Post-exercise substrate utilization after a high glucose vs. high fructose meal during negative energy balance in the obese

OBJECTIVE: To assess the effects of negative energy balance on the metabolic response of a meal containing either glucose or fructose as the primary source of carbohydrate after exercise in obese individuals in energy balance, or negative energy balance. RESEARCH METHODS AND PROCEDURES: Fourteen adults with mean body mass index (BMI) 30.3 +/- 1 kg/m2, age 26 +/- 2 years, and weight 93.5 +/- 5.4 kg, adhered to an energy-balanced (EB) or a negative energy-balanced (NEB) diet for 6 days. On Day 7, subjects exercised at 70% VO2peak for 40 minutes then consumed either high glucose (50 g of glucose, HG) or high fructose (50 g of fructose, HF) liquid meal. Substrate utilization was measured by indirect calorimetry for 3 hours. Blood samples were collected before exercise and 0, 30, 60, 120, and 180 minutes after consuming the meal. RESULTS: The HG produced 15.9% greater glycemic (p < 0.05) and 30.9% larger insulinemic (p < 0.05) responses than the HF under both EB and NEB conditions. After the NEB diet, carbohydrate and fat oxidation did not differ for HG and HF. In contrast, carbohydrate oxidation increased 31%, and fat oxidation decreased 39% with HF compared with HG after the EB diet. Thus, HF and HG consumed after exercise produced marked differences in macronutrient oxidation when obese subjects followed an EB diet, but no difference when adhering to a NEB diet. DISCUSSION: The data suggest that the use of fructose in supplements/meals may provide no additional benefit in terms of substrate utilization during a weight loss program involving diet and exercise.     

High rates of exogenous carbohydrate oxidation from a mixture of glucose and fructose ingested during prolonged cycling exercise

A recent study from our laboratory has shown that a mixture of glucose and fructose ingested at a rate of 1.8 g/min leads to peak oxidation rates of approximately 1.3 g/min and results in approximately 55% higher exogenous carbohydrate (CHO) oxidation rates compared with the ingestion of an isocaloric amount of glucose. The aim of the present study was to investigate whether a mixture of glucose and fructose when ingested at a high rate (2.4 g/min) would lead to even higher exogenous CHO oxidation rates (>1.3 g/min). Eight trained male cyclists (VO2max: 68+/-1 ml/kg per min) cycled on three different occasions for 150 min at 50% of maximal power output (60+/-1% VO2max) and consumed either water (WAT) or a CHO solution providing 1.2 g/min glucose (GLU) or 1.2 g/min glucose+1.2 g/min fructose (GLU+FRUC). Peak exogenous CHO oxidation rates were higher (P<0.01) in the GLU+FRUC trial compared with the GLU trial (1.75 (SE 0.11) and 1.06 (SE 0.05) g/min, respectively). Furthermore, exogenous CHO oxidation rates during the last 90 min of exercise were approximately 50% higher (P<0.05) in GLU+FRUC compared with GLU (1.49 (SE 0.08) and 0.99 (SE 0.06) g/min, respectively). The results demonstrate that when a mixture of glucose and fructose is ingested at high rates (2.4 g/min) during 150 min of cycling exercise, exogenous CHO oxidation rates reach peak values of approximately 1.75 g/min.     

Comparison of extracellular and net glucose oxidation measured isotopically and by indirect calorimetry during high and low glucose turnover

To determine the extent to which glucose oxidation measured by indirect calorimetry reflects glucose oxidation measured isotopically, subjects were studied during a 6-h hyperinsulinemic euglycemic clamp (1 mU.kg-1.min-1) and during infusion of saline. [6-14C]glucose was infused on both occasions. Breath was collected for determination of the specific activity of carbon dioxide, oxygen consumption, and carbon dioxide production. Glucose turnover during hyperinsulinemia was approximately eightfold higher than during saline infusion. During the final 1.5 h of the hyperinsulinemic glucose clamp, oxidation measured isotopically remained slightly but consistently lower (P less than 0.05) than that measured by indirect calorimetry (13.8 +/- 1.1 vs 16.5 +/- 1.7 mumol.kg-1.min-1, respectively). In contrast, during the saline infusion, glucose oxidation measured isotopically did not differ from that measured by indirect calorimetry (8.3 +/- 0.6 vs 7.2 +/- 2.8 mumol.kg-1.min-1, respectively). We conclude that although net glucose oxidation measured isotopically was slightly lower than that measured by indirect calorimetry, both techniques provide similar estimates of glucose oxidation over a wide range of glucose disposal.     

The effects of ingesting polylactate or glucose polymer drinks during prolonged exercise.

Five trained, fasted male cyclists rode a cycle ergometer three times at 50% of VO2max for 180 min. Using a balanced order, double-blind procedure, subjects were given either a solution containing polylactate (PL: 80% polylactate, 20% sodium lactate, in 7% solution with water), glucose polymer (GP: multidextrin in 7% solution with water), or control (C: water sweetened with aspartame) 5 min before exercise and at 20-min intervals during exercise. Venous blood samples were taken at rest and at 20-min intervals during exercise. In general, PL and GP rendered similar results except that pH and bicarbonate (HCO3-) were higher in PL. There were no differences between treatments in perceived exertion, sodium, potassium, chloride, lactate, heart rate, oxygen consumption, rectal temperature, or selected skin temperatures. These data show that polylactate may help maintain blood glucose and enhance blood buffering capacity during prolonged exercise and could be a useful component in an athletic fluid replacement beverage.     

Screening for gestational diabetes mellitus: comparison of a glucose polymer and a glucose monomer test beverage.

BACKGROUND: The current test for gestational diabetes mellitus (GDM) uses a glucose monomer test beverage, which frequently causes gastrointestinal symptoms, and venipuncture. We investigated a simplified test using a beverage of glucose polymer and a capillary whole blood glucose measurement. METHODS: In a randomized, double-blind clinical trial, women at 24 to 28 weeks' gestation received a 50-g glucose monomer (n = 41) or glucose polymer (n = 35) beverage. Venous and capillary blood samples were obtained 1 hour later. The women then completed standardized questionnaires about their symptoms. RESULTS: The glucose polymer beverage was associated with significantly fewer symptoms than was the glucose monomer drink: the mean was 1.1 symptoms per test with the glucose monomer drink and 0.4 symptoms per test with the glucose polymer drink (P less than 0.05), 51 percent of the women developed symptoms after drinking the glucose monomer beverage, and 27 percent of the women developed symptoms after drinking the glucose polymer beverage (P less than 0.05). Glucose type did not affect the 1-hour plasma glucose level, mean 5.94 mmol/L (107 mg/dL) for the glucose monomer and 5.76 mmol/L (103.8 mg/dL) for the glucose polymer (P = 0.79). For the capillary test, sensitivity was 0.75 and specificity was 0.82 in detecting a screening test positive by the venous plasma glucose criterion. CONCLUSION: The results of this study indicate that a glucose polymer beverage is better tolerated than a glucose monomer beverage during GDM screening, but capillary glucose measurement might be of limited use in clinics where many personnel perform the capillary blood glucose testing.     

Different effects of long-chain and medium-chain triglycerides on glucose oxidation during total parenteral nutrition.

This study was undertaken to clarify differences in the effects of lipid emulsions containing either long-chain or medium-chain triglycerides (MCT) on glucose metabolism during total parenteral nutrition (TPN). Glucose kinetics were assessed in beagle dogs using primed, constant infusions of [14C]- and [6-3H]glucose. The rate of appearance of glucose, the percent of VCO2 derived from the oxidation of glucose, the rate of glucose oxidation, and the percent of glucose uptake oxidized were measured at the end of 72 hours of each of the two TPN regimens, ie, TPN in which soybean oil served as long-chain triglyceride comprising 40% of nonprotein calories (L-TPN), and TPN in which tricaprylin emulsion served as MCT (M-TPN). Glucose intake was 5.9 +/- 0.5 mg/kg per minute in L-TPN and 5.8 +/- 0.2 mg/kg per minute in M-TPN. There was no significant difference in the rate of glucose appearance between L-TPN and M-TPN. The rate of glucose oxidation was higher with M-TPN than with L-TPN (p < .05). Not only the percent of VCO2 derived from the oxidation of glucose but also the percent of glucose uptake oxidized tended to be higher during M-TPN than during L-TPN. These findings suggest that the glucose metabolism of dogs receiving L-TPN is different from that of dogs receiving M-TPN.     

Eating self-efficacy and weight cycling: a prospective clinical study

Previous retrospective studies have not identified global psychosocial consequences of weight cycling. These lack of findings may be due to limitations associated with retrospective research or with using general psychological measures rather than weight-specific measures. This prospective study examined changes in a weight-specific measure, eating self-efficacy, using an obese clinical population who returned to a multidisciplinary weight management program subsequent to weight regain. Subjects did not demonstrate any change in eating self-efficacy despite experiencing weight loss and then weight regain. Individuals returning for treatment may be a select population, thus suggesting that there may not be negative psychological effects of weight cycling for all individuals. Implications for further research are discussed.     

Effects of dietary restraint vs exercise during weight maintenance in obese men

OBJECTIVE: To investigate the effect of dietary restraint with or without exercise during weight maintenance after energy restriction. SUBJECTS AND METHODS: In total, 40 obese male subjects (mean BMI 32.3 kg/m(2); mean age 39 y) were recruited and randomly divided into a diet (D; n=20) and a diet plus exercise (DE; n=20) group. Both groups participated in an energy restriction programme (ER), which was followed by a weight maintenance phase (WM). Subjects in the DE also participated in an exercise programme. Body mass (BM) and the scores on the three factor eating questionnaire (TFEQ) were measured before and after the ER and after WM. RESULTS: No significant differences between both groups were found. All data taken together showed that BM loss during ER was explained by initial BM (r(2)=0.3, P<0.0005) and inversely by initial cognitive restraint (F1) (r(2)=0.4, P<0.0005) in a stepwise regression. BM regain during WM was explained by BM loss (r(2)=0.5, P<0.001) and by increase in F1 during ER (r(2)=0.6, P<0.001), while the exercise intervention did not contribute further to the explained variation. Subjects with a relatively high diet frequency prior to the study had relatively significant higher initial F1 scores (P<0.05). During ER, increase in F1 was associated with decrease in general hunger (F3). CONCLUSION: Successful BM loss was associated with higher initial BM and lower initial F1. Successful WM was explained by BM loss and increase in F1 during ER, irrespective of possible exercise training effects. Successful WM was reduced when F1 scores reach their limit, due to diet-frequency.     

Thinness expectations and weight cycling in a sample of middle-aged adults

BackgroundThe False Hope Syndrome suggests that unrealistic expectations of dieting and weight loss are key constructs in the prediction of behavioral failure and may exacerbate weight cycling. The objective of this study was to determine cross-sectional associations among dieting and thinness expectations and weight cycling history within the framework of the False Hope Syndrome.MethodsParticipants were middle-aged (45 ± 12 years) women (n = 116) and men (n = 98) recruited via worksite intranet distributions. Information on dieting and thinness expectations, weight loss attempts, and weight cycling history was gathered using standard questionnaires.ResultsMore women than men reported currently dieting (43% vs. 26%; p < 0.01). Moderate [OR = 2.54; 95%CI: 1.01–6.45] and higher [OR = 2.70; 95%CI: 1.07–6.80] levels of the thinness expectation score were significantly associated with the greater odds of weight cycling, independent of age, sex, BMI, and weight loss attempts.ConclusionsThese data are the first to extend the pervasive and potent influence of thinness expectancy to middle-aged persons and in particular, to men.     

Effects of high carbohydrate, high fat, or high protein diets on glucose oxidation by isolated intestinal epithelial cells of the chick.

A parallel study of 3-O-methyl glucose transport by everted intestinal sacs and [U-14C]glucose oxidation by isolated, dispersed intestinal cells was done in chicks (1) adapted to a high carbohydrate (HC), high fat (HF), or high protein (HP) diet for 2 weeks or (2) fasted up to 5 days. HF and HP diets significantly decreased both serosal : mucosal (S : M) distribution ratios of 3-O-methyl glucose by everted sacs and glucose oxidation by dispersed cells. The effects were more pronounced in HF diet-fed chicks. Fasting signficiantly increased the S : M ratio throughout a 5-day fasting period, whereas glucose oxidation was increased after a 1-day fast and was decreased after a 5-day fast. Feeding HC diet for 1 week to chicks adapted to HF diet restored both functions to control levels. Refeeding fasted chicks for 3 days also restored S : M ratio to control levels. Histological examination of tissues from various treatment groups revealed no obvious morphological differences. The results suggest that the functional changes described represent adaptive changes at the cellular level and that these changes are readily reversible.     

Satiety related to 24 h diet-induced thermogenesis during high protein/carbohydrate vs high fat diets measured in a respiration chamber.

OBJECTIVE: Assessment of a possible relationship between perception of satiety and diet-induced thermogenesis, with different macronutrient compositions, in a controlled situation over 24 h. DESIGN: Two diets with different macronutrient compositions were offered to all subjects in randomized order. SETTING: The study was executed in the respiration chambers at the department of Human Biology, Maastricht University. SUBJECTS: Subjects were eight females, ages 23-33 y, BMI 23+/-3 kg/m2, recruited from University staff and students. INTERVENTIONS: Subjects were fed in energy balance, with protein/carbohydrate/fat: 29/61/10 and 9/30/61 percentage of energy, with fixed meal sizes and meal intervals, and a fixed activity protocol, during 36 h experiments in a respiration chamber. The appetite profile was assessed by questionnaires during the day and during meals. Diet induced thermogenesis was determined as part of the energy expenditure. RESULTS: Energy balance was almost complete, with non-significant deviations. Diet-Induced-Thermogenesis (DIT) was 14.6+/-2.9%, on the high protein/carbohydrate diet, and 10.5+/-3.8% on the high fat diet (P < 0.01). With the high protein/high carbohydrate diet, satiety was higher during meals (P < 0.001; P < 0.05), as well as over 24 h (P < 0.001), than with the high fat diet. Within one diet, 24 h DIT and satiety were correlated (r = 0.6; P < 0.05). The difference in DIT between the diets correlated with the differences in satiety (r = 0.8; P < 0.01). CONCLUSION: In lean women, satiety and DIT were synchronously higher with a high protein/high carbohydrate diet than with a high fat diet. Differences (due to the different macronutrient compositions) in DIT correlated with differences in satiety over 24 h.     

Low molecular weight heparin in the symptomatic treatment of chronic venous insufficiency. Controlled double blind study vs calcium heparin

Ninety patients suffering from chronic venous insufficiency were submitted to subcutaneous treatment with calcium heparin in fixed doses (5000 I.U. t.i.d.) or with different doses of a low molecular weight heparin fraction 7,500 AXaU/day or 15,000 AXaU/day) for thirty days with a double blind random design. On days 0, 15 and 30, clinical parameters were assessed (edema, painfulness, cutaneous trophic lesions, paresthesia) and laboratory tests carried out (fibrinogenemia, plasma viscosity, euglobin lysis time, general tolerance parameters); at the beginning and at the end of the study the plethysmographic indexes of maximum venous flow and venous capacitance were evaluated. Treatment with 15,000 AXaU, of low molecular weight heparin caused modifications of the clinical and instrumental parameters which were on the whole better than those caused by heparin calcium t.i.d. throughout the study. The administration of 7,500 AXaU of low molecular weight heparin was practically equivalent to the control treatment at the end of the study, although at the intermediate assessment it was slightly less effective despite the fact that it had produced significant modifications with respect to the basal values. Treatment with low molecular weight heparin, with both doses used, produced fewer side effects than the reference drug.     

Risk factors for hypertension in obese women. The role of weight cycling

OBJECTIVE: To study significant factors associated with the risk of hypertension among obese women, with and without a history of weight cycling (WC). DESIGN: Case-control study. SETTING: Obesity Clinic of Chieti University, Italy. SUBJECTS: A group of 258 obese women aged 25-64 y (103 cases with hypertension and 155 controls) were recruited. All obese subjects had the same clinical characteristics, were without a family history for hypertension, were non-smokers, had normal lipidemic profiles and normal glucose tolerance, were not taking any medication and were otherwise healthy. INTERVENTION: In the weight cycling women, the history of WC was established on the basis of at least five weight losses in the previous 5 y due to dieting, with a weight loss of at least 4.5 kg per cycle. A logistic regression model adjusted for confounding variables such as waist-to-hip ratio (WHR) and weight cycling history parameters was used and the odds ratio (OR) with 95% confidence intervals was calculated. RESULTS: The risk of hypertension increases in subjects with larger WHR (OR 7.8; 95% CI 3.4-17.9) and with a positive history for WC (OR 4.1; 95% CI 2.4-6.9). Further, in obese patients with WC, the weight cycling index and the sum of the weight regained are also important risk factors for hypertension. CONCLUSIONS: These findings could support the hypothesis that it is the combined exposure of central-type obesity and WC that strongly raises the risk of hypertension. SPONSORSHIP: This work has been financially supported by a grant of Ministero dell'Università e della Ricerca Scientifica e Tecnologica.     

Weight cycling, weight gain, and risk of hypertension in women.

To assess prospectively the relation between body mass index, weight gain, repeated intentional weight losses, and the risk of self-reported hypertension, the authors studied 46,224 women who were participants in the Nurses Health Study II, who were free of hypertension in 1993, and who completed questions on intentional weight losses between 1989 and 1993. Women who reported they had intentionally lost > or =20 lbs (9 kg) > or =3 times were classified as severe weight cyclers. Women who had intentionally lost > or =10 lbs (4.5 kg) > or =3 times, but who did not meet the criteria for severe weight cycling, were classified as mild weight cyclers. Between 1993 and 1995, 1,107 incident cases of diagnosed hypertension were reported. Body mass index and weight gain, but not weight cycler status, were independently associated with the development of hypertension. For each 10 lb (4.5 kg) gain in weight between 1989 and 1993, the risk of hypertension increased 20% (odds ratio (OR) = 1.20, 95% confidence interval (CI) 1.15, 1.24). After adjustment for body mass index and weight gain, the risks associated with mild weight cycling (OR = 1.15, 95% CI 1.00, 1.33) and severe weight cycling (OR = 1.13, 95% CI 0.79, 1.61) were small and not significant. Thus, the results of this study offer support for the current weight guidelines and provide further evidence of the health risks associated with excessive weight and weight gain. However, these data do not suggest an independent effect of weight cycling on risk of hypertension.     

Novel configurations of high molecular weight species of the pertussis toxin vaccine component

Pertussis toxin (PT) is used in its formaldehyde-detoxified form in acellular pertussis vaccines for preventing whooping cough in children. The effects of formaldehyde treatment (up to 0.5% (w/v) formaldehyde) on the size, molecular association, folding and monoclonal antibody (mAb) binding of PT were studied to further define the structural nature of the high molecular weight species as related to their epitope integrity. Analytical ultracentrifugation (AUC) demonstrated that formaldehyde treatment of PT prevented the dissociation of the holotoxin. Together with results from size exclusion chromatography (SEC), SEC/multi-angle laser light scattering (MALLS) and immunoblotting it was demonstrated that PT increased in molecular weight and heterogeneity as a function of formaldehyde concentration, caused at least in part by covalent cross-linking. Five mAbs specific for PT subunits (S1-S5) bound to the cross-linked species, although there was some loss of epitopes in the larger aggregates. Intrinsic fluorescence spectroscopy gave evidence of progressive unfolding and re-association of PT. These findings demonstrate that a favourable balance between protein stabilisation and denaturation may be achieved by the treatment of pertussis toxin with formaldehyde, and provides a basis for determining the significance of high molecular weight cross-linked species of pertussis toxin in protection against whooping cough.     

Detection of workers sensitised to high molecular weight allergens: a diagnostic study in laboratory animal workers

Objectives: To determine whether results from questionnaires, exposure measurements, and laboratory tests, commonly used in occupational health practice, can predict the presence or absence of sensitisation in workers exposed to high molecular weight (HMW) allergens. The study aims to develop and validate a diagnostic rule to predict sensitisation in laboratory animal workers. The main reason for such research is efficiency.

Methods: Baseline data from 551 laboratory animal workers participating in an ongoing cohort study, bridging a period of 3 years, were used for diagnostic research. Data from 472 workers participating in the study during the first period were used to develop a prediction rule; these workers represented the derivation set. Data from 79 workers, participating during the second period, were used to evaluate the rule's performance—the validation set. Serum samples were analysed for specific immunoglobulin E (IgE) antibodies against common and laboratory animal allergens. Questionnaire items, exposure determinants, IgE serology, skin prick tests (SPTs), and lung function tests were analysed, corresponding to diagnostic investigation, in a multiple logistic regression model. The accuracy of the model was evaluated by receiver operating characteristic (ROC) curve analysis, and by comparison of the predicted and observed prevalences.

Results: Asthmatic symptoms, (work related) allergic symptoms, sex, occupational exposure to rats, and a positive SPT to common allergens, showed the best performance in discriminating workers at high or at low risk of being sensitised.

Conclusion: High and low risk categories for work related sensitisation can be distinguished from simple questionnaire data and SPT results. The method can easily be applied in occupational medical practice and may markedly increase the efficiency of occupational health surveillance in laboratory animal workers as well as other workers exposed to HMW allergens.

     

Muscle and plasma amino acids during semi-starvation in normal subjects: hypocaloric glucose vs. amino acid infusions

Normal subjects were fed hypocaloric amounts of amino acids or glucose for 3 days to separate the effects of these nutrients from those of trauma on muscle and plasma amino acids. Intracellular and plasma levels of Val, Leu and Ile were increased in both groups but were increased to a greater extent when amino acids were infused. Intracellular free glutamine concentration in muscle tissue was not significantly altered. Some of the trauma induced changes in amino acids can be replicated by maintaining normal subjects on hypocaloric amino acids; the decrease in glutamine concentration seen with trauma is not a function of hypocaloric nutrition.