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P L Mayclin

Publications and source records attributed to P L Mayclin.

10 recordsLinked to original sources
PubMed1997

Weight loss is greater with consumption of large morning meals and fat-free mass is preserved with large evening meals in women on a controlled weight reduction regimen.

The purpose of this study was to determine whether meal ingestion pattern [large morning meals (AM) vs. large evening meals (PM)] affects changes in body weight, body composition or energy utilization during weight loss. Ten women completed a metabolic ward study of 3-wk weight stabilization followed by 12 wk of weight loss with a moderately energy restricted diet [mean energy intake +/- SD = 107 +/- 6 kJ/(kg.d)] and regular exercise. The weight loss phase was divided into two 6-wk periods. During period 1, 70% of daily energy intake was taken as two meals in the AM (n = 4) or in the PM (n = 6). Subjects crossed over to the alternate meal time in period 2. Both weight loss and fat-free mass loss were greater with the AM than the PM meal pattern: 3.90 +/- 0.19 vs. 3.27 +/- 0.26 kg/6 wk, P < 0.05, and 1.28 +/- 0.14 vs. 0.25 +/- 0.16 kg/6 wk, P < 0.001, respectively. Change in fat mass and loss of body energy were affected by order of meal pattern ingestion. The PM pattern resulted in greater loss of fat mass in period 1 (P < 0.01) but not in period 2. Likewise, resting mid-afternoon fat oxidation rate was higher with the PM pattern in period 1 (P < 0.05) but not in period 2, corresponding with the fat mass changes. To conclude, ingestion of larger AM meals resulted in slightly greater weight loss, but ingestion of larger PM meals resulted in better maintenance of fat-free mass. Thus, incorporation of larger PM meals in a weight loss regimen may be important in minimizing the loss of fat-free mass.

Adipose Tissue↗
PubMed1995

Fluid changes during pregnancy: use of bioimpedance spectroscopy.

The increase in body water during pregnancy is responsible for the largest portion of weight gain and is of interest of clinical practitioners. However, assessing changes in body fluids is not easily accomplished during pregnancy. The purpose of this study was to examine the accuracy of bioelectrical impedance spectroscopy for estimating fluid volumes before, during, and after pregnancy. Ten healthy adult women were recruited for the study. Total body water (TBW) and extracellular fluid (ECF) volume were measured at baseline (preconception); 8-10, 24-26, and 34-36 wk of gestation; and 4-6 wk postpartum by deuterium oxide and NaBr dilution, respectively. Estimates of TBW and ECF were also obtained by bioimpedance spectroscopy (BIS). At baseline, mean values for dilution and BIS estimates of TBW and ECF were 33.2 +/- 4.6 (SD) vs. 31.6 +/- 6.2 liters and 15.2 +/- 1.3 vs. 16.9 +/- 2.3 liters, respectively. TBW and ECF estimated by BIS were not significantly different from the dilution values at any time point. These results suggest that BIS may be useful in estimating volumes of ECF and TBW during pregnancy.

Adult↗
PubMed1995

Evaluation of body composition by dual energy x-ray absorptiometry and two different software packages.

Dual energy x-ray absorptiometry (DXA) measures body composition, tissue distribution, bone mineral content (BMC), and bone mineral density (BMD). Differences are possible due to software versions. This investigation examined body composition, tissue distribution, BMC, and BMD measurements using a DXA (Lunar Corp., Madison, WI) with different software packages (versions 3.4 and 3.6R). Fifteen women, ages 20-40 yr, enrolled in a weight-loss study (body mass index = 28) and volunteered for body composition assessment by densitometry. BMC, BMD, and tissue distribution measurements were made using DXA. Results were analyzed once each with software versions 3.4 and 3.6R. BMC + total soft tissue, measured using DXA, was comparable to measured body weight (3.4 = 76.3 kg; 3.6R = 76.5 kg; weight = 76.5 kg). Lower BMC and BMD (5.5% and 1.8%, P < 0.01) were observed with 3.6R. Arm tissue mass was lower (1,530 g; P < 0.01) and fat declined (1,069 g; P < 0.01) with 3.6R. Leg tissue mass decreased 487 g (P < 0.01), but fat tissue increased (526 g, P < 0.01) with 3.6R. A larger fat mass (1,492 g) and lower lean mass (1,115 g) were observed with 3.6R compared with 3.4. Percent fat values by densitometry using DXA 3.4 and 3.6R were 38.1%, 39.9, and 41.9%, respectively. These results demonstrated differences in total body composition, lean and fat tissue distribution, and bone measurements from DXA software versions.

Absorptiometry, Photon↗
PubMed1994

The effects of endurance exercise with and without a reduction of energy intake on fat-free mass and the composition of fat-free mass in obese women.

OBJECTIVE: The objective of this study was to evaluate the effects of endurance exercise on fat-free mass and nitrogen balance, with energy restriction or with energy intake to meet non-exercise needs in obese women. DESIGN: The study was a 14-week metabolic control study with a 2-week baseline period for dietary stabilization followed by a 12-week period of exercise (E) with or without energy restriction (D), E or D+E. SETTING: Metabolic research unit of the Western Human Nutrition Research Center. SUBJECTS: Ten obese women between the ages of 19 and 37 years volunteered as subjects. Body weight ranged from 19% to 41% IBW and body fat was 31-40% of body weight. INTERVENTION: Women were assigned to either an energy-restricted or energy-'adequate' group so that group means for weight, body fat, FFM, predicted VO2max and RMR were similar. Data were polled for the 2-week baseline period and in 3-week intervals during the intervention period. RESULTS: The data indicated that E had a slower rate of weight loss and a lower loss of FFM than D+E. Nitrogen balance was more positive in E than D+E. Negative N balance occurred in the D+E group when blood was drawn. There was no decrease in N excretion to compensate for blood losses. N balance for E was positive throughout the study. CONCLUSION: Changes in FFM, assessed by total body electrical conductivity, were different from the results obtained by classic nitrogen balance. This suggests that losses were due to fluid losses, which were confirmed by deuterium dilution procedures. This study demonstrated that body protein stores remained intact during periods of increased energy expenditure and dietary restriction in obese women.

Adipose Tissue↗
PubMed1992

Brief communication: changes in thermogenesis and caloric efficiency with high and normal protein-reducing diets in women.

A pilot study with four women (40-60% above ideal weight, 32-42 years old) was conducted for 6 weeks of weight maintenance, 12 weeks at 50% calories (1000 and 1200 kcal/day) and 6 weeks of weight maintenance after weight loss. Two women consumed 17% and two 32% of their calories from protein during restriction; their energy metabolism and body composition changes were examined. The use of doubly labeled water for measuring energy expenditure during weight loss was evaluated. Although the 32% protein diet did not reduce lean body tissue loss, the apparent increased efficiency of calorie utilization compared to the 17% protein diet is worthy of further investigation. Thermic effect of a meal was greatly reduced in these women compared to previously reported responses. Further refinements of the doubly labeled water method are needed prior to application in weight loss studies.

Adult↗
PubMed1992

Use of multi-frequency bioelectrical impedance analysis for the estimation of extracellular fluid.

Thomasset (Lyon Medicine (1962): 207, 107-118; (1963): 209, 1325-1350; (1965): 214, 131-143) and others suggested that low-frequency impedance measurements could be used to estimate extracellular fluid and that high-frequency measurements could be used for the assessment of total body water. It was the purpose of this study to examine the relationship between body fluid compartments and multi-frequency bioelectrical impedance analysis (MF-BIA). Total body water (TBW) and extracellular fluid (ECF) were measured using deuterium and sodium bromide dilution procedures. Intracellular fluid volume (ICF) was calculated as the difference between TBW and ECF. A tetrapolar arrangement of surface electrodes was used to measure whole-body resistance (R), reactance (Xc), impedance (Z), and phase angle (P) at 25 frequencies ranging from 1 kHz to 1.35 MHz. Subjects (n = 60; 40 male and 20 female) were between the ages of 19 and 65 years. Mean ratios (+/- SEM) of ECF/ICF and ECF/TBW were 0.83 +/- 0.021 and 0.45 +/- 0.011, respectively. Individuals with the largest fat-free mass (FFM) had the highest ECF value. Whole-body resistive index values most correlated to ECF were at 224, 300, 400, 548 and 1 kHz with correlations ranging from 0.93 to 0.84. All possible subset regression analysis was used to develop a prediction equation for ECF: R2 = 0.924 and SEE = 1.061: ECF = 5.17753 + (0.09989*RI224) + (0.09322*WT) - (1.3962*SEX), where RI = resistive index (HT2/R) at the specific frequency of 224kHz; WT = weight in kilograms; sex was dummy-coded, males = 0, females = 1.

Adult↗
PubMed1992

Body composition assessment: dual-energy X-ray absorptiometry (DEXA) compared to reference methods.

The use of dual energy X-ray absorptiometry (DEXA) for the assessment of body composition was examined in 55 adults (26 male & 29 female) ranging in age from 19 to 65 years. DEXA measures of bone mineral content (BMC, g), bone mineral density (BMD, g/cm2) and soft tissue (ST) were based on differential energy attenuation at dual energy levels of 40 and 70 keV. The ratio of the low- to high-energy attenuation in ST was used to quantify fat (%FatDEXA) and fat-free mass minus the bone component (FFMDEXA). BMC and BMD were significantly correlated (r = 0.82 and 0.60) with densitometric fat-free mass (FFMD). No significant differences were observed between the sum of FFMDEXA + BMC versus FFMD for either the males or females (males: FFMDEXA + BMC = 61.7 kg; FFMD = 59.1 kg; females: FFMDEXA + BMC = 43.8 kg; FFMD = 42.8 kg). Percentage body fat from DEXA for the women was equivalent to percentage fat from density (%FatDEXA = 30.8 versus %FatD = 32.2); however, significant differences were observed for the men (%FatDEXA = 19.4 versus %FatD = 23.5). Percentage fat differences for the men may be due to classification of individual soft tissue pixels. DEXA is reliable, easy to use, and appears to give accurate values for the estimation of FFM for both men and women. Additional research is needed to ascertain the cause of the differences in the estimation of percent body fat for men.

Absorptiometry, Photon↗
PubMed1988

Total-body electrical conductivity method for estimating body composition: validation by direct carcass analysis of pigs.

Determination of body composition by measuring total-body electrical conductivity (TOBEC) is based on the principle that body fat and fat-free mass (FFM) differ in electrical properties. In humans, we are able to estimate body composition only by indirect methods, which have been used to validate the TOBEC instrument. Relationships between TOBEC and body composition were examined using direct carcass analysis of 24 pigs differing widely in body weight and composition (48-137 kg and 14-45% fat, respectively). Highly significant correlations (p less than 0.0001) were found between body conductivity and empty-body water (H2O) (r = 0.979), empty-body FFM (r = 0.980), empty-body crude protein (r = 0.962), and empty-body potassium (r = 0.949). Prediction of empty-body H2O or FFM from TOBEC had a SEE of 2.1 or 2.8 kg, respectively. Thus, the TOBEC method can predict body H2O and FFM over a wide range of body weight and fatness.

Adipose Tissue↗
PubMed1987

Use of total-body electrical conductivity for monitoring body composition changes during weight reduction.

The ability of a new total-body electrical conductivity instrument (TOBEC) to monitor changes in body composition during weight reduction was examined. Twelve moderately overweight women were confined to a metabolic unit for a period of 8 wk, 2-wk baseline and 6-wk reduction periods, during which changes in body composition were assessed by densitometry and hydrometry. Additionally, TOBEC measures were taken to predict lean body mass (LBM) changes. A total of 6.6 kg body weight was lost during the 6-wk reduction period. A decline in LBM was observed during the first 3 wk of reduction, from 47.4 to 45.7 kg, with no further LBM decline observed. Changes observed in the TOBEC phase value corresponded to the observed changes in LBM and total body water (TBW) during baseline and reduction periods. TOBEC was sensitive to small changes in LBM and TBW and may be useful for monitoring composition changes during nutritional intervention programs.

Adult↗