Fructose, weight gain, and the insulin resistance syndrome

This review explores whether fructose consumption might be a contributing factor to the development of obesity and the accompanying metabolic abnormalities observed in the insulin resistance syndrome. The per capita disappearance data for fructose from the combined consumption of sucrose and high-fructose corn syrup have increased by 26%, from 64 g/d in 1970 to 81 g/d in 1997. Both plasma insulin and leptin act in the central nervous system in the long-term regulation of energy homeostasis. Because fructose does not stimulate insulin secretion from pancreatic beta cells, the consumption of foods and beverages containing fructose produces smaller postprandial insulin excursions than does consumption of glucose-containing carbohydrate. Because leptin production is regulated by insulin responses to meals, fructose consumption also reduces circulating leptin concentrations. The combined effects of lowered circulating leptin and insulin in individuals who consume diets that are high in dietary fructose could therefore increase the likelihood of weight gain and its associated metabolic sequelae. In addition, fructose, compared with glucose, is preferentially metabolized to lipid in the liver. Fructose consumption induces insulin resistance, impaired glucose tolerance, hyperinsulinemia, hypertriacylglycerolemia, and hypertension in animal models. The data in humans are less clear. Although there are existing data on the metabolic and endocrine effects of dietary fructose that suggest that increased consumption of fructose may be detrimental in terms of body weight and adiposity and the metabolic indexes associated with the insulin resistance syndrome, much more research is needed to fully understand the metabolic effect of dietary fructose in humans.

Evaluating a 'non-diet' wellness intervention for improvement of metabolic fitness, psychological well-being and eating and activity behaviors

CONTEXT

Current public health policy recommends weight loss for obese individuals, and encourages energy-restricted diets. Others advocate an alternative, 'non-diet' approach which emphasizes eating in response to physiological cues (eg hunger and satiety) and enhancing body acceptance.

OBJECTIVE

To evaluate the effects of a 'health-centered' non-diet wellness program, and to compare this program to a traditional 'weight loss-centered' diet program.

DESIGN

Six-month, randomized clinical trial.

SETTING

Free-living, general community.

PARTICIPANTS

Obese, Caucasian, female, chronic dieters, ages 30-45 y (n=78).

INTERVENTIONS

Six months of weekly group intervention in a non-diet wellness program or a traditional diet program, followed by 6 months of monthly after-care group support.

OUTCOME MEASURES

Anthropometry (weight, body mass index); metabolic fitness (blood pressure, blood lipids); energy expenditure; eating behavior (restraint, eating disorder pathology); psychology (self-esteem, depression, body image); attrition and attendance; and participant evaluations of treatment helpfulness. Measures obtained at baseline, 3 months, 6 months and 1 y.

RESULTS

(1 y after program initiation): Cognitive restraint increased in the diet group and decreased in the non-diet group. Both groups demonstrated significant improvement in many metabolic fitness, psychological and eating behavior variables. There was high attrition in the diet group (41%), compared to 8% in the non-diet group. Weight significantly decreased in the diet group (5.9+/-6.3 kg) while there was no significant change in the non-diet group (-0.1+/-4.8 kg).

CONCLUSIONS

Over a 1 y period, a diet approach results in weight loss for those who complete the intervention, while a non-diet approach does not. However, a non-diet approach can produce similar improvements in metabolic fitness, psychology and eating behavior, while at the same time effectively minimizing the attrition common in diet programs.

Conjugated linoleic acid supplementation in humans: effects on fatty acid and glycerol kinetics

Recent studies with mouse adipocytes have shown that dietary conjugated linoleic acid (CLA) may reduce body fat by increasing lipolysis. The present study examined the effect of CLA supplementation on fatty acid and glycerol kinetics in six healthy, adult women who were participating in a controlled metabolic ward study. These women were fed six CLA capsules per day (3.9 g/d) for 64 d following a baseline period of 30 d. The subjects were confined to a metabolic suite for the entire 94-d study, where diet and activity were controlled and held constant. The rate of appearance (Ra) of glycerol, which indicates lipolytic rates, was similar at baseline and after 4 wk of CLA supplementation at rest (1.87 +/- 0.21 and 2.00 +/- 0.39 micromol/kg/min, respectively) and during exercise (7.12 +/- 0.74 and 6.40 +/- 0.99 micromol/kg/min, respectively). Likewise, the Ra of free fatty acids (FFA) was not significantly different after 4 wk of dietary CLA at rest (2.72 +/- 0.06 and 2.74 +/- 0.12 micromol/kg/min, respectively) or during exercise (6.99 +/- 0.40 and 5.88 +/- 0.29 micromol/kg/min, respectively). CLA supplementation also had no effect on the percentage of FFA released from lipolysis that were re-esterified. The apparent rate of FFA re-esterification was 65.2 +/- 4.2% at rest and 32.1 +/- 3.44% during exercise. Four weeks of CLA supplementation had no significant effect on fatty acid or glycerol metabolism in healthy, weight-stable, adult women.

Influence of cognitive eating restraint on total-body measurements of bone mineral density and bone mineral content in premenopausal women aged 18-45 y: a cross-sectional study

BACKGROUND

We examined the relation between cognitive eating restraint (CER) and total-body measurements of bone mineral density (BMD) and bone mineral content (BMC).

OBJECTIVE

Our objective was to determine whether women with CER had lower total-body BMD and BMC than did other women.

DESIGN

Premenopausal women, 90-150% of ideal weight, had measurements of their BMD and BMC made and completed questionnaires on physical activity, weight history, body size satisfaction, dieting history, eating behavior, and childbearing history. Bone measurements were examined for differences between groups with low and high CER scores by using analysis of covariance and quartiles of body weight to adjust for body size differences. CER was assessed by using the Three-Factor Eating Inventory and was defined as a score > or =9; normal eating restraint (NER) was defined by a score <9. Total-body BMC, BMD, and fat and lean masses were measured by dual-energy X-ray absorptiometry.

RESULTS

Fifty-two percent of the women were classified as having CER. Women with CER were significantly more dissatisfied with their bodies. Analysis of covariance, with weight as the covariate, indicated a significant difference in BMC between women in preplanned pairs from the 5 lowest and 5 highest CER levels. No significant differences in BMD were observed between groups. Significantly lower BMC was found in women with high CER scores and body weights <71 kg than in those with high CER scores and weights > or =71 kg.

CONCLUSIONS

BMC was significantly differently between women with low and high CER scores. BMC was significantly lower in women with body weights <71 kg and classified with CER. Lower BMC in women with high CER scores may indicate an increased risk of osteoporosis.

Conjugated linoleic acid supplementation in humans: effects on body composition and energy expenditure

Recent animal studies have demonstrated that dietary conjugated linoleic acid (CLA) reduces body fat and that this decrease may be due to a change in energy expenditure. The present study examined the effect of CLA supplementation on body composition and energy expenditure in healthy, adult women. Seventeen women were fed either a CLA capsule (3 g/d) or a sunflower oil placebo for 64 d following a baseline period of 30 d. The subjects were confined to a metabolic suite for the entire 94 d study where diet and activity were controlled and held constant. Change in fat-free mass, fat mass, and percentage body fat were unaffected by CLA supplementation (0.18+/-0.43 vs. 0.09+/-0.35 kg; 0.01+/-0.64 vs. -0.19+/-0.53 kg; 0.05+/-0.62 vs. -0.67+/-0.51%, placebo vs. CLA, respectively). Likewise, body weight was not significantly different in the placebo vs. the CLA group (0.48+/-0.55 vs. -0.24+/-0.46 kg change). Energy expenditure (kcal/min), fat oxidation, and respiratory exchange ratio were measured once during the baseline period and during weeks 4 and 8 of the intervention period. At all three times, measurements were taken while resting and walking. CLA had no significant effect on energy expenditure, fat oxidation, or respiratory exchange ratio at rest or during exercise. When dietary intake was controlled, 64 d of CLA supplementation at 3 g/d had no significant effect on body composition or energy expenditure in adult women, which contrasts with previous findings in animals.

Conjugated linoleic acid supplementation in humans: effects on circulating leptin concentrations and appetite

Conjugated linoleic acid (CLA) has been demonstrated to reduce body fat in animals. However, the mechanism by which this reduction occurs is unknown. Leptin may mediate the effect of CLA to decrease body fat. We assessed the effects of 64 d of CLA supplementation (3 g/d) on circulating leptin, insulin, glucose, and lactate concentrations in healthy women. Appetite was assessed as a physiological correlate of changes in circulating leptin levels. Analysis of plasma leptin concentrations adjusted for adiposity by using fat mass as a covariate showed that CLA supplementation significantly decreased circulating leptin concentrations in the absence of any changes of fat mass. Mean leptin levels decreased over the first 7 wk and then returned to baseline levels over the last 2 wk of the study in the CLA-treated group. Appetite parameters measured at around the time when the greatest decreases in leptin levels were observed showed no significant differences between supplementation and baseline determinations in the CLA-supplemented group or between the CLA and placebo-supplemented groups. There was a nonsignificant trend for mean insulin levels to increase toward the end of the supplementation period in CLA-treated subjects. CLA did not affect plasma glucose and lactate over the treatment period. Thus, 64 d of CLA supplementation in women produced a transient decrease in leptin levels but did not alter appetite. CLA did not affect these parameters in a manner that promoted decreases of adiposity.

Relation between circulating leptin concentrations and appetite during a prolonged, moderate energy deficit in women

BACKGROUND

On the basis of observations in rodents, leptin is thought to play a key role in the regulation of energy expenditure and food intake, but less is known of its influence on ingestive behavior and energy balance in humans.

OBJECTIVE

We examined the effect in women of a chronic energy deficit on plasma leptin concentrations and self-reported appetite and explored possible relations between leptin and appetite sensations.

DESIGN

Twelve healthy women (body mass index, in kg/m2: 23-37) participated in a metabolic ward study in which 3 wk of neutral energy balance was followed by 12 wk of energy deficit (energy intake reduced by 2 MJ/d and energy expenditure increased by 0.8 MJ/d). Body weight and composition were monitored, fasting leptin concentrations were measured 4 times, and feelings of hunger, fullness, desire to eat, and prospective consumption were monitored hourly throughout the day on 7 selected days.

RESULTS

Adiposity-adjusted leptin decreased by 54% after 1 wk of a moderate energy deficit and remained low after 6 and 12 wk. Leptin was associated with self-reported hunger, desire to eat, and prospective consumption (range of r: -0.6 to -0.7, P < 0.01). The greatest hunger increase coincided with the largest percentage drop in circulating leptin and the lowest final leptin concentration. The relation between leptin and hunger was not influenced by amount of weight or body fat loss.

CONCLUSIONS

These findings support the idea that leptin is a physiologic regulator of hunger during energy deficits in humans; the role of leptin in the long-term regulation of food intake warrants further study.

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.

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.

Effect of exercise and dietary restraint on energy intake of reduced-obese women

Self-selected food intake of 15 reduced-obese women living in a metabolic ward was studied for 14 consecutive days to determine the effect of exercise and other metabolic and behavioral variables on energy intake. A choice of prepared food items were offered at breakfast, lunch and dinner, and a variety of additional food items were available continuously 24 h/day. Subjects performed either moderate intensity aerobic exercise (A-EX) (n = 8) expending 354 +/- 76 kcal/session or low intensity resistance weight training (R-EX)(n =7) expending 96 +/- kcal/session, 5 days/week. Mean energy intakes (kcal/day, +/- SEM) of the exercise groups were similar: 1867 +/- 275 for A-EX, 1889 +/- 294 for R-EX. Mean energy intakes of individuals ranged from 49 to 157% of the predetermined level required for weight maintenance. Resting metabolic rate per kg 0.75 and the Eating Inventory hunger score contributed significantly to the between subject variance in energy intake, whereas exercise energy expenditure did not. Regardless of exercise, eight women consistently restricted their energy intake (undereaters), and seven other consumed excess energy (overeaters). Overeaters were distinguished by higher Eating Inventory disinhibition (P = 0.023) and hunger (p = 0.004) scores. The overeaters' diet had a higher fat content 34 +/- 1% (p = 0.007). Also, overeaters took a larger percentage of their daily energy, than that of undereaters, 27 +/- 1 energy intake in the evening, 13 +/- 2%, compared to undereaters, 7 +/- 1% (p = 0.005). We conclude that the Eating Inventory is useful for identifying reduced-obese women at risk of overeating, and these individuals may benefit from dietary counseling aimed at reducing fat intake and evening snacking.

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.

Effects of a carotene-deficient diet on measures of oxidative susceptibility and superoxide dismutase activity in adult women

The effect of consuming a low carotene diet (approximately 60 micrograms carotene/day) on oxidative susceptibility and superoxide dismutase (SOD) activity in women living in a metabolic research unit was evaluated. The diet had sufficient vitamins A, E, and C. The women ate the diet supplemented with 1500 micrograms/day beta-carotene for 4 days (baseline), then the unsupplemented diet for 68 days (depletion), followed by the diet supplemented with > 15,000 micrograms/day carotene for 28 days (repletion). Production of hexanal, pentanal, and pentane by copper-oxidized plasma low density lipoproteins from carotene-depleted women was greater than their production of these compounds when repleted with carotene. Erythrocyte SOD activity was depressed in carotene-depleted women; it recovered with repletion. Thiobarbituric acid reactive substances in plasma of carotene-depleted women were elevated and diminished with repletion. Dietary carotene seems to be needed, not only as a precursor of vitamin A, but also to inhibit oxidative damage and decrease oxidation susceptibility.

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.

Moderate diet restriction alters the substrate and hormone response to exercise

Substrate and hormone responses to submaximal exercise were studied in 10 overweight women (119-141% ideal body weight) to learn if a moderately restricted diet would influence the responses. Subjects consumed diets with adequate energy (ADEX), N = 5, or low energy (LDEX)--50% reduction in energy, N = 5. Three times during the 12-wk study, blood was drawn before and immediately following exercise; results were combined since there were no differences between replicates. Postexercise free fatty acids and glycerol increased to 465 +/- 27 mg.l-1 in LDEX but only to 245 +/- 19 mg.l-1 in ADEX. Postexercise insulin increased to 129 +/- 13 pmol.l-1 in LDEX, but did not increase in ADEX. Postexercise growth hormone increased to 10.5 +/- 1.0 microgram.l-1 in ADEX but only to 6.6 +/- 1.0 microgram.l-1 in LDEX. All postexercise increases within diet groups were highly significant (P < 0.0001), and the postexercise responses between diet groups were also different (P < 0.01). Respiratory gas exchange indicated that both groups increased fat utilization during exercise, but diet restriction altered postexercise hormones so that fat mobilization and utilization might be inhibited. The postexercise recovery period should be studied further to determine whether diet restriction results in a sustained altered hormone pattern that would curtail lipolysis and possibly limit body fat loss.

Physiological and biochemical variables associated with body fat loss in overweight women

During a weight loss study conducted on a metabolic unit, five women lost an average of 8.7 +/- 0.7 kg of body fat mass (FM) with a 12 week treatment of low energy diet plus exercise. Another group of five women lost 4.4 +/- 0.7 kg FM with a 12 week treatment of an adequate diet plus exercise. Within each treatment, the amount of FM lost varied by approximately 2-fold. To explain the variability in FM loss, we tested its association by multiple regression analysis with several physiological and biochemical measurements obtained during a 2 week stabilization period or early in the treatment period. The variable most closely correlated with FM loss was plasma free fatty acid levels following exercise (EX-FFA). This variable alone accounted for 79 percent of the variation in FM loss. EX-FFA was simple to measure and was repeatedly correlated with FM loss, whether FFA values of the first exercise test or EX-FFA values obtained later in the experimental period were used. Of the physiological variables tested, the rate of fat calories expended in response to a test meal was correlated with FM loss and accounted for 71 percent of the variation. Upon subsequent testing, however, this relationship was not repeatable. When a treatment group designation (dummy-coded variable) was added to the regression analysis, the rate of fat calories expended at rest (FATRMR) was related to FM loss. Together, FATRMR and the dummy-coded variable accounted for 87 percent of the variation in FM loss. In a separate multiple regression equation, the combination of EX-FFA and the dummy-coded variable also accounted for 87 percent of the variation in FM loss. Further evaluation of these relationships is required to determine if EX-FFA or FATRMR would be useful as predictors of FM loss under conditions of weight loss where individuals are living freely in the community and consuming a variety of diets.

Effect of low-calorie diets on plasma retinol-binding protein concentrations in overweight women

The concentrations of total protein, albumin and retinol-binding protein, a major transport protein for vitamin A, are significantly decreased by protein-calorie malnutrition. Weight-loss diets, sometimes involving severe energy deficits over prolonged periods of time, are common in the United States. The effect, if any, of prolonged low calorie weight-loss diets with normal intakes of protein on albumin, total protein and retinol-binding protein concentrations (and potentially on vitamin A metabolism) had not been extensively studied. We measured total protein, albumin, apo + holo retinol-binding protein and holo-free- and holo-transthyretin-bound retinol-binding protein concentrations during the course of a nutritionally adequate weight-loss diet (50% calorie restriction). We found that this type of dieting did not affect total protein, albumin or apo + holo, holo-free or holo-transthretin-bound retinol-binding protein concentrations significantly. This suggests that protein intake is more critical than caloric intake for retinol-binding protein status.

Body composition of adult cystic fibrosis patients and control subjects as determined by densitometry, bioelectrical impedance, total-body electrical conductivity, skinfold measurements, and deuterium oxide dilution

This study contrasts body compositions (by six methods) of eight cystic fibrosis (CF) subjects with those of eight control subjects matched for age, height, and sex. CF subjects weighed 84% as much as control subjects. Densitometry and two bioelectrical impedance-analysis methods suggested that reduced CF weights were due to less lean tissue (10.7, 9.5, and 10.4 kg). Total-body electrical conductivity (TOBEC) and skinfold-thickness measurements indicated that CF subjects were leaner than control subjects and had less fat (5.4 and 3.6 kg) and less lean (5.2 and 7 kg) tissue. D2O dilution showed a pattern similar to TOBEC (8.3 kg less lean, 2.7 kg less fat tissue). Densitometry estimates of fat (mass and percent) were not correlated (r less than 0.74, p greater than 0.05) with any other method for CF subjects but were correlated with all other methods for control subjects. CF subjects contained less fat and lean tissue than did control subjects. Densitometry by underwater weighing is unsuitable for assessing body composition of CF patients.

Effect of total parenteral nutrition on histamine in the rat brain and other tissues

The effects of a constant infusion of total parenteral nutrition on the histamine content of the hypothalamus was studied in adult male rats. Histamine content of the stomach, kidney, liver, and heart was also determined. The relationship between tissue histamine levels and duration of the infusion was examined. Rats receiving intravenous infusions of total parenteral nutrition had significantly higher (p less than 0.001) histamine levels in the hypothalamus than did orally-fed control rats. No difference was observed in the histamine level in the remainder of the brain. Animals receiving parenterally infused nutrient solutions had a higher histamine content in the kidneys but lower histamine levels in the stomach than did the control rats. No changes in the histamine content of liver or heart were observed. It appears that increases in histamine levels in the kidney and hypothalamus of rats given total parenteral nutrition persist up to 5 days and 9 days, respectively. The mechanisms responsible for and the consequences of the alterations of histamine content of these tissues remain to be established.

Energy expenditure and physical performance in overweight women: response to training with and without caloric restriction

The metabolic effects of exercise training and the influence of a moderate calorie restriction on the training response were examined in overweight women. Ten healthy women, 119% to 141% of desirable weight, completed the 14-week study. After a 2-week stabilization period, in which diets were designed to maintain body weight (BW), five women were assigned to a 12-week experimental program of diet and exercise (D + EX) that included a 50% reduction in energy intake and a program of moderate intensity aerobic exercise 6 days per week. The other five women were assigned to the same daily exercise (EX) and continued to consume the stabilization diet. Periodic measurements of resting metabolic rate (RMR), thermic effect of food (TEF), energy cost of exercise, and predicted maximal aerobic capacity (VO2 max) were obtained, and the respiratory quotient (RQ) was determined during rest and exercise. Body composition was monitored weekly. Tests of strength and anaerobic capacity were conducted. D + EX lost an average of approximately 1.1 kg/wk, which was 67% fat, 33% lean. EX lost approximately 0.5 kg/wk, which was 86% fat, 14% lean. In both groups, the exercise program resulted in an 11% to 13% improvement in VO2 max and an 8% to 16% decrease in energy expenditure at submaximal workloads. The caloric restriction significantly increased fat utilization during exercise. The RMR declined 9% in D + EX, from 1,550 to 1,411 kcal/d, whereas it was maintained in EX, 1,608 to 1,626 kcal/d. The decrease in RMR observed in D + EX was consistent with the loss of fat-free mass (FFM).(ABSTRACT TRUNCATED AT 250 WORDS)

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.

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.

Nutritional effectors of hepatic steatosis induced by parenteral nutrition in the rat

The relative importance of three nutritional variables, nonprotein energy level, glucose-lipid calorie distribution and amino acid nitrogen level, in contributing to the steatosis that develops during a short course of parenteral nutrition was studied in intravenously fed rats. Eight infusates were tested that contained various combinations of glucose, lipid emulsion and amino acids. The infusate nonprotein energy level was the predominant effector of liver lipid content. The excessive energy level was associated with significant increments in steatosis, ranging from a 26% increase for high-fat, adequate-nitrogen infusates to a 95% increase for low-fat, adequate-nitrogen infusates. An interaction of amino nitrogen level and glucose-lipid calorie distribution also affected the severity of steatosis. The steatosis observed with inadequate-nitrogen infusates was accentuated in combination with the high-fat calorie distribution and was attenuated with the low-fat calorie distribution. The most striking effect of nitrogen inadequacy was a 3-fold increase in liver lipid content with the excessive calorie, high-fat infusates. The infusate that minimized steatosis provided energy and nitrogen at adequate levels and was low in fat content. This infusate also led to liver lipid composition and plasma lipid levels that most closely resembled those of rats fed stock diet.

Dietary evaluation of outpatients with chronic obstructive pulmonary disease

Protein-calorie malnutrition is prevalent among individuals with chronic obstructive pulmonary disease (COPD), and suboptimal body weight has been associated with increased morbidity and mortality. Pulmonary function, anthropometric measurements, and dietary intake were evaluated in 64 outpatients with stable COPD to assess interrelationships of those parameters. Those individuals with body weights less than 75% of standard for height, age, and sex had the greatest degree of airway obstruction, poorest lung diffusing capacity, and greatest loss of body fat and muscle mass. Contrary to what had been anticipated, calorie and protein intake levels were highest in the less than 75% of standard body weight group, decreased as relative body weight increased, and were lowest in the greater than 105% of standard body weight group. Those results indicate that caloric needs increase as COPD progresses. Intake levels of calcium, phosphorus, iron, vitamin A, thiamin, riboflavin, niacin, and vitamin C were adequate in terms of the RDAs and were not related to relative body weight.