivalent but nonadditive approaches to improving atherogenic dyslipidemia. Moreover, beneficial lipid changes resulting from a reduced carbohydrate intake were not significant after weight loss. (+info)
Ketogenic low-carbohydrate diets have no metabolic advantage over nonketogenic low-carbohydrate diets.
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BACKGROUND: Low-carbohydrate diets may promote greater weight loss than does the conventional low-fat, high-carbohydrate diet. OBJECTIVE: We compared weight loss and biomarker change in adults adhering to a ketogenic low-carbohydrate (KLC) diet or a nonketogenic low-carbohydrate (NLC) diet. DESIGN: Twenty adults [body mass index (in kg/m(2)): 34.4 +/- 1.0] were randomly assigned to the KLC (60% of energy as fat, beginning with approximately 5% of energy as carbohydrate) or NLC (30% of energy as fat; approximately 40% of energy as carbohydrate) diet. During the 6-wk trial, participants were sedentary, and 24-h intakes were strictly controlled. RESULTS: Mean (+/-SE) weight losses (6.3 +/- 0.6 and 7.2 +/- 0.8 kg in KLC and NLC dieters, respectively; P = 0.324) and fat losses (3.4 and 5.5 kg in KLC and NLC dieters, respectively; P = 0.111) did not differ significantly by group after 6 wk. Blood beta-hydroxybutyrate in the KLC dieters was 3.6 times that in the NLC dieters at week 2 (P = 0.018), and LDL cholesterol was directly correlated with blood beta-hydroxybutyrate (r = 0.297, P = 0.025). Overall, insulin sensitivity and resting energy expenditure increased and serum gamma-glutamyltransferase concentrations decreased in both diet groups during the 6-wk trial (P < 0.05). However, inflammatory risk (arachidonic acid:eicosapentaenoic acid ratios in plasma phospholipids) and perceptions of vigor were more adversely affected by the KLC than by the NLC diet. CONCLUSIONS: KLC and NLC diets were equally effective in reducing body weight and insulin resistance, but the KLC diet was associated with several adverse metabolic and emotional effects. The use of ketogenic diets for weight loss is not warranted. (+info)
Comparative effects of a low-carbohydrate diet and exercise plus a low-carbohydrate diet on muscle sarcoplasmic reticulum responses in males.
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We employed a glycogen-depleting session of exercise followed by a low-carbohydrate (CHO) diet to investigate modifications that occur in muscle sarcoplasmic reticulum (SR) Ca(2+)-cycling properties compared with low-CHO diet alone. SR properties were assessed in nine untrained males [peak aerobic power (Vo(2 peak)) = 43.6 +/- 2.6 (SE) ml.kg(-1).min(-1)] during prolonged cycle exercise to fatigue performed at approximately 58% Vo(2 peak) after 4 days of low-CHO diet (Lo CHO) and after glycogen-depleting exercise plus 4 days of low-CHO (Ex+Lo CHO). Compared with Lo CHO, Ex+Lo CHO resulted in 12% lower (P < 0.05) resting maximal Ca(2+)-ATPase activity (V(max) = 174 +/- 12 vs. 153 +/- 10 micromol.g protein(-1).min(-1)) and smaller reduction in V(max) induced during exercise. A similar effect was observed for Ca(2+) uptake. The Hill coefficient, defined as slope of the relationship between cytosolic free Ca(2+) concentration and Ca(2+)-ATPase activity, was higher (P < 0.05) at rest (2.07 +/- 0.15 vs. 1.90 +/- 0.10) with Ex+Lo CHO, an effect that persisted throughout the exercise. The coupling ratio, defined as the ratio of Ca(2+) uptake to V(max), was 23-30% elevated (P < 0.05) at rest and during the first 60 min of exercise with Ex+Lo CHO. The approximately 27 and 34% reductions (P < 0.05) in phase 1 and phase 2 Ca(2+) release, respectively, observed during exercise with Lo CHO were not altered by Ex+Lo CHO. These results indicate that when prolonged exercise precedes a short-term Lo CHO diet, Ca(2+) sequestration properties and efficiency are improved compared with those during Lo CHO alone. (+info)
Low-carbohydrate diets.
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Americans spend dollar 33 billion annually on weight loss products and services, and a large portion of this money is spent on low-carbohydrate diets. Because of their higher protein and fat content and lower fiber and carbohydrate content, concerns have been raised about the potential health consequences of low-carbohydrate diets. Published long-term data are lacking. Short-term studies comparing traditional low-fat diets with low-carbohydrate diets found lower triglyceride levels, higher high-density lipoprotein cholesterol levels, similar low-density lipoprotein cholesterol levels, and lower A1C levels in persons on low-carbohydrate diets. These diets induce greater weight loss at three and six months than traditional low-fat diets; however, by one year there is no significant difference in maintained weight loss. Weight loss is directly related to calorie content and the ability to maintain caloric restriction; the proportions of nutrients in the diet are irrelevant. Low-carbohydrate diets had lower dropout rates than low-fat diets in several studies, possibly because of the high protein content and low glycemic index, which can be appetite suppressing. Data indicate that low-carbohydrate diets are a safe, reasonable alternative to low-fat diets for weight loss. Additional studies are needed to investigate the long-term safety and effectiveness of these and other approaches to weight loss. (+info)