The aim of the present study was to determine the relationship of BMI with other cardiovascular risk factors, leisure-time physical activity and diet. Participants were recruited in a cross-sectional population-based survey in a southern-Europe Mediterranean population (Spain); cardiovascular risk factors were measured, and leisure-time physical activity and diet intake were evaluated. Linear regression analysis adjusted for several confounders showed a significant, direct association of BMI and total cholesterol (P<0·005) and LDL-cholesterol (P<0·006), in men. HDL-cholesterol was inversely related to BMI in both sexes (P<0·0001). Higher BMI was more frequent in less-active men (P<0·04) but not in women. BMI increased significantly (P<0·0001) by 1·92 kg/m2 with each 4·18 MJ consumed in men but not in women. Dietary intakes of carbohydrate (P<0·03), total fat (P<0·03) and saturated fatty acids (P<0·02) were directly associated with BMI in men but not in women, in whom protein intake was correlated (P<0·001) with BMI. Linear regression models including dietary components explained up to 10·6 and 21·1 % of BMI variability in men and women, respectively. Sex differences in the association of BMI with total cholesterol, and LDL-cholesterol, may account for the lower risk for CHD in women compared with men of similar BMI reported in the literature for the southern-Europe Mediterranean region. An increases of BMI may be more deleterious in populations in which it is accompanied by other risk factors such as a higher intake of total fat and, particularly, of saturated fatty acids, or lower leisure-time physical activity.

The aim of the present study was to assess the nutritional status for thiamin (vitamin B1) and riboflavin (vitamin B2) in an adult Mediterranean population, in order to identify patterns of intake, groups at risk for deficiency and factors that might influence this risk. A cross-sectional survey was carried out in Andalusia, a western Mediterranean region in southern Spain. Nutrient intakes were studied in a random sample of 3390 subjects (1746 men, 1644 women) who were between 25 and 60 years of age. Blood samples were obtained for biochemical assays in a random subsample of 372 subjects (181 men, 191 women). Food consumption was assessed by 48 h recall. Vitamin B1 and B2 were measured as erythrocyte transketolase and as erythrocyte glutathione reductase activation coefficients, respectively. Energy and vitamin intakes were significantly higher in men than in women. Intakes were below two-thirds of the recommended dietary allowance for vitamin B1 in 7·80% of the men and 4·50% of the woman, and were below this level for vitamin B2 in 18·00% of the men and 11·70 % of the women. Age, educational level, alcohol use and smoking were also associated with differences in the intake of these nutrients. Biochemical analyses showed that vitamin B1 and B2 status was deficient in 6·40 and 5·30% of the population, respectively. Although factors such as gender, age, level of education, drinking and smoking can have an effect on the risk of inadequate intake of these nutrients, these factors did not affect biochemical indices of nutritional status in the present study.

The bacterial single-cell protein BioProtein (BP; Norferm Danmark, Odense, Denmark), produced by fermentation of natural gas with methanotrophic bacteria, is a potential protein source for man and animals. For human consumption, removal of the nucleic acid is necessary. Preliminary studies have shown that ingested BP induces a specific immune response. The objective of the present study was to characterize the type of response, its development over time and product-related causative factors. Mice were fed with diets containing 60 g nucleic acid-reduced BP/kg, 240 g nucleic acid-reduced BP/kg, 240 g untreated BP (basic BP)/kg or 240 g casein/kg (control). In another study, mice were fed 240 g basic BP/kg, whole cell-free BP-culture homogenate or control diet. The immune response was monitored using an ELISA for BP-specific immunoglobulin in blood and BP-specific immunoglobulin A in blood and saliva. Ingested BP induced a steady specific mucosal and systemic immune response, characterized by a dose-dependent production of immunoglobulin and immunoglobulin A in blood and immunoglobulin A in saliva. Basic BP and nucleic acid-reduced BP induced identical responses. However, feeding mice BP-culture homogenate induced immunoglobulin A in saliva but there was no systemic response. The antibodies from BP-fed mice cross-reacted with BP-culture homogenate revealing the presence of the same antigenic components in the two products despite the different oral immunogenicity. Thus, ingestion of BP induces a persistent mucosal and systemic immune response of which the systemic response can be avoided by ingesting a BP preparation free of whole cells. This indicates the importance of the non-particulate constitution of single-cell protein products intended for human or animal consumption.

The aim of the present analysis was to evaluate the effect of intake of added sugars on intakes of nutrients and food groups. We used a mixed linear model (PROC MIXED) to analyse data from the Dortmund Nutritional and Anthropometric Longitudinally Designed (DONALD) study (an ongoing longitudinal cohort study between infancy and adulthood). Between July 1985 and August 2001, 3 d weighed dietary records (n 4993) from 849 children and adolescents (416 male, 433 female) aged 2–18 years were collected and evaluated. Overall mean intake of added sugars was 12·4 (SD 5·3) (median 12·0) % energy. Fat intake (% energy) and intake of all analysed nutrients (as % reference values for nutrient intakes) fell across quintiles 1–5 of energy intake from added sugars (P<0·001). With the exception of ‘Sugary foods’ and ‘Beverages’ (significant increase, P<0·0001) and ‘Dairy’ (NS), intake of all other food groups decreased with increasing intake of added sugars (P<0·0001). In conclusion, we found a slight, but statistically significant, nutrient-dilution effect of added sugars and a significant reduction in intake of important nutrient-bearing food groups. However, the DONALD study gives no clear indicator on grounds of micronutrient dilution for a quantitative limit on intake of added sugars.

Several studies have used factor analysis to identify food intake patterns in epidemiological studies as an alternative to nutrient-based analyses, but few have validated the factors in a larger population. Our present objectives were: to compare the factor scores based on a food-frequency questionnaire (FFQ) with scores based on a 7 d diet record; to examine the consistency of the factor score correlations across strata of age, BMI, energy intake, education, physical activity and smoking and to compare factors identified in two sub-populations. In 879 men and 927 women, of the total population sample of 3785, scores on food intake factors, three for men (‘green’, sweet’ and ‘traditional’) and two for women (‘green’ and ‘sweet–traditional’), identified in data from the FFQ and the diet record, were compared. The loadings of foods on the factors were very similar and the correlations between the corresponding factor scores, based on the two dietary assessment methods, were: for men ‘green’ 0·61, ‘sweet’ 0·55, ‘traditional’ 0·34; for women, ‘green’ 0·61, ‘sweet–traditional’ 0·57. Stratification did not significantly modify the correlations, with a few inconsistent exceptions. Factors obtained in a different subsample of the population, for which there was only data from the FFQ, were almost identical to the factors found in the subsample, who provided both FFQ and diet record information with regard to food loadings and model fit. In conclusion, the food intake factors identified were reproducible using two different dietary assessment methods and, furthermore, independent of stratification.

Cluster of differentiation molecule (CD)3 and CD28 receptors play crucial roles in T-lymphocyte proliferation. Fe deficiency in man and animals impairs T-lymphocyte proliferation by unknown mechanisms. To test the hypothesis that reduced CD3 and CD28 expression is one of them, thymocytes and splenocytes from control (C; n 24), Fe-deficient (ID; n 24), pair-fed (PF; n 24), and ID mice that were Fe-repleted for 3 (R3; n 24) or 14d (R14; n 12) were labelled with anti-CD3-fluorescein isothiocyanate and anti-CD28-phycoerythrin antibodies. Positive cells were analysed by flow cytometry. Significant differences were observed among groups in the mean levels of haemoglobin and liver Fe stores (C=PF=R14>R3>ID; P<0·005). While Fe deficiency slightly increased the percentage of CD3+ splenocytes, it reduced that of CD28+ thymocytes in mice with thymus atrophy and splenomegaly (P<0·05). These changes were corrected by Fe repletion. CD28 mean fluorescence intensity (FI) was lower and CD3 FI was higher in lymphocytes from R3 and ID, especially those with splenomegaly, than in those from R14 and PF mice (P<0·05). In vitro Fe chelation by deferoxamine (60min) significantly decreased CD28 expression (P<0·05), and slightly increased that of CD3 (P>0·05). Spleen cell proliferative responses to concanavalin A and anti-CD3±anti-CD28 were reduced by Fe deficiency (ID≤R3<C=PF<R14; P<0·05); and they correlated with FI and percentages of CD3+ and CD28+ cells (r≤0·69; P<0·05). Indicators of Fe status negatively correlated with CD3 FI (r−0·23), but positively correlated with CD28 FI (r≤0·44; P<0·05). Data suggest that altered CD28 expression may contribute to reduced T-cell proliferation during Fe deficiency.

Recent studies have revealed that retinoids play an important role in the adult central nervous system and cognitive functions. Previous investigations in mice have shown that vitamin A deficiency (VAD) generates a hypo-expression of retinoic acid (RA, the active metabolite of vitamin A) receptors and of neurogranin (RC3, a neuronal protein involved in synaptic plasticity) and a concomitant selective behavioural impairment. Knowing that RC3 is both a triiodothyronine (T3) and a RA target gene, and in consideration of the relationships between the signalling pathways of retinoids and thyroid hormones, the involvement of T3 on RA signalling functionality in VAD was investigated. Thus, the effects of vitamin A depletion and subsequent administration with RA and/or T3 on the expression of RA nuclear receptors (RAR, RXR), T3 nuclear receptor (TR) and on RC3 in the brain were examined. Rats fed a vitamin A-deficient diet for 10 weeks exhibited a decreased expression of RAR, RXR and TR mRNA and of RC3 mRNA and proteins. RA administration to these vitamin A-deficient rats reversed only the RA hypo-signalling in the brain. Interestingly, T3 is able to restore its own brain signalling simultaneously with that of vitamin A and the hypo-expression of RC3. These results obtained in vivo revealed that one of the consequences of VAD is a dysfunction in the thyroid signalling pathway in the brain. This seems of crucial importance since the down regulation of RC3 observed in the depleted rats was corrected only by T3.

The increasing interest in a healthy diet is stimulating innovative development of novel scientific products in the food industry. The viable lactic acid bacteria in fermented milk products, such as yoghurt, have been associated with increased lactose tolerance, a well-balanced intestinal microflora, antimicrobial activity, stimulation of the immune system and antitumoural, anticholesterolaemic and antioxidative properties in human subjects. Recently, we have studied a human Lactobacillus spp. strain that possesses antioxidative activity. The aim of the present pilot study was to develop goats' milk fermented with the human antioxidative lactobacilli strain, Lactobacillus fermentum ME-3, and to test the effect of the fermented probiotic goats' milk on oxidative stress markers (including markers for atherosclerosis) in human blood and urine and on the gut microflora. Twenty-one healthy subjects were assigned to two treatment groups: goats' milk group and fermented goats' milk group (150 g/d) for a period of 21 d. Consumption of fermented goats' milk improved anti-atherogenicity in healthy subjects: it prolonged resistance of the lipoprotein fraction to oxidation, lowered levels of peroxidized lipoproteins, oxidized LDL, 8-isoprostanes and glutathione redox ratio, and enhanced total antioxidative activity. The consumption of fermented goats' milk also altered both the prevalence and proportion of lactic acid bacteria species in the gut microflora of the subjects. We conclude that the goats' milk fermented with our special antioxidative lactobacilli strain Lactobacillus fermentum ME-3 exhibits anti-atherogenic effects.

The present study was conducted to determine the iodine concentration in Norwegian-produced milk and a selection of dairy products. The iodine concentration of eighty-five samples of milk and dairy products was analysed by inductively coupled plasma–MS. Low-fat milk and organic milk were sampled from nineteen and seven different locations in Norway, respectively, during the summer and winter season of 2000. Other milk and dairy products were chiefly collected during the summer season. Low-fat milk from the summer season had significantly lower median iodine concentration (88 μg/l, range 63–122 μg/l) compared with low-fat milk from the winter season (232 μg/l, range 103–272 μg/l). The median iodine concentration of organic summer milk (60 μg/l) was significantly lower than the iodine concentration of organic winter milk (127 μg/l). There were no significant differences in the low-fat-milk samples with regard to geographical sampling location. Whey cheese (Tine Gudbrandsdalsost) iodine concentration was significantly higher (803 μg/kg) than the median iodine concentration in casein cheeses such as Jarlsberg and Norvegia of 201 and 414 μg/kg, respectively. With a recommended iodine intake of 150 μg/d for adults, a daily intake of 0.4 litres milk meets the requirement with 25% during the summer and more than 60% during the winter season. Thus, milk and dairy products are important determinants of iodine intake in Norway.

Evidence indicates that cruciferous vegetables are protective against a range of cancers with glucosinolates and their breakdown products considered the biologically active constituents. To date, epidemiological studies have not investigated the intakes of these constituents due to a lack of food composition databases. The aim of the present study was to develop a database for the glucosinolate content of cruciferous vegetables that can be used to quantify dietary exposure for use in epidemiological studies of diet–disease relationships. Published food composition data sources for the glucosinolate content of cruciferous vegetables were identified and assessed for data quality using established criteria. Adequate data for the total glucosinolate content were available from eighteen published studies providing 140 estimates for forty-two items. The highest glucosinolate values were for cress (389 mg/100 g) while the lowest values were for Pe-tsai chinese cabbage (20 mg/100 g). There is considerable variation in the values reported for the same vegetable by different studies, with a median difference between the minimum and maximum values of 5·8-fold. Limited analysis of cooked cruciferous vegetables has been conducted; however, the available data show that average losses during cooking are approximately 36 %. This is the first attempt to collate the available literature on the glucosinolate content of cruciferous vegetables. These data will allow quantification of intakes of the glucosinolates, which can be used in epidemiological studies to investigate the role of cruciferous vegetables in cancer aetiology and prevention.

In a randomised, single blind, placebo-controlled crossover design study, we investigated whether healthy, non-smoking, dietary unrestrained women (n 24), divided into linoleic acid tasters (LAT, n 14) and linoleic acid non-tasters (LANT, n 10), differed in food intake regulation when linoleic acid was added to ice creams. The determination of subjects as LAT or LANT was done using a 10μM-linoleic acid solution. The ice creams were characterised by the subjects and a taste perception test using the triangle test was conducted three times. Food intake and appetite were measured using the universal eating monitor. LAT and LANT did not differ in characterisation or in taste perception of the ice creams, even though LAT were able to increase their ability to discriminate between the ice cream with linoleic acid from the one containing oleic acid. No effect of LAT status or type of ice cream was found for hedonic value of the ice creams. Linoleic acid taster status did affect food intake regulation. For LAT, but not LANT, the amount eaten was a function of Δsatiety. Subjects ate by weight of food and not by energy content. In conclusion, differences in food intake regulation were seen between LAT and LANT, in that the amount eaten by LAT was a function of Δsatiety, but was not for LANT.

Epidemiological studies indicate that Asian women have a lower breast cancer incidence compared with their counterparts in the West, and the difference has been related to soya consumption. Animal studies have suggested that soya may prevent dimethylbenz[a]anthracene (DMBA)-induced carcinogenesis in the breast. In the present study a cell culture model was developed to address the effect of soya isoflavones on the DMBA-induced DNA damage. DMBA is metabolized into a DNA-attacking moiety by two phase I cytochrome P450 (CYP) enzymes CYP1A1 and CYP1B1. DNA mutation caused by this genotoxic agent is a crucial step in cancer initiation. Substances that interfere with the CYP1 enzyme activities can affect the initiation. In the present study, genistein was found to be an effective inhibitor of recombinant human CYP1A1 and CYP1B1 with Ki of 15·35 and 0·68 μmol/l. The other soya isoflavone daidzein, on the other hand, did not demonstrate any significant inhibition of the enzyme activities. At the transcriptional level, DMBA induced the CYP1 enzyme expressions by stimulating the xenobiotic response element (XRE)-dependent transactivation pathway. When genistein (25 μmol/l) was co-administered with DMBA, the XRE-Luc activity the CYP1 mRNA abundances were significantly suppressed. The present study illustrated that the soya isoflavone genistein, but not daidzein, protected against DMBA genotoxicity.

Enterostatin (ENT) has been found to inhibit food intake and selectively inhibit fat intake in rats. Both peripheral and central mechanisms have been proposed. It also has been suggested that ENT may increase thermogenesis. The present study investigated the effects of oral ENT administration on food intake, energy expenditure and body weight in subjects with a preference for a high-fat diet. In a double-blind, placebo-controlled, randomized and crossover design, nine female and three male healthy subjects (age 34 (sd 11) years, BMI 24·5 (sd 2·5) kg/m2) with a preference for a high-fat diet ingested ENT (3 × 15 mg/d) or placebo (PLA) while consuming a high-fat diet ad libitum for 4d. Eight subjects ended each intervention with a 36h stay in the respiration chamber, continuing the diet and treatment. Body-weight loss was significant (ENT 0·8 (se 0·3) kg, P<0·05; PLA 1·3 (se 0·3) kg, P<0·001), but not different between treatments. There was no difference between treatments in total energy intake (ENT 37·1 (se 2·6), PLA 35·9 (se 3·2) MJ), macronutrient composition, hunger, satiety and hedonic scores during the 4d high-fat diet. Energy expenditure (24h) (ENT 9·6 (se 0·4), PLA 9·5 (se 0·4) MJ), sleeping and resting metabolic rate, diet-induced thermogenesis, activity-induced energy expenditure and 24h RQ (ENT 0·77 (se 0·01), PLA 0·77 (se 0·01)) were similar for both treatments. We conclude that oral ENT administration did not affect food intake, energy expenditure or body weight in subjects with a preference for a high-fat diet experiencing a negative energy and fat balance.

Epidemic spastic paraparesis (konzo) found in tropical and subtropical countries is known to be caused by long-term intake of cassava (Manihot esculenta Crantz), which contains a cyanoglucoside linamarin (α-hydroxyisobutyronitrile-β-D-glucopyranoside). It has been reported that linamarin is enzymatically converted to cyanide by bacteria in the intestine, and this is absorbed into the blood and then damages neural cells. However, unmetabolized linamarin was found in the urine after oral administration of cassava; thus, we hypothesized that konzo could be caused by direct toxicity of the unmetabolized linamarin that was transferred to the brain and could be transported into neural cells via a glucose transporter. In the present study it was confirmed that linamarin directly damaged neural culture pheochromocytoma cell (PC) 12 cells; 0·10 mM-linamarin caused cell death at 13·31 (SD 2·07) %, which was significantly different from that of control group (3·18 (SD 0·92) %, P=0·0004). Additional 10 μM-cytochalasin B, an inhibitor of a glucose transporter, prevented cell death: the percentage of dead cells significantly decreased to 6·06 (SD 1·98), P=0·0088). Furthermore, glucose also prevented cell death. These present results strongly suggest that linamarin competes with cytochalasin B and glucose for binding to a glucose transporter and enters into cells via glucose transporter.

The aim of the present study was to evaluate air-displacement plethysmography (ADP) in children aged 5–7 years. Body-composition measurements were obtained by ADP, 2H dilution and anthropometry in twenty-eight children. Calculation of body volume by ADP was undertaken using adult and children's equations for predicting lung volume and surface area. Fat-free mass (FFM) was calculated using a three-component model. Measured FFM hydration was then compared with values from the reference child. Differences between measured and reference hydration were back-extrapolated, to calculate the error in ADP that would account for any disagreement. Propagation of error was used to distinguish the contributions of methodological precision and biological variability to total hydration variability. The use of children's equations influenced the results for lung volume but not surface area. The mean difference between measured and reference hydration was 0·6 (sd 1·7) % (P < 0·10), equivalent to an error in body volume of 0·04 (sd 0·20) litres (P < 0·30), and in percentage fat of 0·4 (sd 1·9) (P < 0·28). The limits of agreement in individuals could be attributed to methodological precision and biological variability in hydration. It is concluded that accuracy of ADP was high for the whole group, with a mean bias of < 0·5 % fat using the three-component model, and after taking into account biological variability in hydration, the limits of agreement were around ±2% fat in individuals. Paediatric rather than adult equations for lung volume estimation should be used.

There are few validated methods of measuring dietary fatty acid intake that are suitable for epidemiological research. The purpose of the present study was to develop and validate a food-frequency questionnaire (FFQ) developed to measure individual dietary fatty acid intakes against 7d weighed dietary records, in a sample of thirty-one healthy adult volunteers. The FFQ was based on a previously validated questionnaire (DIETQ; Tinuviel Software, Warrington, Ches., UK), adapted to include greater detail on those foods from which the majority of dietary fatty acids are obtained. The FFQ and weighed records were analysed using food nutrient data from McCance and Widdowson's Food Composition Tables, supplemented with a food fatty acid content database (Foodbase, London, UK). Results from the two dietary assessment methods were compared by correlation coefficients and limits of agreement. The mean intake of individual fatty acids tended to be lower when assessed by FFQ. Correlation coefficients comparing unadjusted individual fatty acid intakes assessed by FFQ and weighed records ranged from 0·29 for 18:1n−9 to 0·71 for 20:4n−6. Adjusting for energy intake tended to increase the correlation coefficients between saturated fatty acids and decrease those between unsaturated fatty acids. In conclusion, this food-frequency method provides reliable estimates of dietary intake of many individual fatty acids for use in epidemiological studies.

Enhancing the polyunsaturated fatty acid (PUFA) and decreasing the saturated fatty acid content of beef is an important target in terms of improving the nutritional value of this food for the consumer. The present study examined the effects of feeding a ruminally protected lipid supplement (PLS) rich in PUFA on the fatty acid composition of longissimus thoracis muscle and associated subcutaneous adipose tissue. Animals were fed ad libitum on grass silage plus one of three concentrate treatments in which the lipid source was either Megalac (rich in palmitic acid; 16:0) or PLS (soyabean, linseed and sunflower-seed oils resulting in an 18:2n−6:18:3n−3 value of 2·4:1). Treatment 1 contained 100g Megalac/kg (Mega, control); treatment 2 (PLS1) contained 54g Megalac/kg with 500g PLS/d fed separately; treatment 3 (PLS2) contained no Megalac and 1000g PLS/d fed separately. The PLS was considered as part of the overall concentrate allocation per d in maintaining an overall forage:concentrate value of 60:40 on a DM basis. Total dietary fat was formulated to be 0·07 of DM of which 0·04 was the test oil. Total intramuscular fatty acids (mg/100g muscle) were decreased by 0·31 when feeding PLS2 compared with Mega (P<0·05). In neutral lipid, the PLS increased the proportion of 18:2n−6 and 18:3n−3 by 2·7 and 4·1 on diets PLS1 and PLS2 v. Mega, respectively. Similar responses were noted for these fatty acids in phospholipid. The amounts or proportions of 20:4n−6, 20:5n−3 or 22:6n−3 were not influenced by diet whereas the amounts and proportions of 22:4n−6 and 22:5n−3 in phospholipid were decreased with inclusion of the PLS. The amounts of the saturated fatty acids, 14:0, 16:0 and 18:0, in neutral lipid were on average 0·37 lower on treatment PLS2 compared with Mega. Feeding the PLS also decreased the proportion of 16:0 in neutral lipid. The amount of 18:1n-9 (P=0·1) and the amount and proportion of 18:1 trans (P<0·01) were lower on treatments PLS1 and PLS2 in neutral lipid and phospholipid. Conjugated linoleic acid (cis-9, trans-11) was not influenced by diet in the major storage fraction for this fatty acid, neutral lipid. The PUFA:saturated fatty acids value was increased markedly (×2·5) with inclusion of the PLS (P<0·001) while the σn−6:n−3 value increased slightly (×1·2; P=0·015). The results suggest that the protected lipid used, which was rich in PUFA, had a high degree of protection from the hydrogenating action of rumen micro-organisms. The PLS resulted in meat with a lower content of total fat, decreased saturated fatty acids and much higher 18:2n−6 and 18:3n−3. The net result was a large shift in polyunsaturated: saturated fatty acids, 0·28 v. 0·08, on feeding PLS2 compared with Mega, respectively.

The UK Food Standards Agency convened a group of expert scientists to review current research investigating folate bioavailability. The workshop aimed to overview current research and establish priorities for future research. Discrepancies were observed in the evidence base for folate bioavailability, especially with regard to the relative bioavailability of natural folates compared with folic acid. A substantial body of evidence shows folic acid to have superior bioavailability relative to food folates; however, the exact relative bioavailability still needs to be determined, and in particular with regard to mixed diets. The bioavailability of folate in a mixed diet is probably not a weighted average of that in the various foods consumed; thus the workshop considered that assessment of folate bioavailability of whole diets should be a high priority for future research.

A randomised crossover study of eight overweight or obese men (aged 24–49 years, BMI 25.5–31.3 kg/m2), who followed two diets for 4 weeks each, was performed to determine whether substitution of saturated fat with monounsaturated fat affects body weight and composition. Subjects were provided with all food and beverages as modules (selected ad libitum) of constant macronutrient composition, but differing energy content. The % total energy from saturated fat, monounsaturated fat and polyunsaturated fat was 24, 13 and 3% respectively on the saturated fatty acid (SFA)-rich diet and 11, 22 and 7% respectively on the monounsaturated fatty acid (MUFA)-rich diet. MUFA accounted for about 80% of the unsaturated fats consumed on both diets. Body composition, blood pressure, energy expenditure (resting and postprandial metabolic rates, substrate oxidation rate, physical activity), serum lipids, the fatty acid profile of serum cholesteryl esters and plasma glucose and insulin concentrations were measured before and after each diet period. Significant (P≤0·05) differences in total cholesterol and the fatty acid composition of serum cholesteryl esters provided evidence of dietary adherence. The men had a lower weight (-2·1 (se 0·4) kg, P=0·0015) and fat mass (-2·6 (se 0·6) kg, P= 0·0034) at the end of the MUFA-rich diet as compared with values at the end of the SFA-rich diet. No significant differences were detected in energy or fat intake, energy expenditure, substrate oxidation rates or self-reported physical activity. Substituting dietary saturated with unsaturated fat, predominantly MUFA, can induce a small but significant loss of body weight and fat mass without a significant change in total energy or fat intake.

It is well established that in human subjects a proportion of urea production undergoes hydrolysis in the gastrointestinal tract with release of N potentially available for amino acid synthesis. Previous studies have suggested adaptive changes in urea kinetics, with more urea-N retained within the metabolic pool during reduced dietary intakes of energy and protein. We therefore investigated the effect of rate and extent of weight loss on adaptive changes in urea kinetics in two groups (each n 6) of obese men (mean age 43 (sd 12) years, BMI 34·8 (sd 2·9)kg/m2) during either total starvation for 6d or a very-low-energy diet (2·55MJ/d) for 21d. Subjects were resident in the Human Nutrition Unit of the Rowett Research Institute (Aberdeen, Scotland, UK) and lost 6 and 9% initial body weight within the starvation and dieting groups respectively. Changes in urea-N metabolism were assessed by stable isotope tracer kinetics using [15N15N]urea infused intravenously for 36h before, during and after weight loss. In response to weight loss, urea production decreased (P<0·01) by 25% from 278 to 206μmol urea-N/h per kg within the dieting group only. However, no changes were observed in the proportion of urea being hydrolysed in the gastrointestinal tract (range 20–25%) or in the proportion of N retained for anabolic purposes (80–85% urea-N from gastrointestinal hydrolysis) within either group. It was concluded that no adaptive changes in urea kinetics occurred in response to either the different rate or extent of weight loss.