Biomedical subjects

A Z Belko

Publications and source records attributed to A Z Belko.

13 recordsLinked to original sources

PubMed1996

Body fat percentage and gender: associations with exercise energy expenditure, substrate utilization, and mechanical work efficiency.

Energy expenditure (EE) was measured at specific steady-state work rates to determine if body fat percentage or gender was associated with exercise EE, substrate oxidation, or work efficiency. Body fat percentage (leaner vs. fatter men, 9-15% vs. 20-25% fat; leaner vs. fatter women, 16-24% vs. 32-48% fat) was not related to work efficiency or submaximal EE. Fatness affected substrate oxidation in men but not in women. Compared to fatter men, leaner men had higher fat oxidation (6.7 +/- 1.6 vs. 1.4 +/- 2.0 mg.kg fat-free mass [FFM]-1.min-1; p < .01) and lower carbohydrate oxidation (26.6 +/- 4.2 vs. 39.3 +/- 5.0 mg.kg FFM-1.min-1; p < .01) at 60% VO2max. When men and women of similar fatness and relative aerobic capacity were compared, men had higher EE measured as kilojoules per minute but similar rates of EE and substrate oxidation per kilogram of FFM at 40-60% VO2max. It was concluded that body FFM, not fatness, is a determinant of exercise EE, whereas fatness is associated with differences in exercise substrate oxidation in men. Along with aerobic fitness, gender and fatness should be considered in future studies of exercise substrate oxidation.

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↗

PubMed1990

The effect of exercise on energy intake and body composition in overweight women.

Twelve moderately overweight women with mild obesity were studied to determine the effect of exercise on nutrient intake and body composition. The women, 16 to 42 percent above desired body weight (BW) and 30 to 41 percent body fat, rotated through three 18-day treatment periods: no exercise (NO-EX), moderate duration exercise (M-EX), and long duration exercise (L-EX). Daily exercise was prescribed to increase energy expenditure by 12.5 (M-EX) or 25 percent (L-EX) of energy intake required for BW maintenance during baseline. Diets were self-selected from a variety of conventional foods, and intake was monitored. Exercise did not affect quantity of energy intake or macronutrient composition of diets during the treatment periods. Energy and carbohydrate intakes tended to be higher in response to M-EX and L-EX compared to NO-EX during the last 5-day interval of the treatment periods, but these trends were not statistically significant. Exercise did affect BW and fat-free mass (FFM); mean FFM values were 49.3, 49.7 and 50.8 kg at the end of NO-EX, M-EX and L-EX, respectively (P = 0.017). Body fat mass (FM) was not consistently affected by exercise. It appears that exercise affects FFM but has no consistent effect on nutrient intake in mildly obese women who are choosing food intake from a variety of foods.

Adipose Tissue↗

PubMed1989

Accuracy of heart-rate monitoring and activity diaries for estimating energy expenditure.

The accuracy of heart-rate monitoring and activity diaries for measuring energy expenditure in free-living individuals was studied in 12 women. Estimates of energy expenditure were calculated from heart-rate monitoring by use of four different prediction equations to describe the relationship between heart rate and energy expenditure. Estimates of energy expenditure from activity diaries were calculated using both individually measured and published values for the energy cost of activities. Energy intake adjusted for changes in body-energy stores was used as a reference. Heart-rate monitoring overestimated group energy expenditure from 2 to 9% and the errors in estimating individual energy expenditure ranged from -53 to 67%. Activity diaries underestimated group energy expenditure by 2-6% and the errors in estimating individual energy expenditure ranged from -39 to 56%. Heart-rate monitoring and activity diaries may prove useful for estimating the energy expenditure of groups but not individuals.

Activities of Daily Living↗

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↗

PubMed1987

Diet, exercise, weight loss, and energy expenditure in moderately overweight women.

The effect of a moderate energy intake plus exercise (MEEX) vs a low energy intake without exercise (LESD) on weight loss and energy expenditure was examined in two groups of moderately overweight women confined to a metabolic unit. An initial 2-week baseline period was used to determine weight maintenance energy requirement (ER). This was followed by a 6-week weight reduction period. Energy intake was decreased to 0.75 ER in MEEX and treadmill exercise was individually prescribed to increase energy expenditure to 1.25 ER. Energy intake was decreased to 0.5 ER in LESD. Thus, both energy intake and expenditure were manipulated to result in an energy deficit of 50 percent. Although total weight loss was significantly higher in LESD compared to MEEX (7.8 vs 5.7 kg), fat loss did not differ (5.1 vs 4.7 kg) hence the proportion of weight loss due to fat was greater in MEEX. Aerobic capacity, measured by maximum oxygen uptake, significantly improved in MEEX (2.44 to 2.84 l/min) but did not change in LESD (2.51 to 2.50 l/min). Basal metabolic rate, energy cost of standardized activities, and 3-hour thermic response to a test meal did not change in either group throughout the study. Thus, a 50 percent energy deficit, achieved by either diet alone or diet in combination with exercise, did not result in conservation of energy expenditure in moderately overweight women.

Adipose Tissue↗

PubMed1987

Vitamins and exercise--an update.

Although no conclusive evidence exists to suggest that vitamin supplementation improves athletic performance in nutritionally adequate individuals, exercise may increase requirements for certain vitamins in individuals with marginal vitamin stores. This review summarizes results from recent research studies of vitamins and exercise. Exercise increased the requirement for riboflavin and vitamin C; however, vitamin supplementation improved the ability to train only in vitamin C-depleted individuals. No measurable effect of supplemental thiamin, riboflavin, or vitamin B6 on performance was observed in any of the reported studies. Exercise acutely affected vitamin B6 metabolism. Confusion regarding vitamin supplementation and exercise performance may stem from a lack of adequate research data. Recommendations for future research are presented.

Female↗

PubMed1986

Effect of energy and protein intake and exercise intensity on the thermic effect of food.

The effect of energy content and protein concentration of a test meal and exercise intensity on the thermic effect of food (TEF) was examined. TEF was measured in eight men in response to meals representing 15, 30, and 45% of daily energy requirement; protein concentrations of 15, 30, and 45% of energy of the meal, and exercise intensities of 35, 50, and 65% of maximum capacity. In response to energy content of the meals, total 3-h TEF (mean +/- SEM) 4.0 +/- 0.83, 9.7 +/- 1.15, and 10.8 +/- 0.79 1 O2 for the 15, 30, and 45% meals, respectively, indicating a positive linear and a negative quadratic relationship. Although the 15% protein meal resulted in the smallest TEF, 150-270 min after the meal, total 5-h increase in oxygen consumption did not differ among the three protein meals. Exercise intensity did not alter TEF. Energy content of the test meal had the greatest effect on TEF.

Adult↗

PubMed1986

Combined effects of exercise and restriction of energy intake on moderately obese women.

The current study was designed to assess the contribution of dietary-induced weight reduction on improvements in functional capacity in moderate obesity. Twelve females (means age = 29 yr, means fat percentage = 37%) served as subjects for the study. Subjects trained on a cycle ergometer 30 min.day-1, six day.wk-1 for three or six weeks at 75 to 85 per cent of maximum heart rate (HR max). Improvements in maximal oxygen uptake (delta VO2 max I.min-1) and functional capacity (delta VO2 max ml.kg-1 min-1) were compared in an attempt to separate out training and dietary effects respectively. Measurements were also taken on both the cycle ergometer and treadmill to test for any specificity of training effects. Changes in body composition were assessed by densitometry. Following three weeks of training, there was an average increase in VO2 max ml.kg-1 min-1 on the cycle ergometer and the treadmill of 14 and 19 per cent respectively. By six weeks, this had increased to 18 and 26 per cent respectively. The contribution of weight reduction to the improvements in functional capacity was calculated to range from 20 to 33 per cent. Thus, both energy restriction and exercise training appear to be effective means of improving functional capacity in moderately obese women.

Adult↗

PubMed1985

Effects of exercise on riboflavin requirements: biological validation in weight reducing women.

The present study was designed to evaluate our previous estimates for riboflavin requirement, 0.96 mg/1000 kcal during nonexercise and 1.16 mg/1000 kcal during exercise in overweight women. Two groups of 6 weight reducing women consumed either 1.16 mg riboflavin/1000 kcal (HR) or 0.96 mg/1000 kcal (MR). The study was two, 3 period by 2 treatment (exercise or nonexercise) crossover designs, one design at each level of riboflavin. Erythrocyte glutathione reductase activity coefficients (AC) significantly increased in both groups from 1.16 +/- .02 to 1.20 +/- .03 in group HR and from 1.31 +/- .04 to 1.36 +/- .02 in the MR group during nonexercise and exercise, respectively. ACs increased in the HR group due to an increase in total enzyme activity while ACs increased in the MR group due to a decrease in basal enzyme activity reflecting decreased flavin availability. There were no differences in aerobic capacity, weight loss, nor change in lean body mass between the two groups. Thus, 0.96 mg/1000 kcal was not adequate during either nonexercise or exercise periods while the 1.16 mg/1000 kcal was adequate.

Adult↗

PubMed1984

Effects of aerobic exercise and weight loss on riboflavin requirements of moderately obese, marginally deficient young women.

In a previous study, exercise was shown to increase riboflavin requirements of active, normal weight young women. The present study examined the effect of exercise and weight loss on riboflavin status of moderately overweight women. The experiment was designed as a two-period cross-over with an initial base-line period and two 5-wk metabolic periods. The basic diet contained 1200 kcal with a riboflavin concentration of 0.8 mg/1000 kcal. Exercise consisted of a program of dance exercise. Riboflavin depletion, as measured by increased erythrocyte glutathione reductase activity coefficients and decreased urinary excretion of riboflavin, occurred during both nonexercise and exercise periods. Erythrocyte glutathione reductase activity coefficients increased from a base-line mean of 1.28 +/- 0.11 to 1.40 +/- 0.12 during nonexercise and to 1.49 +/- 0.16 during exercise. Urinary excretion of riboflavin fell from 48 +/- 12% of intake during base-line to 30 +/- 13% during nonexercise and to 19 +/- 6% during exercise. Riboflavin depletion was not related to the rate or composition of weight loss or to change in aerobic capacity.

Adult↗

PubMed1983

Effects of exercise on riboflavin requirements of young women.

The riboflavin requirement of young women during periods of sedentary living and exercise was determined during a 12-wk metabolic study. The study was divided into a 6-wk no exercise period followed by a 6-wk exercise period in which subjects jogged around a track for 20 to 50 min/day. Twelve subjects, aged 19 to 27 yr, were fed a basic diet containing 0.6 mg riboflavin/1000 kcal of intake. Riboflavin intake was increased by 0.2 mg/1000 kcal increments by provision of riboflavin in a glucose polymer mixture. Linear regression analysis was used to estimate the riboflavin intake required for an erythrocyte glutathione reductase activity coefficient of 1.25 during both the no exercise and exercise periods. Individual riboflavin requirements ranged from 0.62 to 1.21 mg/1000 kcal before exercise and 0.63 to 1.4 mg/1000 kcal during the exercise periods. Riboflavin requirement could not be related to the kilocalorie intake or lean body mass of the subjects. It is concluded that healthy young women require more riboflavin to achieve biochemical normality than the 1980 Recommended Dietary Allowances and that exercise increases riboflavin requirements.

Adult↗

PubMed1982

An in vitro system for measuring intrinsic dietary mineral exchangeability: alternative to intrinsic isotopic labeling.

The primary purpose for the in vitro system described here was to provide an alternative method to intrinsic isotopic labeling for determining exchangeability of intrinsic food mineral with extrinsic inorganic mineral or one of its isotopes. In this system, foods or food mixtures extrinsically tagged with an isotope of the mineral of interest are incubated successively in media simulating peptic or pancreatic digestion. Radioactivity and mineral measurements are made on a)the mixture before digestion and after b)peptic and c)successive peptic pancreatic (P-Pa) digestion. Exchangeability is determined by comparing the specific activity in the peptic and P-Pa digest supernatants to that in the mixture before digestion. In addition, determination of the total soluble mineral after P-Pa digestion provides a measurement of potential bioavailability. The procedure was tested for calcium (Ca) exchangeability and bioavailability from a number of foods and food combinations with 45Ca as the tracer. It could be used for any mineral, however, including non-nutrient or toxic elements. It is likely to be most useful in association with human studies carried out with extrinsic stable (non-radioactive) or short-lived radioactive isotopes that are unsuitable for intrinsic labeling.

Biological Availability↗