Mean Mass Loss Research Articles

Effects of lateral wood zone on brown rot resistance of untreated and linseed oil-impregnated Scots pine wood

Various oils can be used to lower the equilibrium moisture content and increase the service life of Scots pine wood products. The aim of this study was to investigate effects of the lateral wood zone on the brown rot resistance of untreated and linseed oil-impregnated Scots pine wood in a laboratory test (EN 113). Significant differences were found in the mean mass losses of treated and untreated specimens taken from three lateral heartwood zones, but not between specimens taken from sapwood. The treatment had no significant effect on sapwood, although it seems to have some positive effect on the durability of heartwood, apparently due to interactive effects with the high extractives contents of heartwood.

Experimental analysis of biomass pyrolysis using microwave-induced plasma

Energy-from-waste, a process that converts high calorific wastes to energy, has posed a possible renewable energy route, in addition to reducing waste volumes being sent to landfill. One technology that is effective at near complete organic–inorganic dissociation is plasma gasification. However, a precursor to generating this plasma is to create an electrical arc by a large DC current, which is highly energy intensive. This study, however, examines a novel method of producing plasma by microwaves, which is much more energy efficient. To test its suitability in waste and biomass treatment, three 10g triplicate waste wood (biomass) samples was pyrolysed using microwave-induced plasma in a lab-based reactor. The resultant gas was siphoned from the reactor exhaust pipe and characterised using a Gasmet DX400 FTIR analyser. To determine the proportion of gas flow between the siphon tube and exhaust, a mass balance model of the system was constructed. After applying the appropriate correction factor, the mean mass ratio of liquid, solid, and gas was found to be 66:20:13. The start and final masses were recorded and compared with literature values. Mean mass loss was determined to be 7.96g (79.6 wt.%), which is indicative of complete pyrolysis.

Preferences of Coptotermes formosanus Shiraki and Coptotermes gestroi (Wasmann) (Blattodea: Rhinotermitidae) among Three Commercial Wood Species.

The Formosan subterranean termite, Coptotermes formosanus Shiraki, and the Asian subterranean termite, Coptotermes gestroi (Wasmann), are both pests of wood in service in Hawaii and Florida. We conducted a laboratory study using method modified from those described in standard E1-09 of the American Wood Protection Association (AWPA 2009) to assess the termite resistance of three commercially available wood species used in regions of the USA where both termite species occur: Douglas fir, Pseudotsuga menziessii, southern yellow pine, Pinus spp. and redwood, Sequoia sempervirens. A multiple-choice (three-choice) assay was used for four weeks (28 days) in order to simulate field conditions of food choice and assess termite feeding preferences under 28 °C and 72–80% RH. 400 termites (360 workers: 40 soldiers) were released into each test jar. Five replicates and two controls of each wood species were used with each termite species. Termite mortality was recorded at the end of the test; and wood wafers were oven-dried and weighed before and after termite exposure to determine the mass loss due to termite feeding, and rated visually on a 0 (failure) to 10 (sound) scale. There were significant differences in mean mass loss values among the three wood species and between two termite species. The mean mass loss value for redwood was significantly lower than Douglas fir and southern yellow pine with both termite species. However, C. formosanus showed increased feeding on Douglas fir and southern yellow pine compared to C. gestroi.

Comparative Study of the Resistance of Six Hawaii-Grown Bamboo Species to Attack by the Subterranean Termites Coptotermes formosanus Shiraki and Coptotermes gestroi (Wasmann) (Blattodea: Rhinotermitidae).

Bamboo is widely grown and utilized as a construction material around the world, particularly in the tropics. At present, there are about 70 bamboo species and varieties recorded from Hawaii. The objective of our study was to determine the relative resistance of six Hawaii-grown bamboo species to attack by Coptotermes formosanus Shiraki and Coptotermes gestroi (Wasmann). Four-week laboratory feeding trials were performed as described in standard E1-09 of the American Wood Protection Association (AWPA 2009). Samples of each of the six bamboo species were individually exposed to 200 termites (with 10% soldiers); and termite mortality, wood mass loss, and visual appearance of the samples (on a scale of 0–10) were recorded at the conclusion of the trail. Mean mass losses of the six species as a result of termite feeding ranged from 13–29%; with the two most resistant bamboo species, Gigantocholoa pseudoarundinacea and Bambusa oldhamii, demonstrating significantly greater resistance to termite attack than the most susceptible bamboo species, Guadua anguistifolia, with both termite species. Dendrocalamus brandisii, Dendrocalamus latiflorus, and Bambusa hirose were intermediate in their termite resistance. Overall, we observed very little difference in wood preference between C. formosanus and C. gestroi. Although bamboo is a very promising construction material, and species clearly differ in their susceptibility to termite attack, all six species evaluated in the present study would require additional protection for use under conditions of high termite pressure.

Post-harvest attributes and consumer acceptability of green mealies (Zea mays) stored at ambient and refrigeration temperatures in Swaziland

Maize (Zea mays) is the staple food of the Swazi people and many traditional societies in Africa. When freshly harvested, the product is referred to as green mealies and is highly valued in Southern Africa. Green mealies are highly perishable compared to dry maize because of their high water content which affects their keeping quality. There is need therefore to find suitable post-harvest handling methods to retard deterioration processes of green mealies. Thus, the main objective of this study was to investigate the consumer acceptability of boiled green mealies which were initially stored at various temperatures ( 1.5 o C, 5°C and ambient temperature). The study also investigated the effect of storing samples under these conditions on total soluble solids (TSS) and mass loss. The study was carried out at the Food Science and Technology Laboratory of the University of Swaziland, Luyengo Campus. Two experiments were conducted where, in each experiment, there were three treatments (storage at 1.5 o C, 5 o C or ambient temperature) replicated three times. The treatments were arranged in a randomized complete block design (RCBD). Data pertaining to TSS, mass loss and sensory evaluation at 2, 4, 6, 8 and 10 days after storage were collected. Total soluble solids ranged between 2.55 and 6.3% and mean mass loss ranged from 2.68 to 11.53 % by the end of the experiment. There were significant (p<0.05) differences with respect to the acceptance of the samples from various storage temperatures by a consumer panel. Green mealie bread or bolied green mealies previously stored at 1.5 o C were most accepted by consumers followed by samples stored at 5 o C and lastly those stored at ambient temperature. All the samples of green mealies lost quality to a certain extent during storage which showed that loss of quality can not be stopped but can be minimised.

Variability in The Natural Termite Resistance of Plantation Teak Wood and its Relations With Wood Extractive Content and Color Properties

Property of natural termite resistance of teak ( T ec tona g r an d i s ) wood signifies one of its most important characteristics. With the purpose of understanding the variation in such resistance, four teak trees in the form of trunk (stem) from Randublatung , Central Java were randomly selected, and each wood portion sampled in radial and axial direction. Extractive content and color properties of the teak wood were also measured and correlated with properties of its natural termite resistance. Bioassay test was conducted by no-choice feeding method using R e t ic u l i t e r m e s spe r a tus Kolbe termites. The extractive contents were determined by successive extraction using n -hexane, ethyl acetate, and methanol, respectively. Color properties were measured with the CIELAB system. Results showed that antitermitic activity of the teak wood was affected by radial and axial position in the corresponding tree. The wood from middle part of the trees in axial direction exhibited the most resistant to termites (mean mass loss = 1- 4 mg ), while in radial direction the sapwood exhibited the least resistance ( greatest mass loss), and moving inward to the near-pith heartwood the resistance tended to decrease somewhat (slight increase of mass loss). Heartwood and sapwood part differed significantly in ethyl acetate and methanol- soluble extractive contents. Apparently, the greater the ethyl-acetate-soluble extractives (EEC) then the higher the termite resistant (lower mass loss), and conversely the greater the methanol- soluble extractive (MEC) then the lower the termite resistant ( greater mass loss). The brightness index (L*) and redness index (a*) varied significantly in radial direction, however, no significant variation was found in color properties within the heartwood. No strong degree correlation was measured between the mass loss due to termite activity and extractive content parameters. In both heartwood and sapwood, a significant negative correlation ( r = -0.50) was found between the mass loss and redness (a*), while correspondingly a significant positive correlation ( r = +0.54) occurred between brightness and mass loss. These occurring phenomena strongly suggested that the red colored teak wood was brought about by the moderately polar EEC (e.g. tannin, quinone, and other polyphenol) that inflicted teak-wood resistance against termite (lower mass loss), while the bright-colored teak wood was due to the highly polar MEC (e.g sugar and other soluble carbohydrate) which were conversely responsible for lowering termite resistance ( greater mass loss).

The effect of stake dimension on the field performance of two hardwoods with different durability classes

Timber diversity is associated with virtually all types of wood structures for various end-uses including bridges and railway-sleepers. Some timbers resist bio-degradation and are termed naturally durable. Wood durability is influenced by numerous extrinsic and intrinsic factors; however, knowledge is scant about the role stake dimension plays. Therefore, the field performance of replicates of four dimensions (500 × 50 × 25; 250 × 25 × 12.5; 125 × 12.5 × 6.25; and 62.5 × 6.25 × 3.13 mm) from two commercially important hardwoods ( Milicia excelsa and Sterculia rhinopetala) of different durabilities (i.e., high and moderate, respectively) was investigated for 5 years using the graveyard method with non-durable Ceiba pentandra as a control. Durability parameters assessed were visual durability ratings, hardness, and mass losses. C. pentandra usually performed worst in all parameters. Generally, a steady increase exists in degradation from the thickest stakes (500 × 50 × 25 mm) to the thinnest (62.5 × 6.25 × 3.13 mm). Thus, the greater the stake dimension, the smaller its visual durability rating, mass and hardness losses (i.e. more durable). However, few discrepancies occurred, as the thinnest stakes were often buried deep in the soil, decreasing their chances of getting attacked. M. excelsa remained harder and more durable for stakes of all dimensions (especially the thickest) than those of S. rhinopetala. However, the thinnest M. excelsa stakes unexpectedly recorded mean mass loss of 4.9%, compared with 2.1% for S. rhinopetala. The study shows wood dimension significantly affects its durability, which would inform timber engineers about their wood dimension choices for appropriate end-uses.

Litter quality and decomposition of Vitis vinifera L. residues under organic and conventional farming systems

In viticulture, residue decomposition may be important in terms of fertilization, due to the low grapevine nutritional demands. Grapevine residue quality, mass loss and nutrient release rates were studied in an organic (Vorg) and a conventional vineyard (Vconv) for 19-months. Leaf and cane residues of the Vorg (Lorg, Corg) and of Vconv (Lconv, Cconv) were buried in litterbags in both vineyards. Lorg contained in mg g −1 526 C, 14.7 N, 1.2 P and 5.4 K; Lconv 509 C, 17.9 N, 1 P and 7.3 K; Corg 556 C, 5.7 N, 1.4 P and 6.9 K; Cconv 554 C, 7.6 N, 0.9 P and 7.7 K. Mean mass loss and N, P and K release rates ( k′ = k × 10 5) were higher in leaf ( k′ = 543, 541, 448, 725) than in cane residues ( k′ = 146, 90, 136, 494). In Vorg, mass loss and N, P and K release rates were higher in Lconv ( k′ = 904, 748, 630, 1287) than in Lorg ( k′ = 293, 357, 336, 502). For Lorg, mass loss and N release rates and for Corg mass loss rate were lower in Vorg ( k′ = 293, 357, 102) than in Vconv ( k′ = 537, 541, 218). For Lconv, mass loss and N and K release rates were lower in Vconv ( k′ = 440, 518, 557) than in Vorg ( k′ = 904, 748, 1287). Incorporation of plant residues in Vconv allowed reductions of nutrient applications of 25, 2 and 21 kg ha −1 y −1 of N, P and K, respectively; in Vorg nutrient applications reduced by 7, 1, 5.5 kg ha −1 y −1.

Assessment of decay risk of airborne wood-decay fungi

The decay risk of airborne wood-decay fungi was investigated by using an air sampler. Japanese cedar disks 7.8 cm in diameter and about 3 mm in thickness with moisture content of about 100% were placed in a “BIOSAMP” air sampler and exposed to 1000 l air. Air sampling was carried out from June to September at the same sampling site in Tsukuba, Japan. The exposed disks were then incubated for 16 weeks in a damp container kept at 26° ± 2°C. During the incubation period, wood mass loss ranged from −15 to 807 mg with a mean mass loss of 244 mg. Factors affecting mass loss were explored. Wood moisture content and ratio of heartwood area proved to be significant factors. In addition, six weather factors were found to influence mass loss. Disks that were sampled on a cloudy day showed significantly higher mean mass loss compared to those sampled on a sunny day. Subculturing of filamentous fungi from 16-week incubated disks suggested one-third of the isolated fungi produced ligninolytic enzymes.

Treatment of timber with permethrin in supercritical carbon dioxide to control termites

The solubility of permethrin in supercritical carbon dioxide (scCO 2) was determined, with optimal solubility for the timber impregnation trial and the specific operating conditions examined occurring at 50 °C. Methanol as co-solvent improved solubility, but was not needed for timber impregnation. Eucalyptus obliqua heartwood (a refractory timber), Pinus radiata sapwood and P. radiata LVL were impregnated in a treatment cylinder, and their resistance to attack by termites was compared to that of material protected with standard permethrin treatments using light organic solvent preservative (LOSP). Termite field tests were conducted against Coptotermes acinaciformis and Mastotermes darwiniensis. The choice of solvent system did not affect permethrin efficacy in P. radiata sapwood against termites. P. radiata LVL specimens treated using scCO 2 had slightly lower mean mass losses than those impregnated with LOSP, reflecting slightly higher permethrin uptakes in the former. E. obliqua heartwood was completely destroyed by M. darwiniensis when impregnated with LOSP, but was mostly sound when scCO 2 was used. These results show that scCO 2 did not alter the effectiveness of the insecticide, while giving the added benefit of allowing the impregnation of timbers previously considered refractory to treatment.

A new glacier inventory on southern Baffin Island, Canada, from ASTER data: II. Data analysis, glacier change and applications

AbstractDespite its large area covered by glaciers and ice caps, detailed glacier inventory data are not yet available for most parts of Baffin Island, Canada. Automated classification of satellite data could help to overcome the data gaps. Along-track stereo sensors allow the derivation of a digital elevation model (DEM) and glacier outlines from the same point in time, and are particularly useful for this task. While part I of this study describes the remote-sensing methods, in part II we present an analysis of the derived glacier inventory data for 662 glaciers and an application to glacier volume and volume-change calculations. Among other things, the analysis reveals a mean glacier elevation of 990 m, with a weak dependence on aspect and a close agreement of the arithmetic mean with the statistical mean elevation as derived from the DEM. A strong scatter of mean slope is observed for glaciers &lt;1 km2, and the derived glacier thickness differs by a factor of two for glaciers of the same size. For the period from about 1920 to 2000 the relative area change is –12.5% (264 glaciers), with a strong dependence on glacier size. Mean mass loss as derived from volume changes is about –0.15 mw.e. a–1.

Physical function improvements after laparoscopic Roux-en- Y gastric bypass surgery

Background Obesity is a risk factor for impaired physical function and disability, with the degree of impairment most compromised in extreme obesity. Mild-to-moderate weight loss has been shown to improve function in older adults. The impact of laparoscopic Roux-en- Y gastric bypass surgery on weight loss and physical function in morbidly obese individuals was assessed. Methods This longitudinal, observational study followed up 28 morbidly obese men and women (body mass index ≥40.0 kg/m 2) for 12 months after laparoscopic Roux-en- Y gastric bypass. Physical function (self-report using the Fitness Arthritis and Seniors Trial disability questionnaire; performance tasks using the Short Physical Performance Battery and a lateral mobility task); strength (maximal isometric knee torque); and body composition measured using bioelectrical impedance were determined before surgery (baseline) and at 3 weeks, 3 months, 6 months, and 12 months after surgery. Results The 12-month weight loss was 34.2% (excess weight loss 59.8%), with a mean fat mass loss of 46 kg and a loss of fat free mass of 6.6 kg. The performance tasks and self-reported questionnaire scores had improved by 3 months after surgery compared with baseline, with selected measures showing less impairment and disability in as few as 3 weeks after surgery. Muscle quality, as measured using the maximal torque per kilogram body weight, was greater at 6 months than at baseline. Conclusion The results of our study have shown that in morbidly obese individuals with a high risk of mobility impairments, surgical procedures to reduce body weight increase mobility and improve performance of daily activities in as few as 3 weeks after gastric bypass surgery.

Short-Term Nitrogen Leaching Potential Of Fresh and Composted Beef Cattle Manure Applied to Disturbed Soil Cores

Although fresh beef cattle (Bos taurus) manure has traditionally been applied to cropland in southern Alberta, there has been a recent increase in application of composted manure to cropland in this region. Nitrogen leaching from fresh manure (FM) versus composted (CM) beef cattle manure application has not been investigated in this region. Our objective was to compare short-term (# 23 d) N leaching potential of NO3 -N and NH4 -N under increasing rates (0, 13, 39, 77 Mg ha−1 dry wt.) of FM and CM applied to a clay loam soil under uniform soil and simulated environmental conditions. Amendments were applied and incorporated into repacked 15-cm soil (surface Ah horizon) cores, incubated for 15 d, and then leached under constant-head and saturated conditions in the laboratory. An unamended control (CON) was also used. Leaching potential of NO3-N and NH4-N depended on how the N leaching variable was expressed: peak concentration vs flow-weighted mean concentration (FWMC) vs mass loss vs recovery in leachate. Peak concentrations of NO3-N were at least 90% greater for CM (125.8 mg L−1) than FM (66.3 mg L−1) and the CON (60.5 mg L−1) treatments. The FWMC of NO3-N was significantly (P # 0.05) greater for CM (21.0 mg L1) than FM (16.3 mg L−1). Recovery of NO3-N in leachate as a percentage of total N applied was significantly greater for CM (4.7%) than FM (0.8%). Peak concentrations of NH4-N, FWMC of NH4-N, mass loss of NO3 and NH4, and recovery of NH4, were similar between FM and CM. These results suggest that short-term N leaching potential of CM was greater than FM for peak concentration, FWMC, and recovery of NO3-N.

Variation in the natural termite resistance of teak (Tectona grandis Linn. fil.) wood as a function of tree age

• Tree age is one of the most important factors to affect the natural durability of wood. • The purpose of this study was to determine the natural termite resistance of heartwood and sapwood of teak (Tectona grandis Linn. fil.) for trees aged 8, 30 and 51 years. Reticulitermes speratus Kolbe was employed as a test termite using a no-choice feeding method. • The heartwood and sapwood of all of the trees tested exhibited antitermitic activity. Based on the mean mass loss due to termite activity, the sapwood and heartwood regions of 8-year-old trees are the most susceptible to termites while the heartwood regions of the 30-year-old trees showed termite resistance similar to the termite resistance of 51-year-old trees. • The mass loss is moderately correlated with n-hexane extractive content, total extractive content, brightness and redness of the wood.

Responses of Old-field Mice (Peromyscus Polionotus) to Consecutive Days of Live Trapping

We investigated causes of body mass loss associated with consecutive days of live trapping of old-field mice (Peromyscus polionotus) on four small mammal trapping grids in central Florida USA from Mar. 2003 to Dec. 2004. Body mass of P. polionotus declined when live trapped for two consecutive days. Mean mass losses were recorded in all seasons and were significantly different in spring and summer. Temperatures inside live traps were higher than ambient temperatures. Mean number of sunflower seeds ingested was not different between day one and day two of capture, and the total number of sunflower seeds consumed explained a small amount of the variation in body mass loss. Our results suggest that sunflower seeds are not a good source of water necessary to maintain a constant body mass in P. polionotus live trapped on consecutive days, and mass loss is influenced by a combination of seasonal temperature fluctuations and physiological condition of trapped individuals.

Biological Method to Quantify Progressive Stages of Decay in Five Commercial Woods by Coriolus versicolor

Biologic agar-block method was developed that allowed wood samples to be evaluated and monitored in terms of colonization and development of the decay by Basidiomycetes fungi (Coriolus versicolor) and to be directly classified based on mean mass loss. In this research, the in vitro decay of five commercial woods by Coriolus versicolor was studied by the agar-block method. The selected wood samples were Abies alba, Populus alba, Fagus orientalis, Platanus orientalis and Ulmus glabra. The results demonstrated the strong resistance of Ulmus glabra and the lowest resistance in Fagus orientalis. The mass losses (%) were 16.8 and 42.4%, respectively. There were also a high correlation between the mass loss and apparent damage. Therefore biological evaluation of wood regarding biodegradation and the selection of wood types for various application respects will be of high priority.

Utilization of stored energy reserves during fasting varies by age and season in Steller sea lions

Nine captive Steller sea lions ( Eumetopias jubatus (Schreber, 1776), 1.75–6 years of age) were fasted for 7–14 d to test the effect of short-term fasting on changes in body mass and body condition. Trials were repeated during both the summer breeding season and the nonbreeding season in seven animals to elucidate whether there was a seasonal component to the ability of Steller sea lions to adapt to limited food resources. Mean percent mass loss per day was higher during the breeding season in juveniles (1.8% ± 0.2%·d–1) than in subadults (1.2% ± 0.1%·d–1), but there were no significant age-related differences during the nonbreeding season (juveniles, 1.5% ± 0.3%·d–1; subadults, 1.7% ± 0.3%·d–1). A decrease in the rate of mass loss occurred after the first 3 d of fasting only in subadults during the breeding season. Percent total body lipid ranged from 11% to 28% of total body mass at the initiation of fasting trials. Animals with lower initial percent total body lipid exhibited higher subsequent rates of mass loss and a lower percentage of tissue catabolism derived from lipid reserves. There was no evidence of metabolic adaptation to fasting in juveniles, which suggests that juvenile sea lions would be more negatively impacted by food limitation during the breeding season than would subadults.

Tooth structure and fracture strength of cavities

This study evaluated, in vitro, the loss of tooth substance after cavity preparation for direct and indirect restorations and its relationship with fracture strength of the prepared teeth. Sixty sound human maxillary first premolars were assigned to 6 groups (n=10). MOD direct composite cavities (Groups I, II and III) and indirect inlay cavities (Groups IV, V and VI) were prepared maintaining standardized dimensions: 2-mm deep pulpal floors, 1.5-mm wide gingival walls and 2-mm high axial walls. Buccolingual width of the occlusal box was established at 1/4 (Groups I and IV), 1/3 (Groups II and V) or 1/2 (Groups III and VI) of the intercuspal distance. Teeth were weighed (digital balance accurate to 0.001 g) before and after preparation to record tooth substance mass lost during cavity preparation. The prepared teeth were submitted to occlusal loading to determine their fracture strength using a universal testing machine at a crosshead speed of 0.5 mm/min. Data were analyzed by two-way ANOVA and Tukey test (alpha= 0.05). 1/4-inlay cavities had higher percent mean mass loss (9.71%) than composite resin cavities with the same width (7.07%). 1/3-inlay preparations also produced higher percent mean mass loss (13.91%) than composite resin preparations with the same width (10.02%). 1/2-inlay cavities had 21.34% of mass loss versus 16.19% for the 1/2-composite resin cavities. Fracture strength means (in kgf) were: GI = 187.65; GII = 143.62; GIII = 74.10; GIV = 164.22; GV = 101.92; GVI = 50.35. Statistically significant difference (p<0.05) were observed between Groups I and IV, II and V, III and VI. Higher tooth structure loss and lower fracture strength were recorded after preparation of inlay cavities, regardless of the width of the occlusal box, compared to the direct composite resin cavities.

Amount, position, and age of coarse wood influence litter decomposition in postfirePinus contortastands

Spatial variation in vegetation and coarse wood is a major source of forest heterogeneity, yet little is known about how this affects ecosystem processes. In 15-year-old postfire lodgepole pine (Pinus contorta var. latifolia Englem.) stands in Yellowstone National Park, Wyoming, we investigated how the decomposition rate varies with the position of coarse wood and other dominant structures within and among stands. Tongue depressors (TD) (made of birch (Betula sp.)) and litterbags containing herbaceous litter (HL) and needle litter (NL) were deployed for 2 years within 3 burned stands and among 17 burned stands (each 0.25 ha). Within stands, the decomposition rate varied among six microsite treatments (above and below legacy wood, below logs on the ground and elevated logs, below saplings, and on open soil). Two-year mean mass loss from all litter types was least under elevated logs (HL 34.0%, NL 8.6%, TD 3.5%) and greatest under legacy wood (HL 55%, NL 33%, TD 12%). The moisture level was consistently lowest under elevated logs and highest beneath logs on the ground. Among forest stands, 2-year mass losses from HL and TD were negatively related to the amount of elevated wood. The influence of coarse wood on litter decomposition at two spatial scales suggests that coarse-wood accumulation creates long-term spatial heterogeneity in carbon and nutrient cycles.

Resting energy expenditure and fuel metabolism following laparoscopic adjustable gastric banding in severely obese women: relationships with excess weight lost

Although adjustable gastric banding is increasingly proposed for massively obese patients, little is known about the modifications of resting metabolic rate and substrate oxidation or about metabolic determinants of weight loss following this type of bariatric surgery. To evaluate the relationships between excess weight loss, resting metabolic rate (RMR) and substrate oxidation, and to identify metabolic predictive factors of weight loss after adjustable gastric banding. Seventy-three obese nondiabetic women aged 39.1+/-10.4 years (18.4-64.8). Resting metabolic rate and substrate oxidation (indirect calorimetry), body composition (bio-impedance), lipid profile and insulin sensitivity indexes were assessed before and after (13.3+/-6.0 months, range 6.0-31.1) adjustable gastric banding. Patients were classified according to postsurgery time: group A (6-12 months, n=39); group B (12-18 months, n=21); group C (>18 months, n=13). Metabolic parameters associated with the percentage of excess weight lost (EWL) 1 year after surgery were analyzed in univariate and multivariate regressions. Mean weight loss was 26.2+/-11.4 kg. Mean fat mass loss was 17.3+/-8.1 kg. All biological parameters associated with excess weight improved after surgery. Excess weight lost at 1 year was 45.9+/-17.1% in group A, 47.4+/-17.1% in group B and 51.4+/-18.5% in group C (P=NS). Resting metabolic rate/fat-free mass (FFM) slightly decreased (28.9+/-3.26 vs 30.3+/-2.8, P<0.00001) and RMR/body weight slightly increased (18.5+/-2.8 vs 17.3+/-1.9, P<0.00001) after surgery. Respiratory quotient (0.81+/-0.06 vs 0.82+/-0.05) and FFM-adjusted lipid oxidation (1.10+/-0.41 vs 1.05+/-0.33 mg/min/kg FFM) were not significantly modified after surgery. In multiple linear regression analysis, difference in RMR/body weight, difference in energy sparing, baseline BMI and postsurgery time, were significantly and independently correlated with EWL (total R2=72.5%). Adjustable gastric banding promotes gradual but sustained weight loss and is associated with long-term conservation of lipid oxidation and energy expenditure. The individual variability in energy sparing mechanisms predicts weight loss during the first year after surgery.