Critical analysis of bariatric procedures in Prader-Willi syndrome.

Prader-Willi syndrome (PWS) is a complex genetic disorder localized to chromosome 15 and is considered the most common genetic cause of the development of life-threatening obesity. Although some morbidities associated with PWS, including respiratory disturbance/hypoventilation, diabetes, and stroke, are commonly seen in obesity, others such as osteoporosis, growth hormone deficiency, and hypogonadism, and also altered pain threshold and inability to vomit, pose unique issues. Various bariatric procedures have been used to cause gastric stasis, decrease gastric volume, and induce malabsorption, with poor results in PWS patients in comparison with normal obese individuals.

A high protein, low calorie liquid diet in the treatment of very obese adolescents: long-term effect on lean body mass.

The use of Optifast-70, a high protein liquid diet, when used in the range of 500 to 700 cal over 5 months in very obese adolescents, was associated with weight loss of 20 to 25% of initial weight of which 70 to 75% of the loss was due to fat. No significant side effects were noted. Twenty-four hour electrocardiographic monitoring showed no significant changes, and linear growth continued. Lean body mass loss was 36% of the weight lost during the first 5 wks, but was only 10% of the weight lost during the next few months. Two adolescent males had negative phosphorus and nitrogen balances over the first 4 wk, implying that males may have slightly higher phosphorus, nitrogen, and calorie requirements.

Growth and nutritional status of Bedouin infants in the Negev Desert, Israel: evidence for marked stunting in the presence of only mild malnutrition.

Growth and feeding practices of 353 Bedouin infants from the Negev Desert, Israel, were compared to those of 302 Jewish infants from the same area and to American standards. These two populations differed in their cultures and educational backgrounds. The use of medical and health services was lower among the Bedouin population. The feeding practices of the Bedouin infants were markedly different from those of their controls. The Bedouin infants show a progressive decrease in weight, length, and head circumference (means of all three parameters were around the 5th percentile) while the Jews were comparable to Americans. The nutritional status was assessed by three different anthropometric measurements. The weight to length ratio showed that 88% of Bedouin and 96% of Jewish infants were above the 10th percentile. Tricep skinfold measurements showed that 96% of the Bedouins and 99% of the Jews were above the 5th percentile. The midarm circumference to head circumference ratio was in the range between 0.280 and 0.310 (mild malnutrition range) while that of the Jews was above 0.310 (well-nourished range). These data show marked stunting in the presence of only mild malnutrition. This observation argues against the general belief that marked stunting is the result of prolonged severe malnutrition. Differences in cultural and genetic backgrounds, as well as different feeding practices and increased morbidity, could contribute to this phenomenon.

PIP: Growth and feeding practices of 353 Bedouin infants from the Negev Desert in Israel were compared to those of 302 Jewish infants from the same area and to American standards. These 2 populations differed in their cultures and educational backgrounds. The use of medical and health services was lower among the Bedouin population. Feeding practices of the Bedouin infants were markedly different from those of their controls. The Bedouin infants show a progressive decrease in weight, length, and head circumference (mean of all 3 parameters was around 5th percentile) while the Jewish children were comparable to Americans. The nutritional status was assessed by 3 different anthropometric measurements. The weight-to-length ratio showed that 88% of Bedouin and 96% of Jewish infants were above the 10th percentile. Tricep skinfold measurements showed that 96% of the Bedouin and 99% of the Jews were above the 5th percentile. The midarm circumference-to-head-circumference ratio was in the range between 0.280-0.310 (mild malnutrition range) while that of the Jews was above 0.310 (well-nourished range). These data show marked stunting in the presense of only mild malnutrition. This observation argues against the general belief that marked stunting is the result of prolonged severe malnutrition. Differences in cultrual and genetic backgrounds as well as different feeding practices and increased morbidity could contribute to this phenomenon.

Reduced renal acid excretion in malnutrition: a result of phosphate depletion.

Eleven infants recovering from protein-calorie malnutrition secondary to acquired monosaccharide intolerance were found to have reduced plasma bicarbonate concentration associated with inadequate weight gain. Renal net acid excretion (NAE) was decreased to a mean of 34.2 micronEq/1.73m2/min. Titratable acidity (TA) was markedly reduced, accounting for only 16% of NAE. This marked reduction in TA was associated with reduced mean phosphate (PO4) excretion (.074 mg/min) and a reduced mean serum PO4 (3.9 mg/dl), suggesting PO4 depletion. Two patients received intravenous phosphate loads, resulting in an increase in mean NAE from 35.1 to 89.7 microgEq/1.73m2/min. A similar response was seen after oral PO4 supplementation. Three patients were studied after partial correction of their acidosis. At a relatively low plasma bicarbonate concentration (mean = 16.6 mmoles/liter) significant amounts of bicarbonate were detected in the urine (mean = 8.7 micronEq/1.73m2/min), suggesting a defect in bicarbonate reabsorption. Five patients studied after complete recovery from malnutrition had normal NAE in response to ammonium chloride load. The reduction in NAE appears to be secondary to unavailability of urinary buffers and a reduction in bicarbonate reabsorption; both of these defects can be explained by phosphate depletion.

Reliability of fat-free mass estimates derived from total-body electrical conductivity measurements as influenced by changes in extracellular fluid volume.

Our study addresses the concern that the relationship between total-body electrical conductivity (TOBEC) measurements and the fat-free mass (FFM) or total-body water (TBW) of an individual is altered if significant fluid and electrolyte changes occur. Body composition and TOBEC measurements were obtained from 11 healthy miniature piglets before and after an intraperitoneal injection of physiological saline. The procedure expanded the extracellular fluid (ECF) volume by 11.8-34.1%, which represented an average increase in TBW of 7.9%. The linear regressions that related the preinjection and postinjection estimates of TBW or FFM to the corresponding transformed TOBEC signals were the same. Thus, the prediction equations derived for the untreated piglets accurately predicted both TBW and FFM in the piglets whose volume was expanded. These data suggest that prediction equations derived from healthy subjects should be equally valid for subjects with altered fluid status.

In vivo isotope-fractionation factors and the measurement of deuterium- and oxygen-18-dilution spaces from plasma, urine, saliva, respiratory water vapor, and carbon dioxide.

In vivo isotope-fractionation factors were determined for hydrogen and oxygen between plasma water samples and samples of urine, saliva, respiratory water vapor, and carbon dioxide in 20 normal adults. The isotope-fractionation factors ranged from 0.944 to 1.039 for 2H in breath water vapor and for 18O in breath CO2, respectively. When corrected for isotope fractionation, the 2H- and 18O-dilution spaces determined from urine, saliva, respiratory water, and CO2 were within -0.10 +/- 1.09 kg (mean +/- SD, n = 60) and 0.04 +/- 0.68 kg (n = 80), respectively, of the values determined from plasma. In the absence of these corrections, we observed a 6% overestimation of 2H-dilution space and a 1% overestimation of 18O-dilution space from the use of respiratory water values. A 4% underestimation of the 18O-dilution space was observed for breath CO2 without correction for isotope fractionation.

Total body water estimated by measuring total-body electrical conductivity.

A second-generation total-body electrical conductivity (TOBEC) instrument for adults (HA-2) was evaluated against isotope dilution of 2H and 18O for its ability to estimate total body water (TBW) in 20 healthy adults. The highest correlation coefficient (0.997) and the lowest standard error of the estimate (0.68 kg) were obtained using the first (FC0) and third (FC2) Fourier coefficients of the transformed TOBEC signals and the variables height (m) times average lean circumference (m) and age (y) in the prediction equation of TBW as follows: TBW (H218O) in kg = 10.8 + (0.0724.FC0) - (0.221.FC2) + (0.0398.age) + (9.2.height.average lean circumference) where average lean circumference is the average of the lean chest, abdomen, and thigh circumferences. The TOBEC instrument for adults provides a suitable alternative for the estimation of TBW.

Proximal muscle weakness and selenium deficiency associated with long term parenteral nutrition.

A 33-yr-old white female with short bowel syndrome secondary to trauma was maintained on home parenteral nutrition for 4 yr when her plasma, red cell, white cell, and platelet glutathione peroxidase (GSHPx) activities were found to be extremely low, as were her plasma and red cell selenium levels. During her first year on parenteral nutrition she noted the onset of an inability to rise from a squatting position, rapid tiring when stair climbing, and weakness when attempting to lift large or moderately heavy objects. Treatment with 400 micrograms/d of selenious acid intravenously was associated with a disappearance of her symptoms and an increase in proximal muscle strength within 6 wk. The plasma and red cell selenium levels, and the plasma and white cell GSHPx activities rose to normal levels within 6 wk. Red cell GSHPx activity returned to normal by 3 mo.

Energy metabolism, nitrogen balance, and substrate utilization in critically ill children.

BACKGROUND: Critically ill patients are characterized by a hypermetabolic state, a catabolic response, higher nutritional needs, and a decreased capacity for utilization of parenteral substrate. OBJECTIVE: We sought to analyze the relation between a patient's metabolic state and their nutritional intake, substrate utilization, and nitrogen balance (NB) in mechanically ventilated, critically ill children receiving parenteral nutrition. DESIGN: This was a cross-sectional study in which resting energy expenditure (REE) and NB were measured and substrate utilization and the metabolic index (MI) ratio (REE/expected energy requirements) were calculated. RESULTS: Thirty-three children (mean age: 5 y) participated. Their average REE was 0.23 +/- 0.10 MJ x kg(-1) x d(-1) and their average MI was 1.2 +/- 0.5. Mean energy intake, protein intake, and NB were 0.25 +/- 0.14 MJ x kg(-1) x d(-1), 2.1 +/- 1 g x kg(-1) x d(-1), and -89 +/- 166 mg x kg(-1) x d(-1), respectively. Patients with an MI >1.1 (n = 19) had a higher fat oxidation than did patients with an MI <1.1 (n = 14; P < 0.05). Patients with lipogenesis (n = 13) had a higher carbohydrate intake than did patients without lipogenesis (n = 20; P < 0.05). Patients with a positive NB (n = 12) had a higher protein intake than did patients with a negative NB (n = 21; P < 0.001) and lower protein oxidation (P < 0.01). CONCLUSIONS: Critically ill children are hypermetabolic and in negative NB. In this population, fat is used preferentially for oxidation and carbohydrate is utilized poorly. A high carbohydrate intake was associated with lipogenesis and less fat oxidation, a negative NB was associated with high oxidation rates for protein, and a high protein intake was associated with a positive NB.

Resting energy expenditure in children in a pediatric intensive care unit: comparison of Harris-Benedict and Talbot predictions with indirect calorimetry values.

The use of prediction equations has been recommended for calculating energy expenditure. We evaluated two equations that predict energy expenditure, each of which were corrected for two different stress factors, and compared the values obtained with those calculated by indirect calorimetry. The subjects were 55 critically ill children on mechanical ventilation. Basal metabolic rates were calculated with the Harris-Benedict and Talbot methods. Measured resting energy expenditure was 4.72 +/- 2.53 MJ/d. The average difference between measured resting energy expenditure and the Harris-Benedict prediction with a stress factor of 1.5 was -0.98 MJ/d, with an SD delta of 1.56 MJ/d and limits of agreement from -4.12 to 2.15; for a stress factor of 1.3 the average difference was -0.22 MJ/d, with an SD delta of 1.57 MJ/d and limits of agreement from -3.37 to 2.93. The average difference between measured resting energy expenditure and the Talbot prediction with a stress factor of 1.5 was -0.23 MJ/d, with an SD delta of 1.36 MJ/d and limits of agreement from -2.95 to 2.48; for a stress factor of 1.3, it was 0.42 MJ/d, with an SD delta of 1.24 MJ/d and limits of agreement from -2.04 to 2.92. These limits of agreement indicate large differences in energy expenditure between the measured value and the prediction estimated for some patients. Therefore, neither the Harris-Benedict nor the Talbot method will predict resting energy expenditure with acceptable precision for clinical use. Indirect calorimetry appears to be the only useful way of determining resting energy expenditure in these patients.

Effect of breast-feeding on morbidity in rotavirus gastroenteritis.

Fifty infants less than 1 year of age with rotavirus gastroenteritis were studied with regard to the protective effect of breast-feeding. The initial incidence of breast-feeding was 64% in the patients infected with rotavirus and 70% in a matched control population. Seven patients were breast-fed at the time of infection, 25 patients had stopped breast-feeding prior to infection, and 18 patients were exclusively formula-fed. There were no significant differences between groups in the average age of infection, mean duration of diarrhea, mean number of bowel movements in 24 hours, or in the frequency of fever or irritability. The only apparent difference between groups was that the frequency of vomiting was significantly decreased in the breast-fed children. The results of this study suggest that breast-feeding offers little protection against rotavirus gastroenteritis.

Anthropometric measurements and estimating body composition in ballet dancers.

The purpose of this study was to develop and cross-validate an equation for estimating fat-free mass (FFM) in female ballet dancers. One hundred twelve, 11- to 25-yr old, female dancers had FFM measured by total body electrical conductivity (TOBEC) and anthropometrics, including skinfold and circumference measurements. The regression equation that best estimated FFM in the dancers was FFM = 0.73 x body weight (kg) + 3.0, (R2 = 88%, SEE = 1.5 kg, P < 0.001). This equation was then cross-validated on a separate group of 23 female dancers who also had FFM measured by TOBEC. FFM estimated by this equation correlated with FFM measured by TOBEC (r = 0.94, SEE = 0.9 kg), and the difference in the FFM values using the two methods (the equation and TOBEC) did not change with the size of the FFM of the dancers. FFM in accomplished female ballet dancers can be best estimated from body weight alone. This is related to the homogeneity of body size and body composition in female ballet dancers at this level.

Body composition in ballet dancers measured by total body electrical conductivity.

The purpose of this study was to describe the body composition of adolescent and young adult ballet dancers using total body electrical conductivity (TOBEC). We studied 112 female and 33 male dancers. The mean ages were 15.0 +/- 2.0 and 18.7 +/- 3.1 yr for females and males, respectively. The mean percent body fat (PBF) values were 20.1 +/- 3.6% for the females and 14.5 +/- 4.2% for the males. Age and pubertal development were not significantly related to PBF in the females. Age and pubertal status were significantly inversely related to PBF in the males. There was no difference in dance history, percent body fat, and abdominal/hip or waist/hip ratios in eumenorrheic vs amenorrheic dancers. Estimated calorie intake indicated that dancers with menstrual abnormalities had lower calorie intake than those with normal menses. This is the largest group of ballet dancers whose body composition has been studied. Our PBF measurements are higher than in previous reports using hydrodensitometry, which may have underestimated body fat by not accounting for the increased bone density in the lower extremities of dancers. Our data suggest that previous measurements of PBF in dancers are underestimates; these new data challenge our concept of PBF values in dancers.

Total body water and fat-free mass in ballet dancers: comparing isotope dilution and TOBEC.

Nine male and seven female high level ballet students had total body water (TBW) measured by two methods: 1) H2(18)O isotope dilution and 2) total body electrical conductivity (TOBEC). TBW from TOBEC measurements was calculated using an equation previously derived from adults, and these new measurements correlated highly with TBW by isotope dilution (r = 0.99, SEE = 0.78 kg). However, the difference between these two methods increased as TBW increased. Therefore, a new equation (ballet equation) was developed which improved the prediction of TBW for individuals (SEE = 0.69 kg) and for which the difference in TBW between isotope dilution and TOBEC was independent of the TBW value. Using age-adjusted hydration constants, the TBW measurements by isotope dilution were converted to fat-free mass, and these values were used to develop an accurate equation for predicting fat-free mass from TOBEC measurements (r = 0.99, SEE = 0.91 kg). In addition, we measured TBW and calculated FFM in ten control adolescents and used these values to develop equations for predicting TBW (r = 0.99, SEE = 1.01 kg) and FFM (r = 0.99, SEE = 1.42 kg) in a combined group of adolescent dancers and non-dancers. Total body water and fat-free mass can be accurately measured in adolescent ballet dancers and non-dancers using TOBEC.

Body fat in normal adults estimated by oxygen-18- and deuterium-dilution and by anthropometry: a comparison.

We estimated body fat in 20 normal adults (10 males and 10 females) from 18O- and 2H-dilution spaces and from the equations of Durnin & Womersley and Pollock, Schmidt & Jackson based on skinfold thickness measurements. Differences between methods for body fat estimation were found to be sex-dependent: subsequent analyses indicated significant differences between methods within each sex. Regardless of sex, the highest fat estimates were obtained with the 18O-dilution method, followed by those obtained with the 2H-dilution method or the Durnin & Womersley equation. The lowest fat estimates were obtained using the Pollock, Schmidt & Jackson equation. The 18O-dilution method and the Durnin & Wormersley anthropometric method are both suitable and appropriate for body fat estimation in adults studied under field conditions.

Resting energy expenditure and nitrogen balance in critically ill pediatric patients on mechanical ventilation.

Nutritional support is important in critically ill patients, with variable energy and nitrogen requirements (e.g., sepsis, trauma, postsurgical state) in this population. This study investigates how age, severity of illness, and mechanical ventilation are related to resting energy expenditure (REE) and nitrogen balance. Nineteen critically ill children (mean age, 8 +/- 6 [SD] y and range 0.4-17.0 y) receiving total parenteral nutrition (TPN) were enrolled. We used indirect calorimetry to measure REE. Expected energy requirements (EER) were obtained from Talbot tables. Pediatric Risk of Mortality (PRISM) and Therapeutic Intervention Scoring System (TISS) score were calculated. Total urinary nitrogen was measured using the Kjeldahl method. PRISM and TISS scores were 9 +/- 5 and 31 +/- 6 points, respectively. REE was 62 +/- 25 kcal.kg-1.d-1, EER was 42 +/- 11 kcal.kg-1. d-1, and caloric intake was 49 +/- 22 kcal.kg-1.d-1. Nitrogen intake was 279 +/- 125 mg.kg-1.d-1, total urinary nitrogen was 324 +/- 133 mg.kg-1.d-1, and nitrogen balance was -120 +/- 153 mg.kg-1.d-1. The protein requirement in this population was approximately 2.8 g.kg-1.d-1. These critically ill children were hypermetabolic, with REE 48% higher (20 kcal.kg-1.d-1) than expected. Nitrogen balance significantly correlated with caloric and protein intake, urinary nitrogen, and age, but not with severity of illness scores or ventilatory parameters.

A comparison of fat-free mass estimates in men infected with the human immunodeficiency virus.

BACKGROUND: Loss of lean-body mass has been found to be predictive of death from wasting in HIV-infected individuals. Several clinically applicable, noninvasive methods for estimating body wasting are available, but the comparability of these methods is not known. The objective of this study was to assess the agreement between estimates of lean-body mass in HIV-infected men. METHODS: Lean-body mass was measured by bioelectrical impedance assessment, by prediction equations that used anthropometric measurements, and by total body electrical conductivity as the comparison method in 27 outpatient HIV-infected men seen at the Houston Veterans Affairs Special Medicine Clinic. Agreement was assessed by comparing the difference between two methods (the bias) with the mean of those two methods. This statistical approach evaluates whether two methods are similar enough that measurements from one might accurately replace those of the other. RESULTS: The mean +/- SE for lean-body mass were 55.98 +/- 1.96 kg for total body electrical conductivity and 55.18 +/- 1.27 kg for bioelectrical impedance assessment; they ranged from 55.18 +/- 1.27 to 63.71 +/- 1.89 kg for the prediction equations. CONCLUSIONS: In individual subjects, no alternate method gave estimates of lean-body mass that were the same as estimates from total body electrical conductivity. One prediction equation (Brozek) gave estimates that might be useful for following changes in fat-free mass over time because the bias did not change substantially for increasing values of lean-body mass. On the other hand, because there were no statistically significant differences between the mean lean-body mass estimates by total body electrical conductivity and those measured by bioelectrical impedance assessment or a prediction equation on the basis of body mass index, the latter two methods might be useful in assessing lean-body mass in groups.

Body composition in adolescent athletes.

This article has set out to provide basic knowledge about body composition in athletic and nonathletic adolescents and young adults and to provide the practicing physician with methods of making body composition assessment. We suggest the physician approach the adolescent athlete who requests information about body composition in the following way: 1. Calculate the ideal body weight. 2. Estimate the percentage of body fat, realizing the errors associated with each method. If a body composition laboratory is available, use that equipment. In the absence of this equipment, we recommend the equations of Slaughter et al, given earlier. 3. The athlete should be given a range of percentage of body fat values measured in other athletes of the same gender and sport. Health and performance should be monitored as the athlete attempts to achieve or maintain body composition in this range. 4. If the athlete has an interest in altering body composition, then recommend the athlete seek the advice of a professional who has expertise in nutrition and physiology.

Total body electrical conductivity measurements in the neonate.

TOBEC measurements are based on the premise that a conductive object will interact with an electromagnetic field and result in the dissipation of a small quantity of the field's energy. TOBEC instruments provide a measure of this energy loss, which for a given conductor varies according to its size. The conductive component of the body is that part that contains water with dissolved electrolytes, i.e., essentially the FFM. Fat, by definition, is anhydrous and does not contribute to a TOBEC measurement. To interpret TOBEC readings in terms of the quantity of FFM in the body requires the use of a calibration equation that is generated by measuring the FFM of a reference population using an alternative technique and relating this to each individual's TOBEC value. Because no alternative method exists to estimate the FFM of an infant, a calibration equation is used that was generated from measurements of young miniature piglets. The body composition of infants thus derived is consistent with our general understanding of the changes in fat and FFM in human infants in early life. Whether TOBEC can be used as described in premature or older children has yet to be determined. Variations in the composition of the FFM do not seem to compromise the accuracy of the technique. TOBEC measurements are precise, rapid, noninvasive, and safe and cause the subject no discomfort. These features not only make TOBEC a useful tool for the nutritional assessment of a pediatric patient but they also may be a useful diagnostic tool for the clinician.

Intestinal strictures presenting with gastrointestinal blood loss.

The typical manifestations of intestinal strictures include abdominal distention, bilious vomiting, hematochezia, diarrhea, disaccharide intolerance, and occasional growth failure. However, chronic gastrointestinal (GI) blood loss from ulcers at the site of the stricture has not been noted as a major feature. We report three patients in whom an intestinal stricture presented with minimal evidence of obstruction, but with GI bleeding and anemia. Our experience indicates that intestinal strictures with ulcers must be considered in the differential diagnosis of blood loss, and that surgical intervention may be required if GI blood loss is chronic and laboratory results are negative.