Dietary fat and body weight control

The global obesity epidemic has heightened the debate about dietary factors contributing to weight gain. Media stories have promulgated the notion that obesity has increased despite reductions in dietary fat intake. Some have even speculated that lower dietary fat levels may be driving the rapid rise in weight gain within the population. A close examination of the science reveals a different picture and supports the hypothesis that dietary fat, within the context of the total dietary composition consumed by many populations, promotes obesity. Hence, dietary fat control is still an important strategy as part of an overall approach to body weight management in our modern environment. Dietary fat increases the energy density of foods. Abundant evidence from preclinical and clinical studies indicates that fat promotes excess energy intake and positive energy balance. Dietary fat does not promote its own oxidation in the body and is stored efficiently, promoting a positive fat balance. Thus, both the behavioral and metabolic responses to dietary fat increase the probability of positive energy balance and body fat gain. Restoring fat balance when consuming diets rich in fat requires increasing the size of the body fat mass, increasing physical activity, or reducing dietary fat intake. Numerous epidemiologic, preclinical, and controlled clinical studies have shown that body fat is positively associated with dietary fat intake and that dietary fat manipulation leads to appropriate changes in body fat mass. Finally, data from the National Weight Control Registry, a database of >3000 individuals who have successfully maintained a substantial weight loss, indicate that moderating dietary fat intake is a key strategy for long-term management of body weight.     

Body Mass Index,percent body fat,and regional body fat distribution in relation to leptin concentrations in healthy,non-smoking postmenopausal women in a feeding study

Background  

The relationship between BMI and leptin has been studied extensively in the past, but previous reports in postmenopausal women have not been conducted under carefully controlled dietary conditions of weight maintenance using precise measures of body fat distribution. The aim of the present study was to examine the association between serum leptin concentration and adiposity as estimated by BMI and dual energy x-ray absorptiometry (DEXA) measures (percent body fat, central and peripheral fat, and lean mass) in postmenopausal women.     

Comparison of body fat using anthropometry bioelectrical impedance and DEXA in elderly women

Verify correspondence and compare percentage body fat (%BF) estimates by skinfold thickness (SKT), bioelectrical impedance analysis (BIA) and DEXA. Twenty voluntaries women (aged 62-79 yr) were assessed. The body fat was estimated using two different equations of SKT(Jackson (19); Durning and Womersley, (20)), BIA using two-predictions formulas (23) and DEXA. To compare mean values of %BF was used analysis of variance for repeated measures (ANOVA--Bonferroni), the correlation of the inter-method was verified by Pearson correlation coefficients (r), and correspondence between prediction formulas was tested by using the approach by Bland and Altman (25). The %BF assessed by BIA (23) shown poor correlation (r < 0.5) with two SKT equations. The %BF ranged from 31.5 +/- 5.5 to 41.2 +/- 6.1 (mean +/- SD) for Jackson (19) e DEXA, respectively. The analysis of variance shown no significant differences (p > 0.05) between methods and/or equations by BIA (RJL-CompCorp) vs. DC-Jackson (19). There were observed significant differences (p < 0.001) between all comparisons. The correspondence between RJL-CompCorp vs. Deurenberg (23) was good and the same was observed for DEXA vs. Durning and Womersley (20). Although the methods and/or equations used in this study have been commonly utilized to estimate BF in elderly subjects, they neither must be used as a standard method. Each method has limitations and the comparison can be useful for interpretation of results.     

Reported food intake and distribution of body fat: a repeated cross-sectional study

The number of individuals with age-related cognitive impairment is rising dramatically in the UK and globally. There is considerable interest in the general hypothesis that improving the diet of older people may slow the progression of cognitive decline. To date, there has been little attention given to the possible protective role of n-3 long-chain polyunsaturated fatty acids (n-3 LCPs) most commonly found in oily fish, in age-related loss of cognitive function. The main research hypothesis of this study is that an increased dietary intake of n-3 LCPs will have a positive effect on cognitive performance in older people in the UK. To test this hypothesis, a double-blind randomised placebo-controlled trial will be carried out among adults aged 70–79 years in which the intervention arm will receive daily capsules containing n-3 LCP (0.5 g/day docosahexaenoic acid and 0.2 g/day eicosapentaenoic acid) while the placebo arm will receive daily capsules containing olive oil. The main outcome variable assessed at 24 months will be cognitive performance and a second major outcome variable will be retinal function. Retinal function tests are included as the retina is a specifically differentiated neural tissue and therefore represents an accessible window into the functioning of the brain. The overall purpose of this public-health research is to help define a simple and effective dietary intervention aimed at maintaining cognitive and retinal function in later life. This will be the first trial of its kind aiming to slow the decline of cognitive and retinal function in older people by increasing daily dietary intake of n-3 LCPs. The link between cognitive ability, visual function and quality of life among older people suggests that this novel line of research may have considerable public health importance.     

Reported food intake and distribution of body fat: a repeated cross-sectional study

Background  

Body mass, as well as distribution of body fat, are predictors of both diabetes and cardiovascular disease. In Northern Sweden, despite a marked increase in average body mass, prevalence of diabetes was stagnant and myocardial infarctions decreased. A more favourable distribution of body fat is a possible contributing factor.     

Estimation of body fat by DXA and the four compartment model in Mexican youth

The objective of this study was to validate the estimation of body fat (%BF) by DXA (Dual-Energy X-Ray AbsorciomDPX-MD) against the four compartment model (4C) of body composition in 32 Mexican pubertal girls and boys (aged 9-14 y; F=16). The mean of the difference between DXA and 4C model was -3.5 %BF (p=0.171). The limits of agreement (95% = 2 SD) were +5% to -12%BF. The precision of estimated limits of y the confidence intervals were -1.9% to -5.1%BF (P = 0.050). The concordance correlation coefficient was p = 0.85. The test of accuracy for coincidence of slop intercepts between DXA and the 4C model showed no coincidence (p < 0.05). The precision by R2 explained 83% of the variance (SEE, 4.1%). The individual accuracy assess by the total error was 5.6%. The group mean accuracy by two way analysis of variance of body fat did not show interaction between method (DXA-4C model) and separate analysis of gender and overweight. However, there was an effect of method (p = 0.043) in the presence of overweight (p < 0.001). In conclusion, the estimation of percent of body fat by DXA was not precise and accurate in a group of Mexican children. However, results do not limit the utility of DXA for the measurements of body composition and its relation with health outcomes, especially in follow up studies.     

Isolation and identification of the metabolites of 22,25-dideoxyecdysone from cockroach fat body cultures

Hydroxylation and conjugation were the principal pathways of metabolism of 22,25-dideoxyecdysone in cockroach fat body cultures. The major metabolite isolated and identified was the tetrahydroxy steroid 22-deoxyecdysone; other exdysteroids isolated, in order of decreasing quantities, were 22-deoxy-26-hydroxyecdysone, 22,25-dideoxy-26-hydroxyecdysone, and 22-deoxy-20-hydroxyecdysone. Cockroach fat body from late-instar nymphs appears to lack the mechanism for hydroxylating at C-22. Radioanalyses of the material obtained from enzymic hydrolysis of the conjugate fraction showed 65, 15 and 20% of tetraols, pentaols, and unhydrolyzed conjugates respectively, and no 22,25-dideoxyecdysone. An azasteroid and two nonsteroidal amines that effectively inhibit the activity of 22,25-dideoxyecdysone in the cockroach leg regenerate-fat body culture system enhanced the metabolism of 22,25-dideoxyecdysone, decreased the quantity of the pentaol fraction present, and caused an increase or accumulation of the tetraol and conjugate fractions in the fat body culture system.     

Fatty acid composition and glyceride structure of piglet body fat from different sampling sites

Pigs were slaughtered at 16 weeks of age, and fat samples were obtained from outer and inner shoulder, outer and inner loin, and kidney. Fatty acid composition and glyceride type of distribution were determined. Glyceride structure was determined by pancreatic lipase hydrolysis. There were highly significant differences in fatty acid composition between sites. Fatty acids containing less than 18 carbon atoms were preferentially incorporated in the internal positions of the glycerides. The content of saturated fatty acids and fatty acids containing less than 18 carbon atoms at the 2-position of shoulder and loin glycerides was higher than in kidney glycerides. Differences in glyceride types were noted between sites.     

Conjugated linoleic acid and chromium lower body weight and visceral fat mass in high-fat-diet-fed mice

More than half of the U.S. population has a body mass index of 25 kg/m² or more, which classifies them as overweight or obese. Obesity is often associated with comorbidities such as diabetes, cardiovascular diseases, and cancer. CLA and chromium have emerged as major dietary supplements that reduce body weight and fat mass, and increase basal metabolic rate in animal models. However, studies show that CLA induces insulin resistance in mice and in humans, whereas Cr improves insulin sensitivity. Hence, we designed the present study to examine the combined effect of CLA and Cr on body composition and insulin sensitivity in a Balb/c mice (n=10/group) model of high-fat-diet-induced obesity. CLA alone lowered body weight, total body fat mass, and visceral fat mass, the last of which decreased further with the combination of CLA and Cr. This effect was accompanied by decreased serum leptin levels in CLA-fed and CLA+Cr-fed mice, and by higher energy expenditure (EE) and oxygen consumption (OC) in CLA+Cr-fed mice. Serum levels of glucose, insulin, the pro-inflammatory cytokines, tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6), as well as insulin resistance index (IRI), decreased with CLA, whereas CLA and Cr in combination had significant effects on insulin and IL-6 concentrations and IRI. In summary, CLA+Cr decreased body weight and fat mass in high-fat-diet-fed mice, which may be associated with decreased leptin levels and higher EE and OC.     

Detection of goat body fat in ghee by differential thermal analysis1

The differences in the melting diagrams and crystallization patterns of goat body fat and ghee, as determined by differential thermal analysis, provide a basis for the determination of adulteration in cow or buffalo ghee. The new endothermic peak on the melting diagram in samples having more than 10% goat body fat can be used for qualitative detection and the crystallization diagram can be used for quantitative estimation. NDRI (India) Publication No. 79-314.     

Detection of pig and buffalo body fat in cow and buffalo ghees by differential scanning calorimetry

Adding small amounts of pig or buffalo body fat to cow or buffalo ghee results in the appearance of an extra peak located at high temperature in the melting and crystallization curves as determined by the differential scanning calorimetry (DSC) technique. Ghee adulterations with these animal fats at levels down to 5% are clearly seen in the crystallization diagrams. Quantitative measurements can be obtained by this method in the case of adulterations with buffalo body fat. On the other hand, this method does not detect vegetable oils such as coconut oil, and gives similar results for cottonseed-fed buffalo ghee and ghee adulterated with animal body fats.     

Continuous and intermittent exercise: effects of training and detraining on body fat in obese rats

Exercise training is often recommended in prevention and treatment of obesity. The present study was designed to compare the effects of intermittent and continuous exercise on weight loss and carcass composition in obese rats. Obese male Wistar rats (monosodium glutamate [MSG] administration, 4 mg/g of body weight every other day from birth to 14 days old) were used. After drug administration, the rats were separated into three groups: MSG-SED (sedentary), MSG-CONT (continuous, swimming, 45 min/day, 5 days/week, with and overload of 5% body weight for 12 weeks) and MSG-INT (intermittent, 15 s swimming intermitted by 15 s rest, during 45 min, 5 days/week, with and overload of 15% body weight for 12 weeks). Rats of the same age and strain, administered with saline were used as control (SAL), and subdivided into three groups: SAL-SED, SAL-CONT and SAL-INT. The animals were evaluated at the 10 weeks of training and 8 weeks of its interruption. MSG rats showed higher carcass fat as well as weight and cell size in epididymal adipose tissue than SAL rats, indicting the efficacy of the drug in producing obesity. Intermittent training protocol led to a reduction in blood lactate accumulation during acute exercise and both protocols reduced body weight gain during the experiment in MSG rats. After 8 weeks of training interruption no differences were observed among groups in the examined parameters. Only intermittent exercise training improved aerobic fitness but both protocols were similarly efficient in determining weight loss. However, the effects were transitory, since they disappeared after detraining.     

Supplementation with CLA: Isomer incorporation into serum lipids and effect on body fat of women

Animal studies have suggested that CLA, a natural component of meat and dairy products, may confer beneficial effects on health. However, human studies using supplementation with CLA have produced contradictory results. The aim of the present study was to further investigate the effect of CLA supplementation on human body fat, serum leptin, and serum lipids, as well as the incorporation of CLA isomers into serum lipids classes. Sixteen young healthy nonobese sedentary women received 2.1 g of CLA (divided equally between the cis,trans-9,11 and trans,cis-10,12 isomers) daily for 45 d and placebo for 45 d in a randomized double-blind crossover design. Body fat was estimated (by measurement of skinfold thickness at 10 sites), and blood was sampled at the beginning, middle, and end of the entire intervention period; an additional blood sample was obtained 2 wk thereafer. No significant differences in energy, carbohydrate, lipid, or protein intake existed between the CLA and placebo intake periods. No significant differences were found in body fat or serum leptin, TAG, total cholesterol, HDL-cholesterol, and alanine aminotransferase between CLA and placebo. The CLA isomer content of serum TAG, phospholipids, and total lipids increased 2–5 times with CLA supplementation (P<0.05). In contrast, the CLA content of cholesteryl esters did not change significantly. The period of 2 wk after the end of CLA supplementation was sufficient for its washout from serum lipids. These data indicate that supplementation with 2.1 g of CLA daily for 45 d increased its levels in blood but had no effect on body composition or the lipidemic profile of nonobese women.     

Validity of an equation based on anthropometry to estimate body fat in older adults

A prediction equation to estimate body fat mass from skinfold thickness for healthy elderly was developed using a four compartmental (4C) model as criterion method. This study included 202 subjects = 60 y old. The measurements of total body water, bone mineral content and body density were included in the 4C model equation. Total sample was randomly partitioned. Sub-sample one was used to design the equations, which were applied in sub-sample two. Its accuracy and precision was evaluated by lineal regression analysis and the bias by Bland and Altman analysis and simple lineal regression. The best model included body mass, sex and the calf and triceps skinfolds thicknesses, with an R2, standard error of the estimate and Cp of 0.85, 3.2 and 3.2, respectively. When the equation was applied in sub-sample two, it was accurate and precise, it showed no significant deviation from the line of identity (the intercept was no significantly different from zero, P>0.05), and slope was different from cero (or similar to 1) (P<0.05). Fat mass by the equation accounted for 86% of the variability of the mean fat mass estimated by the 4C model, having a low standard error of the estimate (3.2 kg) and low pure error (3.1 kg). The new equation was accurate and precise as well as free of significant bias in men and women together and for separately. This equation can be a good option to estimate fat mass in elderly men and women with similar physical characteristics to subjects of this study, and it can be used in clinical and epidemiological studies in this growing group.     

健康发展

“十一五”开局之年,中国橡胶工业经济运行由高速增长走向稳步、快速增长,呈现更加健康的发展态势。轮胎子午化率达到67.1%,比上年提高5.4个百分点。全钢子午胎产量3255万条,比上年递增33.5%,增幅比上年回落11个百分点。大企业集团集中度明显提高,产量居前10名的企业子午胎产量占子午胎总产量的77%以上。出口轮胎产品结构调整效应明显,子午胎出口交货量6292.5万条,占出口总量的77.16%。据测算,全国橡胶行业2006年度生胶消耗量可达到449万～454万吨。这是从中国橡胶工业协会发布的《2006年度橡胶行业经济运行状况通报》中获得的信息。详见本期“协会视窗”。