Discrepancy between self-reported and actual caloric intake and exercise in obese subjects.

Discrepancy between self-reported and actual caloric intake and exercise in obese subjects.

Lichtman SW, Pisarska K, Berman ER, Pestone M, Dowling H, Offenbacher E, Weisel H, Heshka S, Matthews DE, Heymsfield SB.

Quote:BACKGROUND AND METHODS. Some obese subjects repeatedly fail to lose weight even though they report restricting their caloric intake to less than 1200 kcal per day. We studied two explanations for this apparent resistance to diet--low total energy expenditure and underreporting of caloric intake--in 224 consecutive obese subjects presenting for treatment. Group 1 consisted of nine women and one man with a history of diet resistance in whom we evaluated total energy expenditure and its main thermogenic components and actual energy intake for 14 days by indirect calorimetry and analysis of body composition. Group 2, subgroups of which served as controls in the various evaluations, consisted of 67 women and 13 men with no history of diet resistance. RESULTS. Total energy expenditure and resting metabolic rate in the subjects with diet resistance (group 1) were within 5 percent of the predicted values for body composition, and there was no significant difference between groups 1 and 2 in the thermic effects of food and exercise. Low energy expenditure was thus excluded as a mechanism of self-reported diet resistance. In contrast, the subjects in group 1 underreported their actual food intake by an average (+/- SD) of 47 +/- 16 percent and overreported their physical activity by 51 +/- 75 percent. Although the subjects in group 1 had no distinct psychopathologic characteristics, they perceived a genetic cause for their obesity, used thyroid medication at a high frequency, and described their eating behavior as relatively normal (all P < 0.05 as compared with group 2). CONCLUSIONS. The failure of some obese subjects to lose weight while eating a diet they report as low in calories is due to an energy intake substantially higher than reported and an overestimation of physical activity, not to an abnormality in thermogenesis.

Sodium Bicarbonate Ingestion and Boxing Performance.

Sodium Bicarbonate Ingestion and Boxing Performance.

Siegler JC, Hirscher K.

Department of Sport, Health and Exercise Science, University of Hull, Hull HU6 7RX, UK.

Siegler, JC and Hirscher, K. Sodium bicarbonate ingestion and boxing performance. J Strength Cond Res 23(4): 000-000, 2009-Boxing is a sport that consists of multiple high-intensity bouts separated by minimal recovery time and may benefit from a pre-exercise alkalotic state. The purpose of this study was to observe the ergogenic potential of sodium bicarbonate (NaHCO3) ingestion on boxing performance. Ten amateur boxers volunteered to participate in 2 competitive sparring bouts. The boxers were prematched for weight and boxing ability and consumed either 0.3 g.kg body weight (BW) of NaHCO3 (BICARB) or 0.045 g.kg BW of NaCl placebo (PLAC) mixed in diluted low calorie-flavored cordial. The sparring bouts consisted of four 3-minute rounds, each separated by 1-minute seated recovery. Blood acid-base (pH, bicarbonate [HCO3], base excess [BE]), and performance (rates of perceived exertion [RPE], heart rate [HR] [HRave and HRmax], total punches landed successfully) profiles were analyzed before (where applicable) and after sparring. The results indicated a significant interaction effect for HCO3 (p </= 0.001) and BE (p < 0.001), but not for pH (p = 0.48). Post hoc analysis revealed higher presparring HCO3 and BE for the BICARB condition, but no differences between the BICARB and PLAC conditions postsparring. There was a significant increase in punches landed during the BICARB condition (p < 0.001); however, no significant interaction effects for HRave (p = 0.15), HRmax (p = 0.32), or RPE (p = 0.38). The metabolic alkalosis induced by the NaHCO3 loading elevated before and after sparring blood buffering capacity. In practical application, the findings suggest that a standard NaHCO3 loading dose (0.3 g.kg) improves punch efficacy during 4 rounds of sparring performance.

The microbiome and obesity: is obesity linked to our gut flora?

The microbiome and obesity: is obesity linked to our gut flora?

Tsai F, Coyle WJ.

Division of Gastroenterology and Hepatology, Scripps Clinic Torrey Pines, 10666 North Torrey Pines Road, N203, La Jolla, CA 92037, USA. tsai.franklin@scrippshealth.org

The human gut is a lush microbial ecosystem containing about 100 trillion microorganisms, whose collective genome, the microbiome, contains 100-fold more genes than the entire human genome. The symbiosis of our extended genome plays a role in host homeostasis and energy extraction from diet. In this article, we summarize some of the studies that have advanced the understanding of the microbiome and its effects on metabolism, obesity, and health. Metagenomic studies demonstrated that certain mixes of gut microbiota may protect or predispose the host to obesity. Furthermore, microbiota transplantation studies in germ-free murine models showed that the efficient energy extraction traits of obese-type gut flora are transmissible. The proposed methods by which the microbiome may contribute to obesity include increasing dietary energy harvest, promoting fat deposition, and triggering systemic inflammation. Future treatments for obesity may involve modulation of gut microbiota using probiotics or prebiotics.

The effects of green tea on weight loss and weight maintenance: a meta-analysis.

The effects of green tea on weight loss and weight maintenance: a meta-analysis.

Hursel R, Viechtbauer W, Westerterp-Plantenga MS.

Department of Human Biology, Nutrition and Toxicology Research Institute Maastricht (NUTRIM) Maastricht University, Maastricht, The Netherlands.

IntroductionDifferent outcomes of the effect of green tea on weight loss (WL) and weight maintenance (WM) have been reported in studies with subjects differing in ethnicity and habitual caffeine intake.PurposeTo elucidate by meta-analysis whether green tea indeed has a function in body weight regulation.MethodsEnglish-language studies about WL and WM after green tea supplementation were identified through PubMed and based on the references from retrieved articles. Out of the 49 studies initially identified, a total of 11 articles fitted the inclusion criteria and provided useful information for the meta-analysis. Effect sizes (mean weight change in treatment versus control group) were computed and aggregated based on a random-effects model. The influence of several moderators on the effect sizes was examined.ResultsCatechins significantly decreased body weight and significantly maintained body weight after a period of WL (\[mucirc]=-1.31 kg; P<0.001). Inhibition of this effect by high habitual caffeine intake (>300 mg per day) failed to reach significance (\[mucirc]=-0.27 kg for high and \[mucirc]=-1.60 kg for low habitual caffeine intake; P=0.09). Also, the seemingly smaller effect of catechins in Caucasian (\[mucirc]=-0.82 kg) subjects compared with Asians (\[mucirc]=-1.51 kg; P=0.37) did not reach significance. Interaction of ethnicity and caffeine intake was a significant moderator (P=0.04).Conclusions Catechins or an epigallocatechin gallate (EGCG)-caffeine mixture have a small positive effect on WL and WM. The results suggest that habitual caffeine intake and ethnicity may be moderators, as they may influence the effect of catechins

Dietary Blueberry Attenuates Whole-Body Insulin Resistance in High Fat-Fed Mice by Reducing Adipocyte Death and Its Inflammatory Sequelae

Dietary Blueberry Attenuates Whole-Body Insulin Resistance in High Fat-Fed Mice by Reducing Adipocyte Death and Its Inflammatory Sequelae 

[Nutrition and Disease]

from Journal of Nutrition current issue by DeFuria, J., Bennett, G., Strissel, K. J., Perfield, J. W., Milbury, P. E., Greenberg, A. S., Obin, M. S.

Adipose tissue (AT) inflammation promotes insulin resistance (IR) and other obesity complications. AT inflammation and IR are associated with oxidative stress, adipocyte death, and the scavenging of dead adipocytes by proinflammatory CD11c+ AT macrophages (ATM). We tested the hypothesis that supplementation of an obesitogenic (high-fat) diet with whole blueberry (BB) powder protects against AT inflammation and IR. Male C57Bl/6j mice were maintained for 8 wk on 1 of 3 diets: low-fat (10% of energy) diet (LFD), high-fat (60% of energy) diet (HFD) or the HFD containing 4% (wt:wt) whole BB powder (1:1 Vaccinium ashei and V. corymbosum) (HFD+B). BB supplementation (2.7% of total energy) did not affect HFD-associated alterations in energy intake, metabolic rate, body weight, or adiposity. We observed an emerging pattern of gene expression in AT of HFD mice indicating a shift toward global upregulation of inflammatory genes (tumor necrosis factor-, interleukin-6, monocyte chemoattractant protein 1, inducible nitric oxide synthase), increased M1-polarized ATM (CD11c+), and increased oxidative stress (reduced glutathione peroxidase 3). This shift was attenuated or nonexistent in HFD+B-fed mice. Furthermore, mice fed the HFD+B were protected from IR and hyperglycemia coincident with reductions in adipocyte death. Salutary effects of BB on adipocyte physiology and ATM gene expression may reflect the ability of BB anthocyanins to alter mitogen-activated protein kinase and nuclear factor-B stress signaling pathways, which regulate cell fate and inflammatory genes. These results suggest that cytoprotective and antiinflammatory actions of dietary BB can provide metabolic benefits to combat obesity-associated pathology.

Endocannabinoids May Mediate the Ability of (n-3) Fatty Acids to Reduce Ectopic Fat and Inflammatory Mediators in Obese Zucker Rats

Endocannabinoids May Mediate the Ability of (n-3) Fatty Acids to Reduce Ectopic Fat and Inflammatory Mediators in Obese Zucker Rats 

[Nutrient Physiology, Metabolism, and Nutrient-Nutrient Interactions]

from Journal of Nutrition current issue by Batetta, B., Griinari, M., Carta, G., Murru, E., Ligresti, A., Cordeddu, L., Giordano, E., Sanna, F., Bisogno, T., Uda, S., Collu, M., Bruheim, I., Di Marzo, V., Banni, S.

Dietary (n-3) long-chain PUFA [(n-3) LCPUFA] ameliorate several metabolic risk factors for cardiovascular diseases, although the mechanisms of these beneficial effects are not fully understood. In this study, we compared the effects of dietary (n-3) LCPUFA, in the form of either fish oil (FO) or krill oil (KO) balanced for eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) content, with a control (C) diet containing no EPA and DHA and similar contents of oleic, linoleic, and -linolenic acids, on ectopic fat and inflammation in Zucker rats, a model of obesity and related metabolic dysfunction. Diets were fed for 4 wk. Given the emerging evidence for an association between elevated endocannabinoid concentrations and metabolic syndrome, we also measured tissue endocannabinoid concentrations. In (n-3) LCPUFA-supplemented rats, liver triglycerides and the peritoneal macrophage response to an inflammatory stimulus were significantly lower than in rats fed the control diet, and heart triglycerides were lower, but only in KO-fed rats. These effects were associated with a lower concentration of the endocannabinoids, anandamide and 2-arachidonoylglycerol, in the visceral adipose tissue and of anandamide in the liver and heart, which, in turn, was associated with lower levels of arachidonic acid in membrane phospholipids, but not with higher activity of endocannabinoid-degrading enzymes. Our data suggest that the beneficial effects of a diet enriched with (n-3) LCPUFA are the result of changes in membrane fatty acid composition. The reduction of substrates for inflammatory molecules and endocannabinoids may account for the dampened inflammatory response and the physiological reequilibration of body fat deposition in obese rats.

Fish-oil supplementation induces antiinflammatory gene expression profiles in human blood mononuclear cells

Fish-oil supplementation induces antiinflammatory gene expression profiles in human blood mononuclear cells 

[Gene-nutrient interactions]

from American Journal of Clinical Nutrition current issue by Bouwens, M., van de Rest, O., Dellschaft, N., Bromhaar, M. G., de Groot, L. C., Geleijnse, J. M, Muller, M., Afman, L. A

Background: Polyunsaturated fatty acids can have beneficial effects on human immune cells, such as peripheral blood mononuclear cells (PBMCs). However, the mechanisms of action of polyunsaturated fatty acids on immune cells are still largely unknown.

Objective: The objective was to examine the effects of supplementation with the polyunsaturated fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) on whole-genome PBMC gene expression profiles, in healthy Dutch elderly subjects participating in a double-blind trial, by using whole-genome transcriptomics analysis.

Design: The subjects were randomly allocated to 1 of 3 groups: 1) consumption of 1.8 g EPA+DHA/d (n = 36), 2) consumption of 0.4 g EPA+DHA/d (n = 37), or 3) consumption of 4.0 g high–oleic acid sunflower oil (HOSF)/d (n = 38). All supplements were given in capsules. Before and after 26 wk of intervention, blood samples were collected. Microarray analysis was performed on PBMC RNA from 23 subjects who received 1.8 g EPA+DHA/d and 25 subjects who received HOSF capsules. Quantitative real-time polymerase chain reaction was performed in all 111 subjects.

Results: A high EPA+DHA intake changed the expression of 1040 genes, whereas HOSF intake changed the expression of only 298 genes. EPA+DHA intake resulted in a decreased expression of genes involved in inflammatory- and atherogenic-related pathways, such as nuclear transcription factor B signaling, eicosanoid synthesis, scavenger receptor activity, adipogenesis, and hypoxia signaling.

Conclusion: These results are the first to show that intake of EPA+DHA for 26 wk can alter the gene expression profiles of PBMCs to a more antiinflammatory and antiatherogenic status. This trial was registered at clinicaltrials.gov as NCT00124852.

Relations between protein intake and blood pressure in Japanese men and women: the Circulatory Risk in Communities Study (CIRCS)

Relations between protein intake and blood pressure in Japanese men and women: the Circulatory Risk in Communities Study (CIRCS) 

[Nutritional epidemiology and public health]

from American Journal of Clinical Nutrition current issue by Umesawa, M., Sato, S., Imano, H., Kitamura, A., Shimamoto, T., Yamagishi, K., Tanigawa, T., Iso, H.

Background: An inverse association between protein intake and blood pressure has been reported in Western countries. However, the evidence is limited for Asians, whose protein sources are different from those in Western populations.

Objectives: The objective was to examine the association between protein intake and blood pressure in Japanese adults.

Methods: We conducted a population-based, cross-sectional study of 7585 subjects (3499 men and 4086 women) from 40 to 69 y of age living in 5 communities in Japan. Dietary intakes of total, animal, and plant protein were estimated by a single 24-h dietary recall. We then examined the associations between dietary intake of those proteins and blood pressure after adjustment for age, sex, community, body mass index, antihypertensive medication use, ethanol intake, smoking, and dietary intakes of sodium, potassium, and calcium.

Results: After adjustment for cardiovascular disease risk factors, a 25.5-g/d increment in total protein intake was associated with a decrease in systolic blood pressure of 1.14 mm Hg (P < 0.001) and in diastolic blood pressure of 0.65 mm Hg (P < 0.001), and a 19.9-g/d increment in animal protein intake was associated with a decrease in systolic blood pressure of 1.09 mm Hg (P < 0.001) and in diastolic blood pressure of 0.41 mm Hg (P = 0.003). A 13.1-g/dincrement in plant protein intake was associated with a decrease in diastolic blood pressure of 0.57 mm Hg (P < 0.001). Further adjustment for nutritional factors weakened these associations, but the inverse associations of total protein intake with diastolic blood pressure and of animal protein intake with systolic blood pressure remained statistically significant.

Conclusion: Total and animal protein intakes were inversely associated with blood pressure in Japanese adults.

Dietary zinc restriction and repletion affects DNA integrity in healthy men

Dietary zinc restriction and repletion affects DNA integrity in healthy men 

[Vitamins, minerals, and phytochemicals]

from American Journal of Clinical Nutrition current issue by Song, Y., Chung, C. S, Bruno, R. S, Traber, M. G, Brown, K. H, King, J. C, Ho, E.

Background: Zinc plays an important role in antioxidant defense and the maintenance of cellular DNA integrity. However, no experimental human studies have been performed to examine the role of zinc status on DNA damage.

Objective: We evaluated the effects of dietary zinc depletion and repletion on DNA strand breaks, oxidative stress, and antioxidant defenses in healthy men.

Design: Nine healthy men with reported mean daily zinc intakes >11 mg/d were recruited. Subjects completed 3 consecutive dietary periods: baseline (days 1 to 13; 11 mg Zn/d), zinc depletion (days 14 to 55; 0.6 mg Zn/d for 1 wk and 4 mg Zn/d for 5 wk), and zinc repletion (days 56 to 83; 11 mg Zn/d for 4 wk with 20 mg supplemental Zn for first 7 d). Blood samples were collected on days 1, 13, 35, 55, and 83. DNA damage in peripheral blood cells, plasma oxidative stress, and antioxidant defense biomarkers were assessed.

Results: Dietary zinc depletion (6 wk) was associated with increased DNA strand breaks in peripheral blood cells (day 13 compared with day 55; P < 0.05), changes that were ameliorated by zinc repletion (day 55 compared with day 83; P < 0.05). Plasma zinc concentrations were negatively correlated with DNA strand breaks (r = –0.60, P = 0.006) during the zinc-depletion period. Plasma - and -tocopherol concentrations, plasma total antioxidant capacity, and erythrocyte superoxide dismutase activity did not change significantly, and plasma F2-isoprostanes were unaffected by dietary period.

Conclusions: Changes in dietary zinc intake affected DNA single-strand breaks. Zinc appears to be a critical factor for maintaining DNA integrity in humans.

Meta-analysis of the effects of flaxseed interventions on blood lipids

Meta-analysis of the effects of flaxseed interventions on blood lipids 

[Cardiovascular disease risk]

from American Journal of Clinical Nutrition current issue by Pan, A., Yu, D., Demark-Wahnefried, W., Franco, O. H, Lin, X.

Background: Several clinical trials have investigated the effects of flaxseed and flaxseed-derived products (flaxseed oil or lignans) on blood lipids; however, the findings have been inconsistent.

Objective: We aimed to identify and quantify the effectiveness of flaxseed and its derivatives on blood lipid profiles.

Design: A comprehensive literature search was performed on the basis of English reports of randomized controlled trials of flaxseed or its derivatives on lipid profiles in adults, which were published from January 1990 to October 2008. Attempts also were made to access unpublished data. Study quality was assessed by using the Jadad score, and a meta-analysis was conducted.

Results: Twenty-eight studies were included. Flaxseed interventions reduced total and LDL cholesterol by 0.10 mmol/L (95% CI: –0.20, 0.00 mmol/L) and 0.08 mmol/L (95% CI: –0.16, 0.00 mmol/L), respectively; significant reductions were observed with whole flaxseed (–0.21 and –0.16 mmol/L, respectively) and lignan (–0.28 and –0.16 mmol/L, respectively) supplements but not with flaxseed oil. The cholesterol-lowering effects were more apparent in females (particularly postmenopausal women), individuals with high initial cholesterol concentrations, and studies with higher Jadad scores. No significant changes were found in the concentrations of HDL cholesterol and triglycerides.

Conclusions: Flaxseed significantly reduced circulating total and LDL-cholesterol concentrations, but the changes were dependent on the type of intervention, sex, and initial lipid profiles of the subjects. Further studies are needed to determine the efficiency of flaxseed on lipid profiles in men and premenopausal women and to explore its potential benefits on other cardiometabolic risk factors and prevention of cardiovascular disease.

Effect of bite size and oral processing time of a semisolid food on satiation

Effect of bite size and oral processing time of a semisolid food on satiation 

[Obesity and eating disorders]

from American Journal of Clinical Nutrition current issue by Zijlstra, N., de Wijk, R., Mars, M., Stafleu, A., de Graaf, C.

Background: Food texture plays an important role in food intake regulation. In previous studies we showed a clear effect of viscosity on ad libitum food intake and found indications that eating rate, bite size, and oral processing time (OPT) could play a role.

Objective: The objective was to determine the effect of bite size and OPT of a food on satiation, defined as ad libitum food intake.

Design: Twenty-two healthy subjects participated in all 7 test conditions. Bite sizes were free or fixed to small bite sizes (5 g) or large bite sizes (15 g). OPT was free (only in combination with free bite size) or fixed to 3 or 9 s. Subjects consumed chocolate custard through a tube, which was connected to a peristaltic pump. Sound signals indicated OPT duration.

Results: Subjects consumed significantly more when bite sizes were large than when they were small (bite size effect: P < 0.0001) and when OPT was 3 s rather than 9 s (OPT effect: P = 0.008). Under small bite size conditions, mean (±SD) ad libitum intakes were 382 ± 197 g (3-s OPT) and 313 ± 170 g (9-s OPT). Under large bite size conditions, ad libitum intakes were much higher: 476 ± 176 g (3-s OPT) and 432 ± 163 g (9-s OPT). Intakes during the free bite size conditions were 462 ± 211 g (free OPT), 455 ± 197 g (3-s OPT), and 443 ± 202 g (9-s OPT).

Conclusion: This study shows that greater oral sensory exposure to a product, by eating with small bite sizes rather than with large bite sizes and increasing OPT, significantly decreases food intake.

Time-divided ingestion pattern of casein-based protein supplement stimulates an increase in fat-free body mass during resistance training in young untrained men

Time-divided ingestion pattern of casein-based protein supplement stimulates an increase in fat-free body mass during resistance training in young untrained men

from Nutrition Research by Andres Burk, Saima Timpmann, Luule Medijainen, Mare Vähi, Vahur Ööpik

Abstract: We hypothesized that during prolonged resistance training, time-divided ingestion pattern of casein-based protein supplement is of superior efficiency in comparison with the ingestion of the same supplement immediately before each training session. In a crossover study, 13 men aged 18 to 19 years were evaluated during 2 well-controlled, 8-week training and supplementation periods. In the time-focused supplementation regimen (TFR), the subjects consumed the supplement in the morning and in the afternoon, immediately before the training session. Time-divided supplementation regimen (TDR) included 1 morning dose, whereas the second dose was ingested in the evening, 5 hours after training. The daily dose of the supplement contained approximately 70 g of protein (82% casein) and less than 1 g of carbohydrate and fat. Body mass, body composition (dual-energy x-ray absorptiometry scanned), and one-repetition maximum (1RM) for bench press and squat were determined at the beginning and at the end of both 8-week training and supplementation periods. Training produced a significant increase in 1RM strength both in the bench press (9.4% and 7.2%) and the squat exercise (10.7% and 17.8%) in the TFR and TDR, respectively, with no differences between the supplementation regimens. Fat-free mass increased from 62.4 ± 1.2 to 63.5 ± 1.3 kg (P = .046) with TDR, whereas no change was evident with TFR. The increase in 1RM strength in the squat exercise was related to the increase in fat-free mass in TDR (r = 0.569; P = .041). These findings may have practical implications for the timing of ingestion of protein supplements to enhance the efficacy of resistance training.

Consumption of the slow-digesting waxy maize starch leads to blunted plasma glucose and insulin response but does not influence energy expenditure or appetite in humans

Consumption of the slow-digesting waxy maize starch leads to blunted plasma glucose and insulin response but does not influence energy expenditure or appetite in humans

from Nutrition Research by Amanda L. Sands, Heather J. Leidy, Bruce R. Hamaker, Paul Maguire, Wayne W. Campbell

Abstract: Limited research in humans suggests that slowly digestible starch may blunt the postprandial increase and subsequent decline of plasma glucose and insulin concentrations, leading to prolonged energy availability and satiety, compared to more rapidly digestible starch. This study examined the postprandial metabolic and appetitive responses of waxy maize starch (WM), a slow-digestible starch. It was hypothesized that the waxy maize treatment would result in a blunted and more sustained glucose and insulin response, as well as energy expenditure and appetitive responses. Twelve subjects (6 men and 6 women) (age, 23 ± 1 years; body mass index, 22.2 ± 0.7 kg/m2; insulin sensitivity [homeostatic model assessment], 16% ± 2%; physical activity, 556 ± 120 min/wk) consumed, on separate days, 50 g of available carbohydrate as WM, a maltodextrin-sucrose mixture (MS), or white bread (control). Postprandial plasma glucose and insulin, energy expenditure, and appetite (hunger, fullness, desire to eat) were measured over 4 hours. Compared to control, the 4-hour glucose response was not different for MS and WM, and the 4-hour insulin response was higher for MS (P < .005) and lower for WM (P < .05). Compared to MS, WM led to lower 4-hour glucose and insulin responses (P < .001). These differences were driven by blunted glucose and insulin responses during the first hour for WM. Postprandial energy expenditure and appetite were not different among treatments. These results support that WM provides sustained glucose availability in young, insulin-sensitive adults.

Effects of exercise training on subcutaneous and visceral adipose tissue in normal- and high-fat diet-fed rats

Effects of exercise training on subcutaneous and visceral adipose tissue in normal- and high-fat diet-fed rats

from AJP: Endocrinology and Metabolism current issue by Gollisch, K. S. C., Brandauer, J., Jessen, N., Toyoda, T., Nayer, A., Hirshman, M. F., Goodyear, L. J.

Regular physical activity improves glucose tolerance and decreases adiposity. Our aim was to investigate the effects of exercise training on subcutaneous (inguinal) and visceral (parametrial) adipose tissue in rats that were fed a chow diet (13% fat) or made insulin resistant by a high-fat diet (60% fat). Sprague-Dawley rats performed 4 wk of voluntary wheel running or were kept as sedentary controls. The training groups fed chow and the high-fat diet achieved similar running distances (8.8 ± 1.8 and 9.3 ± 1.9 km/day, respectively). Training improved oral glucose tolerance in chow-fed rats and prevented the glucose intolerance that occurred in sedentary rats fed the high-fat diet. In both subcutaneous and visceral adipose tissue, the high-fat diet-induced increases in fat pad weight (67% and 133%, respectively), adipocyte size (20% and 43%), and cell number (36% and 65%) were completely prevented by exercise training. Cytokine mRNA expression in visceral fat did not change with exercise training. However, in subcutaneous fat, training actually increased mRNA expression of several cytokines [IL-6: 80% (P < 0.05); TNF-: 100% (P < 0.05); IL-1 receptor antagonist (IL-1Ra): 57% (P = 0.08)] with no detectable increases in serum cytokine concentrations. In summary, exercise training can overcome high-fat diet-induced impairments in glucose tolerance and increases in adipocyte size, cell number, and fat pad mass. Improved glucose tolerance was accompanied by an increase in cytokine gene expression in subcutaneous fat. This finding raises the possibility of a specific role of subcutaneous adipose tissue in adaptive responses to exercise training.

Postprandial walking is better for lowering the glycemic effect of dinner than pre-dinner exercise in type 2 diabetic individuals.

Postprandial walking is better for lowering the glycemic effect of dinner than pre-dinner exercise in type 2 diabetic individuals.

Colberg SR, Zarrabi L, Bennington L, Nakave A, Thomas Somma C, Swain DP, Sechrist SR.

Old Dominion University, Norfolk, VA 23529, USA. scolberg@odu.edu

OBJECTIVES: In prior studies of exercise done before or after breakfast and lunch, postprandial activity generally reduces glycemia more than pre-meal. This study sought to examine the effects of exercise before or after an evening meal. DESIGN: Examined the differing effects of a single bout of pre- or postprandial moderate exercise or no exercise on the glycemic response to an evening (dinner) meal in individuals with type 2 diabetes. SETTING: Community-dwelling participants tested at a research university in Virginia. PARTICIPANTS: Twelve men and women subjects (mean age of 61.4+/-2.7 years) with type 2 diabetes treated with diet and/or oral medications. INTERVENTION: Three trials conducted on separate days consisting of a rest day when subjects consumed a standardized dinner with a moderate glycemic effect and 2 exercise days when they undertook 20 minutes of self-paced treadmill walking immediately before or 15 to 20 minutes after eating. MEASUREMENTS: Blood samples taken every 30 minutes over a 4-hour period and later assayed for plasma glucose; from these data both absolute and relative changes in glucose levels were determined, as well as the total glucose area under the curve (AUC) of the 4-hour testing period. Initial samples were additionally assayed for glycated hemoglobin and lipid levels. RESULTS: Twenty minutes of self-paced walking done shortly after meal consumption resulted in lower plasma glucose levels at the end of exercise compared to values at the same time point when subjects had walked pre-dinner. Total glucose AUC over 4-hours was not significantly different among trials. CONCLUSION: Postprandial walking may be more effective at lowering the glycemic impact of the evening meal in individuals with type 2 diabetes compared with pre-meal or no exercise and may be an effective means to blunt postprandial glycemic excursions.

Taurine supplementation increases skeletal muscle force production and protects muscle function during and after high-frequency in vitro stimulation

Taurine supplementation increases skeletal muscle force production and protects muscle function during and after high-frequency in vitro stimulation

from Journal of Applied Physiology recent issues by Goodman, C. A., Horvath, D., Stathis, C., Mori, T., Croft, K., Murphy, R. M., Hayes, A.

Recent studies report that depletion and repletion of muscle taurine (Tau) to endogenous levels affects skeletal muscle contractility in vitro. In this study, muscle Tau content was raised above endogenous levels by supplementing male Sprague-Dawley rats with 2.5% (wt/vol) Tau in drinking water for 2 wk, after which extensor digitorum longus (EDL) muscles were examined for in vitro contractile properties, fatigue resistance, and recovery from fatigue after two different high-frequency stimulation bouts. Tau supplementation increased muscle Tau content by ~40% and isometric twitch force by 19%, shifted the force-frequency relationship upward and to the left, increased specific force by 4.2%, and increased muscle calsequestrin protein content by 49%. Force at the end of a 10-s (100 Hz) continuous tetanic stimulation was 6% greater than controls, while force at the end of the 3-min intermittent high-frequency stimulation bout was significantly higher than controls, with a 12% greater area under the force curve. For 1 h after the 10-s continuous stimulation, tetanic force in Tau-supplemented muscles remained relatively stable while control muscle force gradually deteriorated. After the 3-min intermittent bout, tetanic force continued to slowly recover over the next 1 h, while control muscle force again began to decline. Tau supplementation attenuated F2-isoprostane production (a sensitive indicator of reactive oxygen species-induced lipid peroxidation) during the 3-min intermittent stimulation bout. Finally, Tau transporter protein expression was not altered by the Tau supplementation. Our results demonstrate that raising Tau content above endogenous levels increases twitch and subtetanic and specific force in rat fast-twitch skeletal muscle. Also, we demonstrate that raising Tau protects muscle function during high-frequency in vitro stimulation and the ensuing recovery period and helps reduce oxidative stress during prolonged stimulation.