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G Livesey

Publications and source records attributed to G Livesey.

At least 37 records · Page 2Linked to original sources
PubMed1994

Energy balance and expenditure while consuming guar gum at various fat intakes and ambient temperatures.

We devised a new model to evaluate whether dietary composition affects whole-body energy metabolism in rats. Dietary guar gum, but not corn starch, elevates both fecal energy excretion and energy expenditure. Neither ambient temperature (21 vs 28 degrees C) nor fat content of the basal diet (15% vs 33% metabolizable energy) has a marked effect on guar gum's thermogenic stimulus. Starch and guar gum each contribute 17.5 kJ/g to gross energy intake. This energy is fully available from the starch but guar gum contributes only 9-13 kJ/g to digestible energy intake on the low-fat diet (15% of energy), only 6 kJ/g to digestible energy on the higher-fat diet (33% of energy) (because of a fat-gum interaction), decreases urinary energy loss by 1.4-2.7 kJ/g gum, and elevates energy expenditure by 11.6-14.8 kJ/g. The thermogenic effect of the guar gum is highly reproducible. Several potential mechanisms to explain such elevated energy expenditure are considered. The model used to quantify the thermogenic stimulus is highly sensitive and could be applied to the trial of potentially thermogenic drugs as well as dietary ingredients.

Animals↗
PubMed1993

'Determination' of sugar alcohol and Polydextrose absorption in humans by the breath hydrogen (H2) technique: the stoichiometry of hydrogen production and the interaction between carbohydrates assessed in vivo and in vitro.

The production of hydrogen from substrates and substrate mixture of sugar alcohols and Polydextrose was determined, both in vivo using the breath hydrogen test, and in vitro, using human faecal microorganisms in anaerobic culture. One objective was to test a previous assumption that the stoichiometry of hydrogen production from different alternative carbohydrates is similar. Another objective was to discover whether hydrogen responses from mixtures of substrates were simply additive, or whether interactions occurred. The breath tests were performed in a 10 subject x 10 substrate factorial design with substrates and substrate mixtures (5-11 g) administered in 42 g chocolate confectionery. Incorporation of the alternative carbohydrates lactitol (L), Isomalt (I) and Polydextrose (P) into otherwise conventional confectionery increased breath hydrogen production by approximately 112, 73 and 11%/g respectively. There was no interaction between L and I or between P and I, but a combination of L and P approximately doubled the breath hydrogen anticipated from their individual contributions (P < 0.05). Anaerobic cultures showed a sixfold range in the efficiency of converting individual substrates and mixtures to hydrogen gas (0.003-0.018 kJ H2 per kJ carbohydrate). The positive interaction between L and P, and the lack of interaction between L and I, and between P and I, found in vivo were reproduced in vitro. The work showed that interpretation of the hydrogen breath test is confounded by differing stoichiometries for hydrogen production, by interaction between substrates and by an uncertain extent to which small intestinal hydrolysis yielding species with a fermentation stoichiometry that differs from the parent substrate.

Absorption↗
PubMed1991

Energy values and energy balance in rats fed on supplements of guar gum or cellulose.

In five experiments where guar gum (GG) or Solka-floc cellulose (SF) supplemented a semi-synthetic diet (100 g/kg) for male Wistar rats at 21 degrees, it was found that GG acutely depressed both ad lib. and meal-fed food intakes by 40-50%. The effect was temporary, with the GG having no effects on food intake in the longer term. Dietary energy balance over 28 d with animals fed on equal amounts of a basal ration showed partial digestible energy values, calculated from the intake and faecal loss of energy, for the supplements which averaged 0 kJ/g SF and 10 kJ/g GG, so that GG contributed substantial amounts of absorbable energy. Despite this additional energy from GG, there was very often no additional gain of body fat. Rather, in some experiments, fat deposition was actually decreased by supplementation with GG. GG is inferred to have a putative thermogenic effect which is often greater than the energy it supplies. This effect occurred to a greater extent in circumstances associated with a higher 'energy status', indicated by higher efficiencies of conversion of gross dietary energy to retained body energy, higher fat:lean tissue deposition ratios and the occurrence of larger deposits at the epididymal fat pad site. There was some evidence that deposition at this site was more extensively affected by GG than deposition of fat in the body as a whole. Possible implications of the present findings are discussed.

Animals↗
PubMed1991

Influence of mild cold on the components of 24 hour thermogenesis in rats.

1. The influence of two weeks' acclimation to either 28 degrees C (thermal neutrality) or 21 degrees C (mild cold) on 24 h heat production and motor activity has been investigated in male Wistar rats. Food intake was controlled and provided as a single meal of approximately 170 kJ per day. Mathematical modelling was used to relate metabolic rate to measured movement and time of day. 2. For animals at thermal neutrality it was clear that metabolic rate increased during periods of substantial measured movement and returned to baseline during periods of minimal activity. Total heat production could therefore be divided into two components: underlying and movement-induced thermogenesis. 3. At 21 degrees C, a more complex model was needed. During periods of substantial activity, the relation between metabolic rate and movement was similar to that at 28 degrees C and total heat production could be divided into the same two components of underlying and movement-induced thermogenesis. However, during periods of prolonged inactivity, a different model was required, which included a component of extra metabolic activity, termed supplementary thermogenesis. By fitting this model to data at 28 and 21 degrees C, it was possible to partition 24 h heat production into the three possible sources of underlying, movement-induced and supplementary thermogenesis. 4. Total 24 h heat production was approximately 25% higher for rats at 21 compared with 28 degrees C (P less than 0.01) and underlying thermogenesis was approximately 20% higher for those in the mild cold (P less than 0.01). Measured movement was significantly reduced in the mild cold (P less than 0.05) although it was energetically less efficient since there was no difference in movement-induced thermogenesis, which accounted for 18 and 15% of total heat production at 28 and 21 degrees C respectively. Supplementary thermogenesis was observed only in the mild cold and it accounted for approximately 6% of 24 h heat production, while the peak value accounted for 20% of total heat production. Circadian variations in thermogenesis were also different at 28 compared with 21 degrees C. Possible mechanisms accounting for the components of underlying thermogenesis and supplementary thermogenesis are discussed.

Animals↗
PubMed1991

Calculating the energy values of foods: towards new empirical formulae based on diets with varied intakes of unavailable complex carbohydrates.

A statistical analysis has been made by generalised linear regression of the relationship between the availability of digestible energy (DE) and the intakes of dietary gross energy (E) and of dietary 'fibre' or unavailable complex carbohydrate (U), for published observations on 43 human diets with varied intakes and sources of U (2-93 g daily) and varied intakes of E (7598-15104 kJ or 1816-3610 kcal daily). Simple formulae were devised also for the availability of metabolizable energy (ME) assuming urinary energy losses of 30 kJ or 7 kcal/g nitrogen (N) intake. For the calculation of DE and ME in mixed human diets with accuracy greater than obtained with previously published methods, the following linear formulae are proposed and their limitations discussed: DE (kJ) = 0.96E(kJ)-9U(g) ME (kJ) = 0.96E(kJ)-9U(g)-30N(g) DE (kcal) = 0.96E(kcal)-2U(g) ME (kcal) = 0.96E(kcal)-2U(g)-7N(g) The equations devised are used to identify atypical observations on faecal energy excretion, and their possible causes are considered. In particular diets high in whole-grain cereal cause faecal energy losses greater than predicted by these equations which is possibly explained by more carbohydrate reaching the colon than expected from current compositional analytical methods.

Dietary Carbohydrates↗
PubMed1990

The biological effects and digestible energy value of a sugar-beet fibre preparation in the rat.

A sugar-beet fibre preparation (SBF) was incorporated into a semi-synthetic rat diet at a level of 100 g/kg. The material caused no feed aversion, and gain of live weight was unimpaired. SBF appeared to be slightly more fermentable than wheat bran and only marginally less effective as a faecal bulking agent when compared with equalized intakes of non-starch polysaccharide. SBF did not stimulate mucosal cell turnover in the small intestine. Some enlargement of the caecum was observed in animals given SBF, but it was no greater than that of animals given wheat bran. Animals given SBF had a lower serum cholesterol concentration than both the fibre-free controls and those given wheat bran. This hypocholesterolaemic effect was less than that of guar gum however. The partial digestibility of energy for SBF was 0.64, and its partial digestible energy value was 11.3 kJ (2.7 kcal)/g. The partial digestibility of energy for non-starch polysaccharide in SBF was estimated to be 0.53 and its partial digestible energy value was 9.1 kJ (2.2 kcal)/g. This value was not significantly different from that expected for unavailable carbohydrate in mixed human diets.

Animals↗
PubMed1990

Energy balance and energy values of alpha-amylase (EC 3.2.1.1)-resistant maize and pea (Pisum sativum) starches in the rat.

Apparent and partial digestible energy values for alpha-amylase (EC 3.2.1.1)-resistant, retrograde starches, isolated from cooked maize and pea starches (RMS and RPS respectively), were determined in male Wistar rats (about 180 g) during a 28-29 d balance period with ten animals per treatment. The starches were provided as supplements (100 g/kg diet) to a semi-synthetic basal diet (B), and their effects on the apparent digestibilities of nitrogen and fat, and on gains of live weight, fat and lean tissue were examined. Diet B alone was the control; sucrose (Su) and Solka-floc cellulose (SFC) were also examined for reference. Apparent digestibilities for Su, SFC, RMS and RPS were 1.0, 0.16, 0.98 and 0.89 respectively. Whereas the apparent digestibilities of gross energy, N and fat in the diet were unaffected by supplementation with Su, each was decreased by supplementation with SFC, RMS and RPS. Partial digestible energy values calculated from the intakes and faecal losses of energy in the basal and supplemented diets were 15, 12.4 and 0.8 kJ/g for RMS, RPS and SFC respectively. These values were smaller than corresponding apparent digestible energy values calculated from the apparent digestibility of the supplement and its gross energy value. Only the Su and starch supplements increased the intake of apparent digestible energy and the gain of live weight. Both starches and Su increased total energy (and fat) deposition to almost similar extents. It is concluded that the resistant starches contribute significant dietary energy, enhance growth and elevate fat deposition to extents almost similar to Su.

Animal Feed↗
PubMed1990

Energy values of unavailable carbohydrate and diets: an inquiry and analysis.

To determine digestible-energy values (DEVs) for unavailable carbohydrate (UC), an analysis was made of published data on 29 human diets with UC from several sources and intakes ranging from 4 to 93 g/d. A distinction was made between apparent DEVs, derived from UC intake and fecal loss, and partial DEVs, derived from energy intake and fecal loss. By use of a proposed calculation, partial DEVs ranged from -20 to +10 kJ/g (-4.8 to +2.4 kcal/g) in different diets; all values were below the corresponding apparent DEVs. Factors explaining this range, including analytical problems, are considered. Rather than finding discrepancies, both the partial DEVs and the energy available from the whole diet were found to be related to the apparent digestibility of UC (r = 0.88), the proportion of the diet estimated as UC (r = 0.73), and both combined (r = 0.98). Several food-energy evaluation systems are also assessed for accuracy and the implications of these observations for food-energy evaluation are discussed.

Dietary Carbohydrates↗
PubMed1989

Utilization of alpha-amylase (EC 3.2.1.1) resistant maize and pea (Pisum sativum) starch in the rat.

1. The extent of utilization of alpha-amylase (EC 3.2.1.1)-resistant retrograded starches in vivo was assessed in male Wistar rats (about 100 g body-weight). All animals were given a fibre-free semi-synthetic basal diet (SS) containing sucrose as the only carbohydrate source, ad lib., for 13 d. On day 14, after an overnight fast, rats were allocated to one of five dietary treatments (n 30):1, fibre-free basal SS diet; 2-5, basal SS diet supplemented with 100 g sucrose, Solka floc (cellulose), resistant maize starch (RCS) or resistant pea (Pisum sativum) starch (RPS)/kg diet. Animals allocated to each dietary treatment were divided into three groups of ten rats which were given the appropriate diet for 8 or 9, 17 or 18 and 29 or 30 d (8/9, 17/18 or 29/30 d groups respectively). Rats were fed on 12 g diet/d (treatment 1) or 13.2 g diet/d (treatments 2-5) for the first 20 d, and 14 or 15.4 g/d respectively until the end of the experiment. Rats fed on the supplemented basal diets were thus given 10% more food to allow for the addition of the test carbohydrate. Faecal carbohydrate excretion was determined at intervals in the 17/18 d groups. At the end of each experimental period animals were killed after consuming their daily food ration and small intestinal length, weight of caecal and ileal contents and tissue, and pH of caecal contents measured. The amount of carbohydrate in the caecal and ileal contents from the 8/9 and 17/18 d groups was determined. 2. Weights of ileal and caecal contents, caecal tissue and faecal output were significantly greater at all time points for rats fed on the resistant starches compared with those fed on basal and sucrose-supplemented diets. Values were higher for RPS-fed rats than for RCS-fed rats. 3. The quantity of carbohydrate recovered from ileal and caecal contents showed that both RCS and RPS were partially digested and absorbed as carbohydrate, but that RPS was digested to a lesser extent. 4. The concentration of carbohydrate decreased between the ileal and caecal sites when RPS and RCS were given but was essentially unchanged when cellulose was given. This is consistent with rapid fermentation of a fraction of these starches. 5. Faecal carbohydrate elimination in the 17/18 d groups fed on RCS and RPS declined with time, which suggested an adaptive response resulting in increased utilization of the starches. This adaptive response was slower in the RPS-fed rats than the RCS-fed rats.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗