Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Plant-derived polyunsaturated fatty acids and markers of glucose metabolism and insulin resistance : A meta-analysis of randomized controlled feeding trials
    Wanders, Anne J. ; Blom, Wendy A.M. ; Zock, Peter L. ; Geleijnse, Johanna M. ; Brouwer, Ingeborg A. ; Alssema, Marjan - \ 2019
    BMJ Open Diabetes Research and Care 7 (2019)1. - ISSN 2052-4897
    dietary fat - glucose metabolism - insulin resistance - Linoleic acid - meta-analysis

    The objective of this meta-analysis was to investigate the effects of plant-derived polyunsaturated fatty acids (PUFAs) on glucose metabolism and insulin resistance. Scopus and PubMed databases were searched until January 2018. Eligible studies were randomized controlled feeding trials that investigated the effects of a diet high in plant-derived PUFA as compared with saturated fatty acids (SFA) or carbohydrates and measured markers of glucose metabolism and insulin resistance as outcomes. Data from 13 relevant studies (19 comparisons of plant-derived PUFA with control) were retrieved. Plant-derived PUFA did not significantly affect fasting glucose (-0.01 mmol/L (95 % CI - 0.06 to 0.03 mmol/L)), but lowered fasting insulin by 2.6 pmol/L (-4.9 to -0.2 pmol/L) and homeostatic model assessment-insulin resistance (HOMA-IR) by 0.12 units (-0.23 to - 0.01 units). In dose-response analyses, a 5% increase in energy (En%) from PUFA significantly reduced insulin by 5.8 pmol/L (95% CI -10.2 to -1.3 pmol/L), but not glucose (change -0.07, 95% CI -0.17 to 0.04 mmol/L) and HOMA-IR (change - 0.24, 95% CI -0.56 to 0.07 units). In subgroup analyses, studies with higher PUFA dose (upper tertiles) reduced insulin (-6.7, -10.5 to -2.9 pmol/L) and HOMA-IR (-0.28, -0.45 to -0.12 units), but not glucose (-0.09, 95% CI -0.18 to 0.01 mmol/L), as compared with an isocaloric control. Subgroup analyses showed no differences in effects between SFA and carbohydrates as replacement nutrients (p interaction ≥0.05). Evidence from randomized controlled trials indicated that plant-derived PUFA as an isocaloric replacement for SFA or carbohydrates probably reduces fasting insulin and HOMA-IR in populations without diabetes.

    The evaluation of energy in fish feed
    Haidar, Mahmoud - \ 2017
    Wageningen University. Promotor(en): J.A.J. Verreth, co-promotor(en): J.W. Schrama. - Wageningen : Wageningen University - ISBN 9789463438049 - 155
    oreochromis niloticus - fish feeding - feed formulation - digestible energy - dietary protein - dietary fat - carbohydrates - growth - feed evaluation - fish culture - aquaculture - oreochromis niloticus - visvoeding - voersamenstelling - verteerbare energie - voedingseiwit - voedingsvet - koolhydraten - groei - voederwaardering - visteelt - aquacultuur

    New and alternative plant ingredients are increasingly incorporated in fish feed due to the scarcity of captured fish and increased fishmeal and fish oil prices. As a result, current fish feeds are characterized by a highly variable ingredients composition, leading to a similar variability in the dietary macronutrients composition, especially the carbohydrates fraction. Appropriate formulation of the energy component in fish feeds requires information on nutrient digestibility, energy requirements for maintenance, and the efficiency of utilization of digestible energy for growth (kgDE). In fish feed formulation, the energy evaluation is based on digestible energy (DE) basis. The main assumptions of this DE system are that maintenance requirements and kgDE are independent of dietary factors. The main objective of this thesis was to evaluate and improve the DE system for Nile tilapia. Data showed that, opposite to what is assumed in literature and irrespective of the feeding level applied, an optimal digestible protein to digestible energy ratio (DP/DE) for young Nile tilapia could not be detected. In addition, it was expected that Nile tilapia would show a maximal protein deposition in relation to a wide range of DP/DE ratios, however, this was either observed. Further investigations showed that different body compartments/organs responded differently in terms of protein and fat composition as a result of changes in the dietary DP/DE ratio. In tilapia, viscera and the “rest” fraction (head, skin, fins and bones) were the main site for fat retention. In addition, protein content of fillets seems to be constant (about 17%) and not affected by dietary factors in Nile tilapia. In addition, the effect of using new plant ingredients in Nile tilapia diets was also investigated. The results showed that the ingredients composition had an effect on the maintenance requirements of Nile tilapia. Further, changes in the ratio of starch vs non starch carbohydrates revealed that energy retention was lower when more dietary fibers were included. In addition, the net energy retention differed also when the levels of digestible protein, fat and carbohydrates changed in the diets. The latter results proved that kgDE was not constant and was dependent on diet composition. All aforementioned results led us to calculate the energetic efficiencies of digestible protein, fat and carbohydrates for net energy retention. These estimated efficiencies were used to propose a net energy evaluation system being feasible for Nile tilapia.

    Diet density during the first week of life: Effects on energy and nitrogen balance characteristics of broiler chickens
    Lamot, D.M. ; Sapkota, D. ; Wijtten, P.J.A. ; Anker-Hensen, I. van den; Heetkamp, M.J.W. ; Kemp, B. ; Brand, H. van den - \ 2017
    Poultry Science 96 (2017)7. - ISSN 0032-5791 - p. 2294 - 2300.
    broiler chickens - dietary fat - diet density - energy balance - indirect calorimetry
    This study aimed to determine effects of diet density on growth performance, energy balance, and nitrogen (N) balance characteristics of broiler chickens during the first wk of life. Effects of diet density were studied using a dose-response design consisting of 5 dietary fat levels (3.5, 7.0, 10.5, 14.0, and 17.5%). The relative difference in dietary energy level was used to increase amino acid levels, mineral levels, and the premix inclusion level at the same ratio. Chickens were housed in open-circuit climate respiration chambers from d 0 to 7 after hatch. Body weight was measured on d 0 and 7, whereas feed intake was determined daily. For calculation of energy balances, O2 and CO2 exchange were measured continuously and all excreta from d 0 to 7 was collected and analyzed at d 7. Average daily gain (ADG) and average daily feed intake (ADFI) decreased linearly (P = 0.047 and P < 0.001, respectively), whereas gain to feed ratio increased (P < 0.001) with increasing diet density. Gross energy (GE) intake and metabolizable energy (ME) intake were not affected by diet density, but the ratio between ME and GE intake decreased linearly with increasing diet density (P = 0.006). Fat, N, and GE efficiencies (expressed as gain per unit of nutrient intake), heat production, and respiratory exchange ratio (CO2 to O2 ratio) decreased linearly (P < 0.001) as diet density increased. Energy retention, N intake, and N retention were not affected by diet density. We conclude that a higher diet density in the first wk of life of broiler chickens did not affect protein and fat retention, whereas the ME to GE ratio decreased linearly with increased diet density. This suggests that diet density appears to affect digestibility rather than utilization of nutrients.
    High fat challenges and detection of early perturbations in endothelial health : the use of a comprehensive phenotyping approach
    Esser, D. - \ 2013
    Wageningen University. Promotor(en): Michael Muller, co-promotor(en): Lydia Afman. - S.l. : s.n. - ISBN 9789461735911 - 168
    endotheel - vetconsumptie - voedingsvet - lipidenmetabolisme - chocolade - endothelium - fat consumption - dietary fat - lipid metabolism - chocolate

    Background:Cardiovascular disease (CVD) is one of the leading causes of morbidity and mortality worldwide. One of the pathophysiology’s that play a pivotal role in the development and progression of CVD is a dysfunctional endothelium. An important lifestyle risk factor for endothelial dysfunction is the diet and several nutrients have been classified to be either beneficial or harmful for the endothelium. Although CVD usually affects middle-aged or older adults, the onset of endothelial dysfunction begins in early life, emphasising the need for primary prevention. We therefore aimed to identify markers of early perturbations in endothelial health by using dietary stressors, e.g. high fat (HF) challenge test. Thereafter we aimed to evaluate if the potential early markers are reversible and can be improved after an intervention with a dietary anti-stressor.

    Methods:First we validated the HF challenge test as a tool to trigger the endothelial response capacity. For that purpose, we compared the postprandial response after a HF shake with an average breakfast shake in young healthy men by assessing several plasma markers and functional measures of endothelial function. To identify new markers for early perturbations in endothelial health and to optimized the HF challenge test we applied three HF challenges differing in fatty acid type in two populations of middle-aged men, i.e. one at high- and one at low risk for developing CVD and characterized the postprandial response by applying high-throughput metabolomic and transcriptomic tools next to an extensive phenotyping of vascular function and vascular health parameters. Lastly, we evaluated if the, in the studies above, identified potential early biomarker profile is reversible and can be improved after an intervention with a dietary anti-stressor by means of a high flavanol chocolate intervention.

    Results:In young men, we observed that a HF challenge decreased flow mediated dilation (FMD), but this decrease was also found after the consumption of an average breakfast shake. IL-8 concentrations were more pronouncedly increased after HF shake consumption compared to an average breakfast control shake. In middle-aged men, a HF challenge decreased the augmentation index (AIX) and elicited an activated state of cellular adherence in the circulation as determined by increased plasma soluble adhesion molecules, increased leukocyte cell surface integrin and selectin expression and increased number of leukocytes. A challenge high in mono-unsaturated fatty acids (MUFAs) elicited the highest postprandial triglyceride (TG) concentrations and the most pronounced effects on AIX. By applying high-throughput metabolomic tools, we observed that oxylipin profiles were affected by the HF challenge and that these changes were depended on dietary fatty acid composition. Application of transcriptome profiling revealed that changes in peripheral blood mononuclear cell (PBMC) gene expression profiles after a HF challenge test were different between lean and obese subjects, with the most deviating effect after MUFA intake. The saturated fatty acid (SFA) shake decreased the expression of genes involved in cholesterol uptake and cholesterol biosynthesis and increased expression of genes involved in cholesterol efflux. MUFA increased expression of inflammatory genes and of peroxisome proliferator-activated receptor α (PPARα) target genes involved in β-oxidation. 4-week daily intake of a dietary anti-stressor, e.g. dark chocolate, increased fasting FMD and decreased AIX, and elicited a less activated state of cellular adherence, as determined by a decrease in plasma soluble adhesion molecules, a decrease in leukocyte cell surface integrin and selectin expression and a decrease in the number of leukocytes.

    Conclusions:In this thesis we extensively characterized the postprandial response to a HF challenge in human subjects with different disease risk profiles and optimized the HF challenge test. We identified MUFAs as most potent fatty acids to trigger the vascular and cellular response capacity, which makes it the optimal fatty acid type to use in a HF challenge test. We demonstrated that besides functional measures of vascular function, also plasma and cellular factors involved in leukocyte adhesion to the endothelium are adversely affected by dietary stressors and are beneficially affected by a dietary anti-stressor. Therefore, we conclude that endothelial health can be more comprehensively measured by means of a biomarker profile consisting not only of the vascular function measures FMD and AIX, but also of a subset of soluble adhesion molecules in the plasma, leukocyte counts and cell surface integrin and selectin expression. To identify potential new leads for biomarkers, we applied whole genome gene expression profiling, combined with the HF challenge test which enabled us to detect small differences in health status. Furthermore, we identified metabolic and inflammatory pathways that are specifically affected by either MUFAs or SFAs. These findings increased our understanding on how a SFA or MUFA challenge exert their distinct effects on stress related and metabolic compensatory cellular processes and provided us with new potential leads to detect early perturbations in endothelial health.

    Digestion of dietary fat : gastrointestinal behaviour of emulsions and human physiological responses
    Helbig, A. - \ 2013
    Wageningen University. Promotor(en): Harry Gruppen; Rob Hamer, co-promotor(en): Erika Silletti. - S.l. : s.n. - ISBN 9789461735607 - 166
    voedingsvet - spijsvertering - vetemulsies - spijsverteringskanaal - darmfysiologie - verzadigdheid - dietary fat - digestion - fat emulsions - digestive tract - intestinal physiology - satiety

    Two in vitromodels were used to understand emulsion behavior and the subsequent formation of free fatty acids (FFA), monoglycerides (MG) and diglycerides (DG). Emulsions stabilized by whey protein isolate (WPI) or gum arabic (GA), varying in droplet size, were digested under intestinal conditions. Concentrations of FFA, MG and DG, assessed by gas chromatography, decreased with increasing droplet size. FFA release from gum arabic-stabilized emulsions was higher compared to WPI-stabilized emulsions showing an influence of the interface. Next, lipolysis of protein stabilized emulsions (i.e. WPI or lysozyme) and the influence of flocculation at the isoelectric point (pI) were investigated in a dynamic gastrointestinal model. The stomach properties including gradual acidification caused WPI-stabilized emulsions to cream during transition through the pI of the protein. This resulted in delayed intestinal lipolysis compared to the lysozyme-stabilized emulsion. Thus, since gastric passage affects emulsion behavior and intestinal lipolysis, the gastric passage should be part of digestion models. Next, in a human study emulsion behavior and resulting lipolytic products were related to the release of satiety hormones, satiety perception and ad libitumintake. Also, gallbladder volume and oral processing were studied. A delayed entry into the duodenum and lipolysis for the un-homogenized sample resulted in lower CCK, delayed GLP-1/PYY responses and barely gallbladder contraction compared to the homogenized emulsion. No difference was found between treatments on ghrelin, only the perception 'desire to eat´ was elevated for homogenized emulsions. Oral processing induced prolonged gallbladder contraction, but had no additive effect on other measures. A homogenous system as such is possibly not effective to induce pronounced satiety perceptions compared to phase separated or creamed systems using the same emulsifier. Moreover, the release of gastrointestinal hormones cannot directly be related to the satiating effect of food.

    Dietary fat and the prevention of type 2 diabetes: impact on inflammation and underlying mechanisms
    Dijk, S.J. van - \ 2011
    Wageningen University. Promotor(en): Michael Muller, co-promotor(en): Edith Feskens; Lydia Afman. - [S.l.] : S.n. - ISBN 9789461730466 - 143
    diabetes type 2 - voedingsvet - ziektepreventie - genexpressieprofilering - biomarkers - ontsteking - nutrigenomica - type 2 diabetes - dietary fat - disease prevention - gene expression profiling - biomarkers - inflammation - nutrigenomics

    The incidence of metabolic syndrome, which is a risk factor for cardiovascular disease (CVD) and type 2 diabetes mellitus (T2DM) is increasing rapidly. Changes in dietary fat composition from saturated fat (SFA) to monounsaturated fat (MUFA) from olive oil, which is highly consumed in a Mediterranean diet, might improve risk factors for CVD and T2DM. However, the underlying molecular mechanisms for these beneficial health effects are not completely known. Moreover, more knowledge is needed about health status and biomarkers that allow early detection of onset of diseases such as metabolic syndrome, CVD and T2DM.

    The aim of this thesis was twofold; first, to investigate the acute and longer-term effects of intake of different types of dietary fat. Second, to examine whether a more comprehensive phenotyping of health status can be achieved by application of nutrigenomics tools and challenges tests.

    A controlled dietary intervention study was performed in healthy abdominally overweight subjects to investigate the effects of 8-weeks consumption of diets high in SFA or MUFA on insulin sensitivity, serum lipids and adipose tissue whole genome gene expression. Moreover, the effects of replacement of SFA by MUFA, as part of a western-type diet and as part of a Mediterranean diet, on peripheral blood mononuclear cell (PBMC) whole genome gene expression and plasma protein levels were investigated.

    Plasma protein profiles of the subjects before the intervention were used to define proteins and protein clusters that were associated with BMI and insulin concentrations. Similar analyses were performed in a second overweight population to verify the findings.

    In two other studies, the response capacity of subjects with different metabolic risk phenotypes to a high-fat challenge varying in fat type and to an extreme caloric restriction challenge were determined.

    Results from our first study showed that consumption of a SFA-rich diet increased expression of inflammation-related genes in adipose tissue whereas consumption of a MUFA-rich diet led to a more anti-inflammatory gene expression profile, without changes in insulin sensitivity or increases in body weight. Moreover, high MUFA intake from olive oil, both in a western-type diet and in a Mediterranean-type diet, lowered expression of genes involved in oxidative phosphorylation in PBMCs and lowered serum LDL and plasma ApoB, Connective Tissue Growth Factor and myoglobin concentrations.

    In plasma of the healthy participants clusters of proteinsassociated with BMI or insulin could be identified. These clusters included previously reported biomarkers for disease and potential new biomarkers.

    The high-fat challenge study showed that the plasma metabolic response and the PBMC gene expression response to high-fat challenges were affected by the presence of obesity and/or diabetes. Comparison of responses to high SFA, MUFA and n-3 PUFA loads showed that a highMUFA load induced the most pronounced response.

    The caloric restriction study revealed that PBMC gene expression profiles were different between metabolic syndrome subjects and healthy subjects, mainly for genes involved in pathways related to mitochondrial energy metabolism. Moreover, we observed that the caloric restriction challenge magnified differences in PBMC gene expression profiles between the subject groups.

    In conclusion, this thesis showed that 8-weeks consumption of a SFA-rich diet resulted in a pro-inflammatory gene expression profile in adipose tissue whereas consumption of a MUFA-rich diet caused a more anti-inflammatory profile, in addition to reductions in LDL cholesterol, some plasma proteins and expression of oxidative phosphorylation genes in PBMCs. Since the effects of the diets on inflammation were still local and not accompanied by systemic changes in inflammatory status or insulin sensitivity we hypothesize that adipose tissue could be an early response organ for dietary fat-induced changes. The changes in pro-inflammatory gene expression might be one of the first hallmarks in the development of adipose tissue inflammation and insulin resistance which on the longer term may lead to inflammation-related diseases such as metabolic syndrome.

    Our studies showed the potential of whole genome expression profiling, plasma profiling and the use of challenges tests to detect subtle diet effects and small differences in health status. Using these tools in future studies will result in more knowledge about health status and about mechanisms behind dietary effects. Eventually this might lead to earlier detection of small deviations from a healthy phenotype and to evidence-based dietary advice to improve health and to prevent disease.

    The fate of fat: tribology, adhesion and fat perception of food emulsions
    Dresselhuis, D.M. - \ 2008
    Wageningen University. Promotor(en): Martien Cohen Stuart, co-promotor(en): E.H.A. de Hoog; G.A. van Aken. - [S.l.] : S.n. - ISBN 9789085048657 - 152
    voedingsvet - vetten - emulsies - perceptie - tribologie - frictie - smering - adhesie - sensorische evaluatie - mond - orale biologie - dietary fat - fats - emulsions - perception - tribology - friction - lubrication - adhesion - sensory evaluation - mouth - oral biology
    Met de toename van het aantal mensen met overgewicht neemt ook de vraag naar producten die minder vet bevatten, maar nog steeds wel een lekker smaak hebben toe. Om zulke producten te maken is het heel belangrijk te weten wat er tijdens consumptie met het product gebeurt en hoe mensen eigenlijk vet waarnemen. We hebben ons in ons onderzoek vooral gericht op de bijdrage van vet op wat we noemen het mondgevoel en hoe fysische chemische processen in de mond dit kunnen beïnvloeden. Allereerst hebben we vastgesteld dat mensen als ze tijdens en na het consumeren van een vloeibaar product een lage frictie waarnemen tussen tong en verhemelte, ze dit associëren met vet en romigheid. In het tweede deel van het onderzoek hebben we aanwijzingen gevonden hoe de capaciteit van levensmiddelen-emulsies om een smerende laag op de tong te vormen (en dus de frictie in de mond te verlagen), afhangt van de kans dat de emulsiedruppels plakken (adhesie) en kunnen spreiden op de tong. Met deze kennis over plakken en spreiden van emulsies op de tong kunnen we nu emulsies proberen te maken waarbij we meer efficiënt gebruik maken van de hoeveelheid vet in het product en dus mogelijkheden scheppen om het vetgehalte te verlagen zonder aan smaak in te boeten.
    Maternal and child nutrition in rural Bangladesh: special reference to the effect of dietary fat supplementation on vitamin A status
    Alam, D.S. - \ 2001
    Wageningen University. Promotor(en): J.G.A.J. Hautvast; G.J. Fuchs; J.M.A. van Raaij. - S.l. : S.n. - ISBN 9789058084231 - 142
    maternale voeding - kindervoeding - voedingsvet - vitamine a tekort - zwangerschap - vrouwen - zogende vrouwen - plattelandsbevolking - bangladesh - maternal nutrition - child nutrition - dietary fat - vitamin a deficiency - pregnancy - women - lactating women - rural population - bangladesh

    The prevalence of maternal and child malnutrition in Bangladesh is one of the highest in the world. It is estimated that 50% of women of childbearing age suffer chronic energy deficiency (BMI<18.5), nearly half of infants are born with a low birth weight (<2.5 kg), and about 60% of preschool children are stunted. Protein energy malnutrition and deficiencies of micronutrient often coexist in pregnant and lactating women, in breastfed infants and in young children.

    This thesis reports the effect of daily supplementation with 18 g dietary fat from mid/late pregnancy until six months postpartum on the vitamin A status of mothers and their infants. The validity of a specific dietary assessment method to identify pregnant and lactating women at risk of vitamin A deficiency also has been examined and maternal energy intake during pregnancy and lactation was studied. Growth of infants in relation to breastfeeding practices, exclusive or non-exclusive, was assessed. Finally, the effect of diarrhoeal morbidity on growth of young children was examined. All studies were performed in rural Bangladesh.

    Results show that daily supplementation with 18 g of dietary fat has a beneficial effect on maternal vitamin A status during early lactation. Those supplemented with fat had relatively higher serumβ-carotene and lutein concentrations than those not supplemented. Measurement of vitamin A intake by the 24-hour vitamin A-focused recall was shown to be more reliable than the measurement by a food frequency questionnaire in identifying groups, groups not individual pregnant and lactating women at risk of vitamin A deficiency. Maternal energy intake during pregnancy and lactation was found to be low. The women gained insufficient weight during pregnancy and 48% delivered low birth weight infants. Women also lost 1 kg of body weight during the first six months of lactation. All infants were still breastfed at 6 mo, 70% and 37% were exclusively breastfed at 3 and 6 mo, respectively. There were no differences in morbidity and growth between the exclusive and non-exclusively breastfed infants however the growth of the exclusively breastfed infants more closely resembled that of WHO breastfed reference infants. In young children, dysentery (bloody diarrhoea) showed a significant negative association with ponderal and linear growth both in the 3 mo and 1 yr growth periods.

    From these findings it can be concluded that dietary fat supplementation may have a significant role in improving the vitamin A status of populations with a low fat intake and who derive their vitamin A mainly from provitamin A carotenoids. Poor maternal energy balance in otherwise poorly nourished women during pregnancy probably contributed to the extremely high prevalence of low birth weight in the community studied. What is lacking, however, is data on energy expenditure and that is required to precisely define the level of energy inadequacy. The similarity in growth pattern between our infants and that of WHO breastfed reference infants suggests that this growth pattern (i.e. the growth rate) might be physiologically optimal in this population, except that they start at a lower level due to low birth weight. This difference in growth, i.e. poorer weight, therefore is mainly attributable to the intrauterine rather than postnatal factors. It is also concluded that Infant and child nutrition can be substantially improved by preventing dysentery in this community.

    Body composition and diet of Chinese, Malays and Indians in Sininfluence on cardiovascular risk factorsgapore: and their
    Deurenberg-Yap, M. - \ 2000
    Agricultural University. Promotor(en): W.A. van Staveren; J.G.A.J. Hautvast. - S.l. : S.n. - ISBN 9789058082923 - 170
    lichaamssamenstelling - lichaamsvet - obesitas - voedselopname - calorieënopname - energieopname - voedingsvet - cholesterol - verzadigde vetten - onverzadigde vetten - vruchten - groenten - voedselgranen (hele korrel) - etnische groepen - cardiovasculair systeem - risicofactoren - singapore - body composition - body fat - obesity - food intake - caloric intake - energy intake - dietary fat - cholesterol - saturated fats - unsaturated fats - fruits - vegetables - whole grains - ethnic groups - cardiovascular system - risk factors - singapore

    This thesis describes the studies on body composition and dietary intakes of the three major ethnic groups residing in Singapore, and how these are related to cardiovascular risk factors in these groups.

    Body composition : Body fat percentage was measured using a four-compartment model described by Baumgartner. When the relationship between body mass index (BMI) and body fat percentage was studied, it was discovered that Singaporeans have higher percentage of body fat compared to Caucasians with the same BMI and that the BMI cut-off value for obesity in Chinese and Malays is around 27 kg/m 2 , while that for Indians is around 26 kg/m 2 . At levels of BMI and waist-to-hip ratio which are much lower than the WHO recommended cut-off limits for obesity and abdominal fatness respectively, both the absolute and relative risks of developing cardiovascular risk factors are markedly elevated for all three ethnic groups. Both the excessive fat accumulation and increased risks at low levels of BMI signal a need to re-examine cut-off values for obesity among Chinese, Malays and Indians.

    Diet : Dietary intakes of energy, total fat, saturated fat, polyunsaturated fat, monounsaturated fat and cholesterol were measured using a food frequency questionnaire specially validated for this purpose. In addition, intakes of fruits, vegetables and grain-based foods were also measured using the same questionnaire. Singaporeans generally have a low intake of fruits, vegetables and whole grain products. The intake of total fat is just within the upper recommended limit while that for saturated fat is higher than the recommended level. On a group level, it is found that high intakes of fat, saturated fat and low intakes of polyunsaturated fat and vegetables affect serum cholesterol levels adversely. However, on an individual level, due to the rather homogenous intake patterns among the three groups, this cross sectional study was unable to demonstrate that dietary intakes could explain the differences in serum cholesterol levels among ethnic groups.

    In summary, the thesis shows that in the light of increased body fat percentage and cardiovascular risks at low BMI, there is a need to re-examine the WHO's cut-off values for the three major ethnic groups in Singapore. Longitudinal studies are also needed for better insight into the effect of dietary intakes and other lifestyle risk factors on cardiovascular risk factors and mortality.

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