The altered fluid distribution in obesity may reflect plasma hypertonicity.

OBJECTIVE: This study explored whether the increased extracellular relative to intracellular fluid (ECF/ICF) ratio in obesity might reflect osmotic effects of elevated plasma solute concentrations. DESIGN: Cross-sectional, epidemiological survey. SETTING AND SUBJECTS: The present analysis used nationally representative data from the Third National Health and Nutrition Examination Survey on community-dwelling adults (aged 40-59 years) in the US without evidence of glucose dysregulation or chronic disease (n=1285). INTERVENTION: Body mass index (BMI) was estimated from measured height and weight. Total body reactance, an index of body fluid distribution, was determined by bioelectrical impedance analysis. Plasma tonicity (the cumulative index of osmotically effective plasma solute) was estimated from plasma glucose, sodium and potassium. Sex-specific relative odds of lower reactance (or=295 mmol/l) associated with overweight (25or=30) were estimated using logistic regression models that controlled for sociodemographic variables, smoking, leisure-time physical activity, total energy intake, serum creatinine, plasma insulin and glucose. Multinomial logistic regression models tested for associations between weight status and specific serum solute. RESULTS: Independent of covariates, in men and women, overweight and obesity were associated with increased odds of lower reactance and hypertonicity. Overweight and obese individuals with lower reactance had significantly higher serum sodium than normal weight individuals. CONCLUSIONS: Elevated plasma solute concentrations are associated with obesity in free-living adults. Physicians and researchers should be alert to a possible link between hypertonicity and obesity. SPONSORSHIP: Grants from the NIH, Nestle Waters.

A proposed method for assessing plasma hypertonicity in vivo.

Indices of plasma hypertonicity, elevated plasma concentrations of solutes that draw fluid out of cells by osmosis, are needed to pursue hypertonicity as a possible risk factor for obesity and chronic disease. This paper proposes a new index that may be more sensitive to mild hypertonicity in vivo at a point in time than traditional measures. The index compares mean corpuscular volume (MCV) estimates from diluted (in solution by automated cell counter) and nondiluted blood (calculated from manual hematocrit, MCV=Hct/RBC*10(6)). A larger Auto vs Manual MCV (>2 fl) in vitro indicates hypertonicity in vivo if the cell counter diluent is isotonic with the threshold for plasma vasopressin (PVP) release and PVP is detectable in plasma (>0.5 pg/ml). To evaluate this principle of concept, hypertonicity was induced by 24-h fluid restriction after a 20 ml/kg water load in four healthy men (20-46 years). Unlike serum and urine indices, the MCV difference-&-PVP index detected hypertonicity in all participants.

Do protein and energy intakes explain long-term changes in body composition?

BACKGROUND: Despite evidence that profiles of protein and energy intake can determine short-term (< 1 y) change in both lean and fat compartments,the role of diet in longer-term, age-related changes in body composition remains unclear. OBJECTIVE: This paper tests for long-term counterparts to the well-established short-term relationships between protein and energy intake and changes in body composition. DESIGN: Using longitudinal data on 608 healthy, non-obese Chinese (50-69 y)from the 1993 and 1997 China Health and Nutrition Surveys, sex-specific regression models were created to determine if 3-day mean protein (%of energy) and energy (kJ) intakes at baseline predicted change in mid arm muscle area (MAMA) and waist circumference (WC). RESULTS: Although sex-specific U-shaped associations were observed,higher energy intakes were associated with greater gain in WC and less loss of MAMA, and higher protein intakes with less loss of MAMA than lower intakes for both sexes, adjusting for baseline age, height, weight, MAMA, WC, smoking status, activity level, income and urban residence. For males, energy intake be low 95%of the Chinese RDA was associated with significantly smaller gains in WC and greater loss of MAMA than energy intake between 95-125% RDA. For both sexes, protein intake be low 10.4% of energy was associated with significantly greater loss of MAMA than intake between 10.4-12.1% of energy. For females, energy intake above 125% RDA was associated with significantly greater gains in body fat than intake between 95-125% RDA. CONCLUSION: The results suggest that diet may play an important role in age-related change in body composition.

Patterns of long-term change in body composition are associated with diet, activity, income and urban residence among older adults in China.

Studies describing patterns of long-term change in body composition are lacking. Using longitudinal data on 608 healthy, nonobese Chinese (aged 50-70 y) from the 1993 and 1997 China Health and Nutrition Surveys, this article describes the prevalence, sociodemographic and lifestyle correlates of patterns of long-term change in midarm muscle area (MAMA) and body fat (waist circumference). All patterns of change (loss, maintenance [Delta < 1.3 cm(2)], or gain of MAMA with concurrent loss, maintenance [Delta < 2 cm(2)] or gain of body fat), were observed for this sample. After controlling for sex, baseline age, urban residence, height, weight, income, MAMA, waist circumference, smoking status, activity level, mean daily energy and protein intakes (from three 24-h recalls), and change in height, it was determined that subjects who lost both arm muscle and body fat were distinguished from subjects who lost arm muscle but gained body fat by lower income and energy intake at baseline. Although protein intakes at baseline did not differ between the groups that lost arm muscle, protein intakes were significantly higher for subjects who gained both muscle and fat. Patterns of change involving gains in arm muscle were associated with increased protein intake, urban residence, as well as moderate or heavy levels of physical activity at baseline. Variation in protein intake, physical activity, and urban residence also differentiated between the groups that gained fat. Patterns of age-related change in body composition appear associated with modifiable variables, including income, urban residence, activity and protein and energy intake.

Energy density, energy intake and weight status in a large free-living sample of Chinese adults: exploring the underlying roles of fat, protein, carbohydrate, fiber and water intakes.

OBJECTIVE: This paper uses observational data to explore what dietary constituents might be responsible for associations between energy density, energy intake and weight status among free-living individuals. DESIGN: Cross-sectional data on 5783 Chinese adults (aged 20-59 y) from the 1991 China Health and Nutrition Surveys were used to test for associations between energy density, energy intake and weight status, controlling for age, sex, height, activity level, smoking status, urban residence and income. Pearson correlation coefficients were calculated to identify nutrient intake correlates of energy density. Replacing energy density with its nutrient correlates (3 day mean estimates of fat, protein, fiber and water intakes) in the models predicting energy intake and overweight status, the independent effects of specific nutrients were investigated. RESULTS: Energy density was positively and significantly associated with energy intake and overweight status. Energy density was significantly correlated with every nutrient examined, although the correlations were weak for most variables except water intake. Only water intake behaved consistently across analyses. It was negatively correlated with energy density, negatively, significantly and independently associated with energy intake as well as overweight status. Despite positive associations with energy intake, fat and protein intake were not significant predictors of overweight status. Fiber intake was strongly and positively associated with overweight status. CONCLUSIONS: Of the nutrients examined, only water intake appeared to explain the effects of energy density on energy intake and overweight status.

Measuring diet quality in china: the INFH-UNC-CH diet quality index.

OBJECTIVE: This paper describes the development and efficacy of a diet quality index (DQI) for China. DESIGN: The Dietary Guidelines for Chinese Residents motivated the selection of 10 DQI components. These components were weighted and assigned cut-offs and point schemes based on the Chinese Food Guide Pagoda, Chinese and/or international dietary reference values. The efficacy of resulting DQI scores was assessed relative to a priori expectations. SUBJECTS: The Chinese DQI was evaluated using cross-sectional 3 day diet record and anthropometric data on 7450 adults from the 1991 China Health and Nutrition Survey. METHODS: For each individual, a DQI total score was calculated as the sum of components, and DQI pattern scores calculated to reflect the underlying composition of diet quality problems. The DQI scores were compared with component scores, food and nutrient intake, weight status and sociodemographic variables. RESULTS: The total DQI score simultaneously represented all component aspects of diet quality as well as micronutrients not explicitly built into the index. The total DQI score was significantly correlated with food and nutrient intakes, BMI, urban residence and income. The DQI pattern scores correlated with DQI components and weight status as expected. CONCLUSIONS: The China DQI captures variation along several components of diet quality, appears sensitive to under- and overnutrition, as well as sociodemographic variables. The China DQI may prove useful for monitoring the nutrition transition and epidemiologic trends in China. SPONSORSHIP: National Institutes of Health (HD 38700 and R01-HD30880) and the Chinese Academy of Preventive Medicine.

Nutrition of elderly people in China.

Cross-sectional data from the 1991 (n = 1657) and 1993 (n = 1773) China Health and Nutrition Surveys were used to describe patterns in the diets, activity levels and body mass index (BMI) of elderly Chinese (aged 60 or older). In 1991 and 1993, the prevalence of low BMI (BMI < 18.5 or BMI < 22.0) exceeded 15%, while the prevalence of high BMI (BMI > 25.0 or BMI > 27.0) ranged between 4% and 24%. The BMI was consistently, positively and significantly associated with urban residence. Urban residence and income were consistently and positively associated with energy from fat and protein intakes, and decreasing physical activity levels. The results suggest that under- and overnutrition coexist among Chinese elders and are differentially distributed across income and urban/rural strata.

Another look at: fuel + O2 --> CO2 + H2O. Developing a water-oriented perspective.

Water plays many vital roles which must be maintained despite constant threat of water stress from the environment. Mechanisms to maintain these roles over the long-term involve intermediates of many metabolic pathways, such as glycerol, sucrose, free amino acids and their derivatives. In addition to viewing metabolic products as intermediates along energy-related pathways, nutrition researchers and epidemiologists should consider them as determinants of intracellular fluid maintenance. Satiety processes, oxidative-fuel selection, hormonal control, and intracellular-signaling processes can all be interpreted in terms of water-oriented metabolism. Water intake and hydration status can vary considerably, and may be inadequate for a sizeable proportion of Western adults. Due to the metabolic adaptations required to compensate for perpetually inadequate water, chronic sub-optimal water intakes may be highly relevant to chronic disease etiology. Preliminary evidence links water-oriented metabolism to obesity, diabetes, cardiovascular disease, hypertension and cancer. Development of a water-oriented perspective may reveal an important new area of research in human nutrition and epidemiology.

The diuretic effects of alcohol and caffeine and total water intake misclassification.

Data from the 1994 USDA nationwide survey (CSFII) on 190 non-smoking males (aged 20-29) were used to propose a method for adjusting total water intake for the diuretic effects of caffeine and alcohol, and evaluate the potential for related misclassification bias. The data were processed on a per meal basis. Under the assumption that subjects were in water balance at the start of the survey day, water losses due to caffeine (1.17 ml/mg caffeine) and alcohol (10 ml/g alcohol) were subtracted from crude intake estimates. If water intake for one meal was inadequate for excretion of the associated osmotic load at 750 mosmol/l, water losses for the subsequent meal were reduced by 32%. Unadjusted and adjusted mean total water intakes differed by 321.5 g. Misclassification appeared worst at higher water intakes. Linear regression models, each with a water intake variable as an independent variable and body mass index as the outcome, were fit to evaluate the potential for alcohol- and caffeine-related misclassification bias. Misclassification resulted in large changes (all >10%) in linear regression estimates of effect. Future studies of water-disease relationships, especially those intending to compare extremes of total water intake, should consider caffeine- and alcohol-related misclassification bias.

How are consumers of low-fat and high-fat diets perceived by those with lower and higher fat intake?

Dietary social stereotypes may hinder dietary change. The aim of this study was to measure stereotypes attributed to consumers of low-fat and high-fat diets, and to investigate if stereotype attribution differed with subjects' fat intake. A sample of 100 subjects completed a 24-h dietary recall for the estimation of macronutrient intake, and then completed a questionnaire which assessed the stereotypes associated with a low-fat and a high-fat diet. The low-fat diet was associated with a "healthy", "slim", "fit" and "sporty" person, who was "intelligent", "middle class" and "female". Conversely, the high-fat diet was associated with an "unhealthy", "overweight", "unfit" and "inactive" person, who was "unintelligent", "working class", "smoking" and "male". Followers of the low-fat diet were seen as "serious" and "highly strung", while followers of the high-fat diet were seen as "fun-loving" and "happy". However, positive stereotypes were the predominant descriptors of consumers of the low-fat diet, while negative stereotypes were the predominant descriptors of consumers of the high-fat diet by both men and women. Older people were more likely to choose negative descriptors for a follower of the low-fat diet. Subjects were grouped according to their own fat intake. A high-fat (>33% fat energy) group selected more positive and negative stereotypes to describe high- and low-fat diet consumers, respectively, than did their low-fat counterparts (<33% fat energy). Choice of "happy" to describe a follower of a high-fat diet had four-fold higher odds for the high-fat group. The social meaning and values associated with food choices require further investigation. Health education may need to redress some of these stereotypes.