Effects of binge eating behavior on fuel oxidation and body composition

OBJECTIVE: To investigate energy expenditure and glucose metabolism after a standard oral glucose load (75 g) in 8 normal weight bulimic women and 8 normal weight control women and to evaluate the relative endocrine implication. DESIGN: Serum glucose and insulin were measured both in basal conditions and after the glucose load; a basal endocrine assessment and body composition was evaluated and glucose induced thermogenesis (GIT) was calculated during 300 min following the glucose load. RESULTS: Serum glucose levels were significantly lower in bulimics both in fasting and in post-prandial state. Insulin levels were similar in bulimic and control women before and after the glucose load. FSH, leptin and free urinary cortisol (FUC) were all within the normal ranges, but significantly lower in bulimic patients compared with controls (p < 0.001). Fat mass (FM) and Fat-free mass (FFM) were reduced in bulimic patients, even if they normalized after correction per body weight. Resting energy expenditure (REE) was similar in the two groups even after FFM normalization, while GIT was lower in bulimic patients and it was strongly related to free urinary chortisol. Glucose oxidation was higher in fasting state and post glucose load, while lipid oxidation was strongly reduced. CONCLUSION: An energy preservation mechanism seems to be the key element for normal-weight bulimic patients' metabolism, consisting in leptin levels and GIT reduction, and lipid oxidation inhibition.     

Plasma Leptin Association with Body Composition and Energy Expenditure in Sickle Cell Disease

Objective: To examine the association between fasting plasma leptin concentrations and the hypercatabolic state observed in sickle cell disease (SCD).

Methods: Plasma leptin concentration and resting energy expenditure (REE) were measured in 37 SCD patients (10 men, 12 boys 14 to 18 years-old, seven women, and eight girls 14 to 18 year-old) and in 37 age, gender and fat mass (FM) matched controls. Body composition was measured hydrostatically, REE by whole room-indirect calorimeter, and plasma leptin using an RIA kit.

Results: Plasma leptin concentration and leptin normalized for body fat (ng/dL*kg FM^?1) were significantly lower in SCD patients than in non-SCD controls (4.00±3.23 vs. 9.94±14.69, p=0.021 and 0.406±0.260 vs. 0.643±0.561, p=0.024, respectively). A positive linear association between log plasma leptin and FM was observed in both males and females, adjusting for age and SCD status. The strength of this association was greater in females compared with males (slope=0.699 and 0.382 log ng/mL per 10 kg FM, respectively; p=0.013). SCD patients on average demonstrated a higher REE, adjusting for FFM (p<0.0001). Log plasma leptin and FM were not statistically significant predictors of REE after adjustment for FFM and SCD.

Conclusions: Once corrected for body composition, mean plasma leptin concentration was significantly lower among female SCD patients than among non-SCD matched controls. Although REE was higher in SCD patients, there is no simple association between leptin and REE in SCD.     

Body Composition and Energy Expenditure after Weight Loss Following Bariatric Surgery

Objectives: To assess the effectiveness of biliopancreatic diversion (BPD) in the treatment of morbid obesity and to evaluate how the procedure affects body weight.

Subjects: Fourteen morbidly obese subjects studied before and 30 months after BPD and fifteen healthy volunteers matched for age, sex and height (controls).

Methods: Comparison of the following parameters were made in the study groups before surgery and 30 months after BPD and with those of the controls group: fat mass, fat-free mass, non-protein substrate oxidation, basal metabolic rate, plasma glucose, insulin and free fatty acid concentrations.

Results: Obese subjects lost 60.38±10.71 kg of weight during 18 months following surgery and then remained stable for another 12 months, when this study was performed. Weight loss was substantially due to a loss of fat mass (FM: 60.13±13.01 kg before and 19.02±8.61 kg after BPD; p<0.001). FM were not statistically different between post-obese subjects and controls; however, post-obese patients retained significantly more fat free mass (FFM) than controls. Subsequently, basal metabolic rates of post-obese subjects were higher than those of the control group (p<0.05). Fasting non-protein respiratory quotient (npRQ) was significantly lower before BPD than 30 months after the surgery (0.798±0.04 vs. 0.90±0.048, p<0.001), suggesting that, while obese, patients oxidized more lipids than carbohydrates. Moreover, fasting and two-hour plasma glucose and insulin concentrations decreased significantly after BPD to values comparable to those of the control group.

Conclusion: Weight loss in obese patients after BPD is mainly due to lipid malabsorption, but increased energy expenditure associated with retaining a high FFM in physically active post-obese subjects may also play a role, enabling them to maintain long-term reduced body weights.     

Leptin and body weight regulation in patients with anorexia nervosa before and during weight recovery

BACKGROUND: Leptin has been considered a starvation hormone, but its role in malnourished patients is unknown. OBJECTIVE: We aimed to characterize the role of leptin in metabolic adaptation in women with anorexia nervosa (AN). DESIGN: In a cross-sectional study, 57 women with AN [mean (+/-SD) body mass index (kg/m(2)) on admission: 15.2 +/- 1.5] were compared with 49 healthy, normal-weight women (mean body mass index: 22.3 +/- 2.3). Nineteen patients were reinvestigated during weight gain 43 and 84 d after baseline. We measured serum concentrations of leptin, soluble leptin receptor, insulin, ghrelin, and thyroid hormones [thyrotropin, triiodothyronine (T(3)), and thyroxine]; fat mass (FM) and fat-free mass (FFM); resting energy expenditure (REE); energy intake; and eating behavior. RESULTS: Compared with values in the control women, leptin, T(3), REE, FM, and FFM were lower in the women with AN, but the leptin secretion rate was not significantly different. Leptin correlated with FM (r = 0.83, P < 0.001), T(3) (r = 0.68, P < 0.001), respiratory quotient (r = -0.47, P < 0.001), and REE (r = 0.58, P < 0.001). The association with REE weakened after adjustment for FFM and disappeared after further adjustment for T(3). Hunger and appetite had positive, whereas satiety and restraint had negative, associations with leptin. During weight gain (9.0 +/- 3.3 kg in 84 d), serum leptin and the leptin secretion rate increased. Changes in leptin secretion were associated with energy intake and REE. The initial changes in the leptin secretion rate (ie, the difference between baseline and 43 d) were negatively associated with changes in body weight from 43 to 84 d. CONCLUSIONS: Leptin contributes to metabolic adaptation in women with AN. The leptin response is associated with weight gain.     

Eight-Year Longitudinal Changes in Body Composition in Healthy Swiss Adults

Objective: Significant changes in body composition occur during lifetime. This longitudinal study (8.0 ± 0.8 yrs) in a cohort of healthy sedentary and physically active men (n = 78) and women (n = 53), aged 20 to 74 yr describes: 1) the longitudinal changes in weight and body composition and 2) their associations with age and physical activity.

Method: Fat-free mass (FFM) and body fat (BF) were assessed by bioelectrical impedance analysis (BIA). Subjects who regularly performed >3 hours per week of endurance type physical activity were classified as “Active”. Others were classified as “Sedentary”. Subjects were also separated by age (<45 yr vs ≥45 yr).

Results: FFM increased by 1.7 ± 2.8 kg in men <45 yr who gained 4.0 ± 5.0 kg of body weight and was maintained (0.5 ± 1.6 kg) in women <45 y who gained 1.6 ± 3.0 kg of weight. A weight gain of 1.2 ± 3.3 kg in men ≥45 yr was accompanied by stable FFM (?0.1 ± 2.3 kg), and of 1.0 ± 3.2 kg was accompanied by a loss of FFM in women ≥45 yr. In active men ≥45 yr, maintenance of FFM was associated with smaller weight gains than in sedentary; sedentary men ≥45 yr decreased FFM with larger weight gains than active subjects. Sedentary women <45 yr were able to gain FFM; the active women maintained, but did not gain FFM with smaller weight gains than in sedentary women. FFM decreased in ≥45 yr women despite of small weight gains.

Conclusion: Weight change is clearly associated with a change in FFM. Weight gain is necessary to offset age-related FFM loss between 20 and 74 yrs. In active men, a FFM increase was associated with less weight gain than sedentary men. Future studies should evaluate the threshold of weight change and the level of physical activity necessary to prevent age-related losses of FFM.     

Thermogenic response to an oral glucose load in man: comparison between young and elderly subjects

To investigate the effect of age and change in body composition on the increase in energy expenditure consecutive to the ingestion of a 75-g glucose load, respiratory exchange measurements were performed on 24 subjects, 12 elderly (mean +/- SEM, 73 +/- 1 yr) and 12 young (25 +/- 1 yr). The body weight was comparable, 62 +/- 2 kg in the elderly group vs 61 +/- 3 in the young, but the body fat content of the elderly group was significantly greater than that of the young (29 +/- 2% vs 19 +/- 2%, p less than 0.001). The elderly group presented a slight glucose intolerance according to the World Health Organization (WHO) criteria, with a 120-min plasma glucose of 149 +/- 9 mg/dl (p less than 0.005 vs young). The postabsorptive resting energy expenditure (REE) was 0.83 +/- 0.03 kcal/min in the elderly group vs 0.98 +/- 0.04 in the young (p less than 0.02); this decrease of 15% was mainly related to the decrease in fat free mass (FFM) in the elderly group, which averaged 14%. The difference was not significant when REE was expressed per kg FFM. The glucose-induced thermogenesis (GIT) expressed as percent of energy content of the load was 6.2 +/- 0.6% in the elderly group and 8.9 +/- 0.9% in the young (p less than 0.05). It is concluded that the glucose-induced thermogenesis is decreased in elderly subjects. However, when expressed per kg FFM, the increment in energy expenditure (EE), in response to the glucose load, is not different in elderly subjects, suggesting that the decrease of thermogenesis may be attributed to the age-related decrease in FFM.     

Altered postprandial glucose, insulin, leptin, and ghrelin in liver cirrhosis: correlations with energy intake and resting energy expenditure

BACKGROUND: Liver cirrhosis is associated with reduced energy intake and increased resting energy expenditure. OBJECTIVE: We aimed to investigate the possible role of glucose, insulin, leptin, and ghrelin in the pathogenesis of these alterations. DESIGN: Nutritional status, energy intake, resting energy expenditure, and fasting glucose, insulin, and leptin were assessed in 31 patients with cirrhosis. Postprandial glucose, insulin, C-peptide, leptin, and ghrelin responses were studied in a subgroup of patients after a standard meal. Ten healthy subjects served as controls. RESULTS: Patients with cirrhosis had a lower energy intake (P < 0.05), higher resting energy expenditure (P < 0.05), higher fasting leptin (P < 0.05), and higher insulin resistance (P < 0.001) than did the healthy control subjects. In the patients with cirrhosis, fasting leptin was negatively correlated with resting energy expenditure (r = -0.38, P < 0.05) but not with energy intake. In control subjects, leptin was negatively correlated with energy intake (r = -0.72, P < 0.05) but not with resting energy expenditure. The patients with cirrhosis had higher postprandial glucose (P < 0.001) and lower ghrelin (P < 0.05) concentrations at 4 h postprandially than did the control subjects. The increase in ghrelin from its minimal postmeal value to 4 h postmeal was negatively correlated (r = -0.66, P = 0.014) with weight loss in the patients with cirrhosis. Energy intake was negatively correlated (r = -0.42, P < 0.01) with the postprandial increase in glucose. CONCLUSIONS: In cirrhosis, altered postprandial glucose and ghrelin are associated with reduced energy intake and weight loss, respectively, and the effects of leptin on energy intake and expenditure seem to be altered. Insulin resistance might be involved in these altered postprandial responses.     

Changes in body composition in men and women with advanced nonsmall cell lung cancer (NSCLC) undergoing chemotherapy

Background Men with nonsmall cell lung cancer (NSCLC) are more susceptible to weight loss than women. The composition and aetiology of these gender specific weight changes are not known. Methods Measurements of body mass, body composition and energy balance (resting energy expenditure and energy intake) were made in 15 men and six women before and after chemotherapy for NSCLC. Results Over the course of chemotherapy minimal weight change was observed in both men and women. Men increased body fat from 25.0 ± 5.5 to 27.9 ± 7.9% (P < 0.05) whereas fat free mass (FFM) tended to decrease (P = 0.063). There was no change in body fat or FFM in the women. In the men resting energy expenditure decreased over the course of chemotherapy from 113.2 ± 15.9 to 105.1 ± 10.1% of the value predicted from the Harris Benedict equation (P < 0.05). In the women resting energy expenditure (REE) did not alter. Conclusion Over the course of chemotherapy for NSCLC, men and women appear to have different patterns of change in body composition and in energy expenditure.     

Long chain polyunsaturated fatty acids in neonatal nutrition.

Objective: Total body potassium (TBK) concentration is linearly correlated with the size of the body cell mass (BCM). The aim of this study was to compare BCM in normal-weight and obese individuals.

Methods: 271 individuals (207 males, 64 females), 20 to 67 years of age, participated in this study. Subjects were separated by body mass index (BMI): BMI < 25 kg/m² (BMI-L) and BMI > 25 kg/m² (BMI-H). ⁴⁰K was assessed using a whole-body counter and BCM was calculated.

Results: BCM and TBK were significantly greater in men, with a trend to be greater in women in BMI-H compared to men in BMI-L. TBK/body weight was significantly lower, while TBK/height was significantly greater for men and women in BMI-H compared to men and women in BMI-L. Fat-free mass (FFM) was significantly greater for men in BMI-H, with no significant differences in FFM between the two groups of women.

Conclusions: The healthy obese subjects in the present study had a greater BCM than the non-obese subjects. These results indicate that it is important to assess BCM in obese individuals because it could influence the type of weight loss regimen that will be used in order to preserve BCM.     

Leptin levels,leptin receptor gene polymorphisms,and energy metabolism in women

OBJECTIVE: Resting metabolic rate (RMR) is mainly determined by fat-free mass and additionally by age, sex, hormones, and possibly genetic differences. We evaluated whether leptin levels and polymorphisms in the leptin receptor (LEPR) gene were associated with energy expenditure phenotypes. METHODS: RMR, body composition, and leptin levels were measured in 125 overweight and obese women. Three LEPR polymorphisms, Lys109Arg, Gln223Arg, and Lys656Asn, were typed on genomic DNA of another group of 192 women in whom RMR was measured. Fat, protein, and carbohydrate oxidation were calculated for 103 of these subjects. In 38 subjects, glucose-induced thermogenesis was measured over 3 hours. RESULTS: In the first study group, a negative correlation between RMR and leptin levels was found after controlling for fat and fat-free mass. In multiple regression analysis, leptin contributed significantly to RMR, independent of body composition. In the second study group, RMR was not associated with LEPR polymorphisms. Differences in substrate oxidation rates were found among genotypes at the Lys656Asn site. In fasting conditions, Lys656Lys showed a trend to oxidize more carbohydrates and less fat than Asn656 carriers, a trend which became significant after the glucose load when carbohydrate oxidation rate in Lys656Lys was 15% higher than in Asn656 carriers (p = 0.04), and fat oxidation rate was 44% lower (p = 0.02). DISCUSSION: These results suggest that DNA sequence variations in the LEPR gene could affect substrate oxidation. We hypothesize that this might be caused by differences in glucose levels, leading to differences in glucose oxidation rates.     

Thermogenic response to an oral glucose load in man: comparison between young and elderly subjects.

To investigate the effect of age and change in body composition on the increase in energy expenditure consecutive to the ingestion of a 75-g glucose load, respiratory exchange measurements were performed on 24 subjects, 12 elderly (mean +/? SEM, 73 +/? 1 yr) and 12 young (25 +/? 1 yr). The body weight was comparable, 62 +/? 2 kg in the elderly group vs 61 +/? 3 in the young, but the body fat content of the elderly group was significantly greater than that of the young (29 +/? 2% vs 19 +/? 2%, p less than 0.001). The elderly group presented a slight glucose intolerance according to the World Health Organization (WHO) criteria, with a 120-min plasma glucose of 149 +/? 9 mg/dl (p less than 0.005 vs young). The postabsorptive resting energy expenditure (REE) was 0.83 +/? 0.03 kcal/min in the elderly group vs 0.98 +/? 0.04 in the young (p less than 0.02); this decrease of 15% was mainly related to the decrease in fat free mass (FFM) in the elderly group, which averaged 14%. The difference was not significant when REE was expressed per kg FFM. The glucose-induced thermogenesis (GIT) expressed as percent of energy content of the load was 6.2 +/? 0.6% in the elderly group and 8.9 +/? 0.9% in the young (p less than 0.05). It is concluded that the glucose-induced thermogenesis is decreased in elderly subjects. However, when expressed per kg FFM, the increment in energy expenditure (EE), in response to the glucose load, is not different in elderly subjects, suggesting that the decrease of thermogenesis may be attributed to the age-related decrease in FFM.     

New Reference Values for Body Composition by Bioelectrical Impedance Analysis in the General Population: Results From the UK Biobank

BackgroundLow fat-free mass (FFM) is a risk factor for morbidity and mortality in elderly and patient populations. Therefore, measurement of FFM is important in nutritional assessment. Bioelectrical impedance analysis (BIA) is a convenient method to assess FFM and FFM index (FFMI; FFM/height²). Although reference values have been established for individuals with normal body weight, no specific cutoff values are available for overweight and obese populations. Also, limited studies accounted for the age-related decline in FFM.ObjectiveTo determine BMI- and age-specific reference values for abnormal low FFM(I) in white-ethnic men and women free of self-reported disease from the general population.DesignThe UK Biobank is a prospective epidemiological study of the general population from the United Kingdom. Individuals in the age category 45 to 69 years were analyzed. In addition to body weight, FFM and FFMI were measured using a Tanita BC-418MA. Also, self-reported chronic conditions and ethnic background were registered, and lung function was assessed using spirometry.ResultsAfter exclusion of all individuals with missing data, nonwhite ethnicity, self-reported disease, body mass index (BMI) less than 14 or 36 kg/m² or higher, and/or an obstructive lung function, reference values for FFM and FFMI were derived from 186,975 individuals (45.9% men; age: 56.9 ± 6.8 years; BMI: 26.5 ± 3.6 kg/m²; FFMI 18.3 ± 2.4 kg/m²). FFM and FFMI were significantly associated with BMI and decreased with age. Percentiles 5, 10, 25, 50, 75, 90, and 95 were calculated for FFM, FFMI, and fat mass (index), after stratification for gender, age, and BMI.ConclusionsUsing the UK Biobank dataset, new reference values for body composition assessed with BIA were determined in white-ethnic men and women aged 45 to 69 years. Because these reference values are BMI specific, they are of broad interest for overweight and obese populations.     

瘦素及胰岛素拮抗与多囊卵巢综合征不孕症相关性研究

目的 分析多囊卵巢综合征(PCOS)患者血清瘦素水平及其与胰岛素抵抗的相关性,探讨二甲双胍对PCOS不孕患者的临床疗效.方法 选取86例PCOS患者和100例非PCOS健康体检者为研究对象,均分为肥胖患者和非肥胖者,调查BMI、血清瘦素、FPG、胰岛素和胰岛素抵抗指数(IR),并分析其相关性.PCOS患者随机分为A组和B组(二甲双胍治疗组),观察二甲双胍对PCOS不孕患者的临床疗效.结果 PCOS患者血清瘦素、胰岛素水平和IR均明显高于对照组,差异有统计学意义(P<0.001).PCOS患者中胰岛素抵抗者的瘦素水平显著高于非胰岛素抵抗者,差异有统计学意义(P<0.001);瘦素水平与BMI、胰岛素和IR均呈正相关(P<0.05),与FPG无明显相关性(P>0.05).B组患者排卵率(58.1%)、妊娠率(25.6%)明显高于A组(分别为27.9%、9.3%),差异均有统计学意义(P<0.05).结论 PCOS患者瘦素和胰岛素水平均明显升高,瘦素水平升高是肥胖的内在表现,胰岛素抵抗与瘦素抵抗可同时存在,血清瘦素与BMI、胰岛素和IR呈明显正相关.二甲双胍可显著提高PCOS不孕患者的排卵率和妊娠率.     

Dietary Red and Processed Meat Intake and Markers of Adiposity and Inflammation: The Multiethnic Cohort Study

Objective: The potential influence of dietary factors on inflammation is important for cancer prevention. Utilizing data from control participants (312 men, 911 women) in 2 nested case–control studies of cancer within the Multiethnic Cohort, we examined the associations of red and processed meat intake with serum levels of leptin, adiponectin, C-reactive protein (CRP), tumor necrosis factor (TNF)-α, and interleukin (IL)-6 and the mediator effect of body mass index (BMI) on the above associations (if present).

Methods: Multivariable linear models were applied to assess the association between red and processed meat intake at cohort entry and serum biomarker levels measured 9.1 years later after adjusting for covariates and to determine the mediator effect of BMI.

Results: Overall red and processed meat intake was positively associated with serum leptin levels in men (β = 0.180, p = 0.0004) and women (β = 0.167, p < 0.0001). In women, higher red and processed meat consumption was significantly associated with higher CRP (β = 0.069, p = 0.03) and lower adiponectin levels (β = ?0.082, p = 0.005). In mediation analyses with red and processed meat intake and BMI as predictors, the associations of red and processed meat with biomarkers decreased substantially (as indicated by percentage change in effect: leptin in men, 13.4%; leptin in women, 13.7%; adiponectin in women, ?4.7%; CRP in women, 7.4%) and were no longer significant (p > 0.05), whereas BMI remained significantly associated with serum leptin (men: β = 3.209, p < 0.0001; women: β = 2.891, p < 0.0001), adiponectin (women: β = ?1.085, p < 0.0001), and CRP (women: β = 1.581, p < 0.0001).

Conclusion: The current data suggest that the amount of excess body weight or the degree of adiposity may mediate the relations between dietary red and processed meat intake and serum biomarkers associated with obesity and inflammation.     

Comparison of Hormone and Glucose Responses of Overweight Women to Barley and Oats

Objective: To determine the effect of particle size (flour vs. flakes) on glycemic responses after oats and barley (Prowashonupana cultivar), which contain high amounts of soluble fiber, are consumed by overweight women.

Design: Ten women, average age 50 years and body mass index 30, consumed glucose (1 g/kg body weight) and four test meals (1 g carbohydrate/kg body weight; 2/3 of the carbohydrate from oat flour, oatmeal, barley flour, or barley flakes and 1/3 from pudding) in a Latin square design after consuming controlled diets for 2 days. Blood samples were collected at fasting and periodically after each meal.

Results: Peak glucose and insulin levels after barley were significantly lower than those after glucose or oats. Glucose areas under the curve (AUCs) after test meals compared with AUCs after glucose were reduced after both oats and barley (29–36% by oats and 59–65% by barley) (p < 0.002). Insulin AUCs after test meals compared with glucose AUCs were significantly reduced only by barley (44–56%) (p < 0.005). Indexes for insulin resistance (HOMA, MFFM, Cederholm) after the oat and barley meals were not different from indexes after the glucose meal. Glucagon and leptin responses did not significantly differ for the carbohydrates tested.

Conclusions: Particle size of the oats or barley had little effect on the glycemic responses. Both oat and barley meals reduced glycemic responses; the high soluble fiber content of this barley appeared to be a factor in the greater reduction observed.     

Basal metabolic rate in anorexia nervosa: relation to body composition and leptin concentrations

BACKGROUND: Leptin is thought to represent a peripheral signal involved in the regulation of energy balance. Its action has been studied in animals and obese subjects. Little is known about leptin's role during negative energy balance. OBJECTIVE: The objective was to evaluate the relation between energy turnover, body composition, and plasma leptin concentrations in anorexia nervosa (AN). DESIGN: Sixteen weight-stable women with AN were compared with 22 control subjects and 14 rehabilitated AN patients (R-AN). Basal metabolic rate (BMR) was measured by indirect calorimetry; fat-free mass (FFM) and fat mass (FM) were calculated according to a 4-compartment model. Plasma leptin was determined by radioimmunoassay. RESULTS: The BMR of AN patients (2.73 +/- 0.37 kJ/min) was significantly lower than that of control subjects (3.45 +/- 0.34 kJ/min) (P < 0.001), even after adjustment for FFM (2.92 +/- 0.33 kJ/min in AN patients and 3.30 +/- 0.26 kJ/min in control subjects; P < 0.004). Plasma leptin concentrations in AN patients were 76% lower than in control subjects, even after body fat was controlled for. In R-AN patients, BMR was not significantly different from that of control subjects and leptin concentrations were generally close to normal. Plasma leptin concentrations correlated significantly with FM (r(2) = 0.53, P < 0.0000) and BMR, even after adjustment for FFM (r(2) = 0.21, P < 0.0003). CONCLUSIONS: BMR and plasma leptin concentrations are depressed in patients with AN; this is not explained by body-composition changes. The relation between leptin and BMR suggests that leptin plays a role in the energy sparing response to exposure to chronic energy deficiency. The return of BMR to normal and the significant increase in leptin concentrations in R-AN patients suggests a full reversibility of this adaptation mechanism.     

Glucose and Insulin Responses to a New Zero-Energy Fiber Source

Objective: Consumption of a number of soluble fiber sources reduces glucose and insulin responses in humans. These fibers provide some available energy. Z-trim, a completely insoluble, noncaloric fiber/fat replacer produced from grain, was developed by ARS scientist George Inglett but until this report had not been tested in humans. The objective was to test the effects of consumption of various doses of this new fiber on glucose and insulin responses in humans.

Design: Men and women (12 each) matched for age and body mass index (41 years, BMI 27) were given glucose or glucose with three levels of fiber in a Latin-square design. Blood samples were obtained before and 30, 60, 120 and 180 minutes after solutions containing glucose alone (1 g/kg body weight) and glucose plus 0.08, 0.17 and 0.33 g/kg body weight of Z-trim were consumed. Plasma glucose, insulin and glucagon were determined by enzyme or radioimmunoassays. A repeated-measures analysis of variance was conducted.

Results: Glucose responses were lower for women than for men (p = 0.02) regardless of the test solution. At 30 minutes, glucose levels of men were 0.7–1.1 mmol/L lower after the two higher levels of fiber than after glucose alone. Insulin peak responses were delayed by high amounts of Z-trim. Fasting and response levels of glucagon were higher (p < 0.002) in women than in men. The decline in glucagon usually seen after a glucose load was moderated by the addition of fiber.

Conclusion: Although high levels of this new fiber may beneficially affect glucose metabolism of middle-aged people, it is less effective than soluble fiber.     

Metabolic rate and substrate oxidation of young males with obesity at the different sleep stages

ObjectiveInsufficient and poor-quality sleep among young adults is closely related to obesity and may impact metabolic processes. The mobilization and use of endogenous substrates during sleep, especially fat oxidation, is essential for energy metabolism. This study investigated whether there are differences in sleep structure, metabolic rate, substrate oxidation, and the respiratory quotient (RQ) between young males with normal weight and obesity according to sleep stages and overnight sleep.MethodsFifteen young males with normal weight and fifteen with obesity posited electrodes of polysomnography (PSG) and slept in the metabolic chamber for estimation of sleep structure, sleep metabolic rate (SMR), carbohydrate oxidation (CHOO), fat oxidation (FATO), and RQ. Fat-free mass (FFM) was measured by bioelectrical impedance analysis.ResultsThe sleep period time (p = 0.038) and total sleep time (p = 0.032) were significantly shorter in the obesity group than in the normal-weight group. The obesity group also had a longer sleep latency (p = 0.034) and more sleep-turning events (p = 0.018). CHOO/FFM and the RQ were higher in the obesity group while FATO/FFM was significantly higher in the normal-weight group. FATO/FFM was also higher in the normal-weight group in each sleep stage whereas the RQ was higher in the obesity group (p < 0.05).ConclusionsYoung males with obesity showed lower fat oxidation and more dominant carbohydrate-derived fuel oxidation than normal-weight during sleep and experienced shorter sleep periods and total sleep time.     

Hypermetabolism and altered substrate oxidation in HIV-infected patients with lipodystrophy

ObjectiveHuman immunodeficiency virus type 1 (HIV)-associated lipodystrophy syndrome compromises body composition and produces metabolic alterations, such as dyslipidemia and insulin resistance. This study aims to determine whether energy expenditure and substrate oxidation are altered due to human HIV-associated lipodystrophy syndrome.MethodsWe compared energy expenditure and substrate oxidation in 10 HIV-infected men with lipodystrophy syndrome (HIV+LIPO+), 22 HIV-infected men without lipodystrophy syndrome (HIV+LIPO?), and 12 healthy controls. Energy expenditure and substrate oxidation were assessed by indirect calorimetry, and body composition was assessed by dual-energy X-ray absorptiometry. The substrate oxidation assessments were performed during fasting and 30 min after eucaloric breakfast consumption (300 kcal).ResultsThe resting energy expenditure adjusted for lean body mass was significantly higher in the HIV+LIPO+ group than in the healthy controls (P = 0.02). HIV-infected patients had increased carbohydrate oxidation and lower lipid oxidation when compared to the control group (P < 0.05) during fasting conditions. After the consumption of a eucaloric breakfast, there was a significant increase in carbohydrate oxidation only in the HIV+LIPO? and control groups (P < 0.05), but there was no increase in the HIV+LIPO+ group.ConclusionHypermetabolism and alteration in substrate oxidation were observed in the HIV+LIPO+ group.     

Skeletal muscle enzymes as predictors of 24-h energy metabolism in reduced-obese persons

BACKGROUND: Little is known about the effects of weight loss on the relation between skeletal muscle enzymes and energy metabolism. OBJECTIVE: This study was performed retrospectively to investigate the relation between skeletal muscle enzymes and 24-h energy metabolism in obese persons before and after weight loss. DESIGN: Ten women and 9 men [with body mass indexes (in kg/m(2)) > 30] underwent a 15-wk weight-loss program (-700 kcal/d). Body weight and composition, 24-h energy metabolism (whole-body indirect calorimetry), and maximal activities of phosphofructokinase (EC 2.7.1.11), creatine kinase (CK; EC 2.7.3.2), citrate synthase (CS; EC 4.1.3.7), 3-hydroxyacyl-CoA dehydrogenase (HADH; EC 1.1.1.35), and cytochrome-c oxidase (COX; EC 1.9.3.1) were determined from biopsy samples of the vastus lateralis taken before and after weight loss. RESULTS: Before weight loss, fat-free mass (FFM) was the only predictor of 24-h energy expenditure (R(2) = 0.70, P < 0.001), whereas the cumulative variance in sleeping metabolic rate explained by FFM and fat mass (FM) was 83% (P < 0.001). After weight loss, CS (r = 0.45, P = 0.05) and COX (r = 0.65, P < 0.01) were significantly associated with 24-h energy expenditure, whereas CK (r = 0.53, P < 0.05), CS (r = 0.45, P < 0.05), COX (r = 0.64, P < 0.01), and HADH (r = 0.45, P = 0.05) were all significant correlates of sleeping metabolic rate. After weight loss, FFM, FM, and COX explained 84% (P < 0.01) of the variance in 24-h energy expenditure, whereas FFM, FM, and CK all contributed to the cumulative variance in sleeping metabolic rate explained by this model (R(2) = 0.82, P < 0.05). CONCLUSION: Maximal activities of key skeletal muscle enzymes contribute to the variability in 24-h energy metabolism in reduced-obese persons.