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PubMed1994

Indirect measurement of saliva secretion in sheep fed diets of different structures and the effect of such diets on ruminal fluid kinetics and fermentation pattern.

Four Suffolk x Dorset sheep were allocated in a 4 x 4 Latin square design and received a hay-barley-molasses diet in one of four different physical structures: (1) pelleted; (2) pelleted:chopped (60:40); (3) chopped:pelleted (60:40); or (4) chopped. The animals were penned individually and the diet was restricted to provide 20 g of dry matter (DM) per kilogram live weight daily. The effects of the diets on rumen fluid kinetics, fermentation pattern and microbial nitrogen (MN) supply were examined. Saliva secretion was estimated using an indirect method based on water balance in the rumen. When the animals were fed the chopped diet, the salivation rate, rumen fluid volume and rumen liquid outflow were all increased significantly (P < 0.05 to P < 0.01). No consistent effect of dietary structure on rumen fluid dilution rate, purine derivative (PD) excretion or MN supply was observed. Dietary structure had no effect on the rumen fermentation pattern, digestibility of DM or nitrogen.

Animal Feed↗

PubMed1996

Effects of diet and diet-plus-exercise programs on resting metabolic rate: a meta-analysis.

Studies examining the effects of diet (D) and diet-plus-exercise (DE) programs on resting metabolic rate (RMR) report equivocal results. The purpose of this study was to use meta-analysis to determine if exercise prevents the decrease in RMR observed with dieting. Results from the 22 studies included in this analysis revealed that the majority of studies used female subjects ages 31-45 years, who were fed a relatively low-fat, high-carbohydrate diet of less than 5,023 kJ.day-1. The predominant prescribed exercise was aerobic in nature, 31-60 min in duration, performed 4-5 days per week, and of moderate intensity (51-70% of VO2max). Contrary to what is reported in narrative reviews, RMR decreased significantly with both D and DE programs, and the drop with D was significantly greater than that with DE. In conclusion, the addition of exercise to dietary restriction appears to prevent some of the decrease in RMR observed in premenopausal women.

Adult↗

PubMed2006

A whey-supplemented, high-protein diet versus a high-carbohydrate diet: effects on endurance cycling performance.

This study compared a training diet recommended for endurance athletes (H-CHO) with an isoenergetic high protein (whey supplemented), moderate carbohydrate (H-Pro) diet on endurance cycling performance. Over two separate 7-d periods subjects (n = 7) ingested either H-CHO (7.9 +/- 1.9 g x kg(-1) x d(-1) carbohydrate; 1.2 +/- 0.3 g x kg(-1) x d(-1) fat; 1.3 +/- 0.4 g x kg(-1) x d(-1) protein) or H-Pro (4.9 +/- 1.8 g x kg(-1) x d(-1); 1.3 +/- 0.3 g x kg(-1) x d(-1); 3.3 +/- 0.4 g x kg(-1) x d(-1)) diet in a randomized, balanced order. On day 8 subjects cycled (self-paced) for a body weight dependent (60 kJ/bm) amount of work. No differences occurred between energy intake (P = 0.422) or fat intake (P = 0.390) during the two dietary conditions. Performance was significantly (P = 0.010) impaired following H-Pro (153 +/- 36) compared with H-CHO (127 +/- 34 min). No differences between treatments were observed for physiological measures taken during the performance trials. These results indicate an ergolytic effect of a 7-d high protein diet on self-paced endurance cycling performance.

Adult↗

PubMed1987

Evidence for liver as the major site of the diet-induced thermogenesis of rats fed a "cafeteria" diet.

The resting metabolic rates (VO2) of rats fed chow (CH) or a "cafeteria" (CAF) diet of highly palatable human foods were measured at thermoneutrality (28 degrees C) before and shortly after two-thirds hepatectomy or sham operation, and again after administration of propranolol (5 mg/kg). CAF rats initially had a 17% and 1.2 mL/min higher mean resting VO2 than CH rats, a difference usually considered to represent the diet-induced thermogenesis (DIT) that CAF rats develop during overconsumption of the diet. Sham operation did not significantly affect resting VO2 in either diet group. Two-thirds hepatectomy decreased VO2 by about 1.0 mL/min more (125% more) in CAF rats than in CH rats, from which it may be estimated that the CAF rats initially had a liver VO2 about 1.6 mL/min higher than that of the CH rats, a difference more than sufficient to fully account for their apparent DIT. Propranolol did not significantly affect the VO2 of CH rats. It reduced the VO2 of sham-operated CAF rats by 0.94 +/- 0.08 mL/min (12%), but had a significantly smaller effect (delta VO2 = -0.50 +/- 0.05 mL/min) in partially hepatectomized CAF rats. This difference suggests that about 70% of the propranolol-inhibitable fraction of the elevated VO2 of the CAF rats, presumably a measure of sympathetically mediated DIT, resided in the liver. This study thus points to the liver as the major (70-100%) effector of the DIT of CAF rats.

Animals↗

PubMed2006

Comparative effects of a low-carbohydrate diet and exercise plus a low-carbohydrate diet on muscle sarcoplasmic reticulum responses in males.

We employed a glycogen-depleting session of exercise followed by a low-carbohydrate (CHO) diet to investigate modifications that occur in muscle sarcoplasmic reticulum (SR) Ca(2+)-cycling properties compared with low-CHO diet alone. SR properties were assessed in nine untrained males [peak aerobic power (Vo(2 peak)) = 43.6 +/- 2.6 (SE) ml.kg(-1).min(-1)] during prolonged cycle exercise to fatigue performed at approximately 58% Vo(2 peak) after 4 days of low-CHO diet (Lo CHO) and after glycogen-depleting exercise plus 4 days of low-CHO (Ex+Lo CHO). Compared with Lo CHO, Ex+Lo CHO resulted in 12% lower (P < 0.05) resting maximal Ca(2+)-ATPase activity (V(max) = 174 +/- 12 vs. 153 +/- 10 micromol.g protein(-1).min(-1)) and smaller reduction in V(max) induced during exercise. A similar effect was observed for Ca(2+) uptake. The Hill coefficient, defined as slope of the relationship between cytosolic free Ca(2+) concentration and Ca(2+)-ATPase activity, was higher (P < 0.05) at rest (2.07 +/- 0.15 vs. 1.90 +/- 0.10) with Ex+Lo CHO, an effect that persisted throughout the exercise. The coupling ratio, defined as the ratio of Ca(2+) uptake to V(max), was 23-30% elevated (P < 0.05) at rest and during the first 60 min of exercise with Ex+Lo CHO. The approximately 27 and 34% reductions (P < 0.05) in phase 1 and phase 2 Ca(2+) release, respectively, observed during exercise with Lo CHO were not altered by Ex+Lo CHO. These results indicate that when prolonged exercise precedes a short-term Lo CHO diet, Ca(2+) sequestration properties and efficiency are improved compared with those during Lo CHO alone.

Adult↗

PubMed2006

Differential effects of endothelin on activation of renal mechanosensory nerves: stimulatory in high-sodium diet and inhibitory in low-sodium diet.

Activation of renal mechanosensory nerves is enhanced by high and suppressed by low sodium dietary intake. Afferent renal denervation results in salt-sensitive hypertension, suggesting that activation of the afferent renal nerves contributes to water and sodium balance. Another model of salt-sensitive hypertension is the endothelin B receptor (ETBR)-deficient rat. ET and its receptors are present in sensory nerves. Therefore, we examined whether ET receptor blockade altered the responsiveness of the renal sensory nerves. In anesthetized rats fed high-sodium diet, renal pelvic administration of the ETBR antagonist BQ-788 reduced the afferent renal nerve activity (ARNA) response to increasing renal pelvic pressure 7.5 mmHg from 26+/-3 to 9+/-3% and the PGE2-mediated renal pelvic release of substance P from 9+/-1 to 3+/-1 pg/min. Conversely, in rats fed low-sodium diet, renal pelvic administration of the ETAR antagonist BQ-123 enhanced the ARNA response to increased renal pelvic pressure from 9+/-2 to 23+/-6% and the PGE2-mediated renal pelvic release of substance P from 0+/-0 to 6+/-1 pg/min. Adding the ETAR antagonist to ETBR-blocked renal pelvises restored the responsiveness of renal sensory nerves in rats fed a high-sodium diet. Adding the ETBR antagonist to ETAR-blocked pelvises suppressed the responsiveness of the renal sensory nerves in rats fed a low-sodium diet. In conclusion, activation of ETBR and ETAR contributes to the enhanced and suppressed responsiveness of renal sensory nerves in conditions of high- and low-sodium dietary intake, respectively. Impaired renorenal reflexes may contribute to the salt-sensitive hypertension in the ETBR-deficient rat.

Animals↗

PubMed1999

Resting metabolic rate and thermogenic effect of food in vegetarian diets compared with Mediterranean diets.

The purpose of our work is to compare the resting metabolic rate (RMR) and thermogenic effect of food (TEF) in a group of vegetarians and a group of subjects consuming a Mediterranean diet. The composition of the diets was similar. Thirty-two subjects were studied: 16 vegetarians (age 34 +/- 9 years, BMI 21 +/- 2) and 16 omnivors (age 30 +/- 5 years, BMI 22 +/- 3). All were in excellent general health. Each subject consumed a dish of pasta (100 g) and bread (30 g) after RMR had been measured. TEF was measured over the next 3 h and calculated as the incremental area above RMR. Energy (vegetarians and omnivors 7,727 +/- 3,516 vs 8,970 +/- 2,273 kJ/day, respectively) and carbohydrate (vegetarians and omnivors 285.1 +/- 141.3 vs. 300.1 +/- 74 g/day, respectively) intakes of the 2 groups were similar. The vegetarian group consumed a higher quantity of fiber (30.5 +/- 16.7 vs. 16.5 +/- 7.9) and a lower amount of protein (44.9 +/- 18.3 vs. 70.1 +/- 14.9) than the omnivorous group. No significant differences were observed in RMR (4.23 +/- 0.96 vs. 4.06 +/- 0.54 kJ/min) and TEF (0.50 +/- 0.25 vs. 0.38 +/- 0.25 Delta kJ/min) between the groups. Results did not change after correcting for weight, age and gender. Our study failed to show any significant differences in RMR and TEF between vegetarians and subjects consuming a Mediterranean diet. We conclude that vegetarianism per se is not accompanied by a difference in RMR and TEF when the carbohydrate content of the diet is similar to a control group of nonvegetarians.

Adult↗

PubMed1998

Study of serum leptin in cafeteria-diet-overfed rats. Influence of diet, insulin and corticosterone.

In a group of 15 male Wistar rats overfed with cafeteria foods (delivering a mean fat percentage of 60%) during 5 months from the age of 8 weeks and in a control group of 15 rats fed with a standard chow for the same period, serum leptin, insulin and corticosterone were measured by RIA and body composition was determined by dual-energy X-ray absorptiometry. Significantly higher fasting serum concentrations of leptin, insulin and corticosterone were found in the cafeteria-diet group. Fasting leptin concentrations were significantly higher in rats with a body fat percentage of more than 25% compared to the others, irrespective of the type of feeding. The log serum leptin correlated positively with body fat percentage and fasting insulin concentration but not with corticosterone concentration. Leptin concentration corrected for body fat mass was, however, comparable between the two diet groups, while the leptin/insulin ratio was lower in the cafeteria-diet group. In conclusion, chronic overfeeding resulting in an increased body fat percentage in rats is associated with hyperleptinemia, hyperinsulinemia and hypercorticism. Serum leptin levels appear to primarily track total body fat percentage and are unaffected by dietary fat manipulation in cafeteria-diet-induced obese rats.

Absorptiometry, Photon↗

PubMed1981

Protein evaluation of mixed diets. Comparative study in man and in the pig and rat of vegetable-animal and vegetable protein diets.

The procedure suggested by FAO/WHO to evaluate the protein quality of mixed diets has been tested using vegetable and vegetable-animal protein diets. Chemical scores were calculated and protein digestibilities were compared in human adult, growing pigs and rats. Pigs were studied as alternatives to rats in the protein evaluation of human diets. The results showed that the choice of the samples to calculate the chemical score is important; that the composition of the samples for biological evaluations must be considered in order to avoid experimental problems, and that values for true protein digestibility in human subjects, pigs and rats are in agreement, and further studies of growing pigs as an experimental model are suggested. Minor differences in protein quality of the two diets were demonstrated.

Adult↗

PubMed1991

Diet patterns and health problems: diet in southern Europe.

The diet of the populations in southern Europe, particularly those living in the Mediterranean areas, was characterized by a relatively higher consumption of fish, olive oil, vegetables and fruit and by a lower consumption of meat and animal fat. In terms of nutrients the most significant difference between the Mediterranean type of diet and the diet of continental and northern European populations was in the consumption of saturated and monounsaturated fatty acids and to a lesser degree in the intake of protein, sugar and alcohol, as well as in regard to the dietary fiber content. Since the Mediterranean populations have shown a lower total mortality rate as well as a specific mortality from coronary heart disease (CHD) which in part could be explained by their dietary habits, the Mediterranean diet has often been proposed as a prototype on which dietary measures for the prevention of CHD in populations should be developed. However, more recent data indicate that in the last 20 years the food pattern of the Mediterranean populations was subjected to substantial changes, particularly in regard to the increase in meat and dairy product consumption which in turn has resulted in an increase in the percentage of energy of saturated fats and which has also affected the ratio of monounsaturated to saturated fatty acids. These changes have also affected some of the risk factors of CHD in those populations.

Diet↗

PubMedDate not supplied

Plant-based diet, serum fatty acid profile, and free radicals in postmenopausal women: the diet and androgens (DIANA) randomized trial.

High calorie and fat consumption and the production of free radicals are two major mechanistic pathways between diet and disease. In this study we evaluated the effect of a plant-based diet poor in animal fat and rich in (n-3) fatty acids on fatty acids of serum phospholipids and on the production of reactive oxygen metabolites (ROMs). One hundred and four healthy female postmenopausal volunteers were recruited and randomized to a dietary intervention or a control group. Dietary intervention included a program of food education and biweekly common meals for 18 weeks. When the intervention and control groups were compared, it was seen that dietary intervention resulted in a significant reduction of saturated fatty acids (-1.5%) and a significant increase in (n-3) fatty acids (+20.6%), in particular docosahexaenoic acid (+24.8%). We observed that arachidonic acid decreased (-7.7%), while (n-6) fatty acids did not, and the (n-3)/(n-6) polyunsaturated ratio increased significantly (+24.1%). As expected, ROMs decreased significantly in the intervention group (-6%). The results indicated that a plant-based diet can improve the serum fatty acid profile and decrease ROMs production. These results suggest that a plant-based diet may reduce the body's exposure to oxidative stress.

Aged↗

PubMed2003

Adolescence and the diet-dieting disparity: healthy food choice or risky health behaviour?

OBJECTIVES: Food choice in schoolchildren was examined in relation to dieting and measures of eating psychopathology. It was predicted that dieters would make healthier food choices compared to non-dieters and that measures of eating psychopathology would be associated with food choice. DESIGN: A cross-sectional questionnaire design incorporating an established adapted recall method was used to assess patterns of food consumption. METHODS: Questionnaires were administered in 13 state secondary schools. Measures included a food frequency questionnaire, the Children's Eating Attitudes Test (CHEAT), body satisfaction ratings, dietary restraint, and questions about dieting status. The sample consisted of 574 females and 445 males aged 11-16 years. RESULTS: Females made significantly more healthy food choices compared to males. Females reported dieting more than males (35% vs. 18%, respectively), and female dieters made more healthy food choices than female non-dieters. Almost a fifth (19%) of the entire sample reported skipping breakfast, with female dieters being three times more likely to do so than non-dieters. There were small but significant associations between reported food consumption and measures of eating attitudes, body dissatisfaction and restraint. For females who scored in the at-risk range on the CHEAT (8.7%), these associations were more substantial. CONCLUSIONS: Female dieters appear to make more healthy food choices than non-dieters and so may be tuning into healthy eating messages more effectively. Vulnerable females may use 'healthy eating' to hide risky weight reduction behaviours. Further studies are required to examine the nutritional impact of moderate and extreme dieting in this age group.

Adolescent↗

PubMed1994

Food-containing hypocaloric diets are as effective as liquid-supplement diets for obese individuals with NIDDM.

OBJECTIVE: This study was designed to determine if food-containing hypocaloric diets are as effective as liquid-supplement diets in promoting weight loss for obese individuals with non-insulin-dependent diabetes mellitus (NIDDM). RESEARCH DESIGN AND METHODS: Forty NIDDM subjects with body mass indexes (BMIs) of 30-40 kg/m2 were randomized to one of two 800-kcal diets for 12 weeks. Group A received liquid supplement only, and group B received supplement plus an evening meal. Both groups received an intensive behavioral education program. RESULTS: Weight loss and improvements in glycemic, blood lipid, and blood pressure parameters were similar for the two groups. Weight loss averaged 15.7 kg for the entire group. The need for insulin, anti-diabetes, and anti-hypertensive medication decreased significantly. No serious side effects were observed. CONCLUSIONS: Both food-containing and supplement diets providing 800 kcal a day effectively promote weight loss for obese individuals with NIDDM.

Body Mass Index↗

PubMed2006

Non-alcoholic fatty liver disease and the metabolic syndrome: effects of weight loss and a review of popular diets. Are low carbohydrate diets the answer?

Non-alcoholic fatty liver disease (NAFLD) encompasses a wide spectrum of fat-induced liver injury, ranging from relatively benign steatosis to cirrhosis and liver failure. The presence of obesity and insulin resistance is strongly associated with non-alcoholic fatty liver and confers on it a greater risk of histologically advanced disease. There is a growing concern in the medical profession as the prevalence of this disease continues to rise in parallel with the rise in obesity and the metabolic syndrome. Treatment options are limited and dietary weight loss is often advised. Low fat diets are difficult to adhere to and recent studies have shown the potential of low carbohydrate diets for weight loss and improving insulin resistance. Thus far, no study has evaluated the effect of low carbohydrate diets on NAFLD. Future studies will be required to address this question and others with regards to the nutritional adequacy and long-term side effects of these diets.

Diet↗

PubMed1990

Deleterious effects of high magnesium diets and beneficial effects of high potassium diets in hypertensive stroke-prone rats.

The effect of varying amounts of dietary magnesium (Mg) in conjunction with potassium (K) on hypertension and stroke mortality in hypertensive stroke-prone (SHRsp) rats was studied. These results show that high K (2.1%) diets strongly protect against stroke mortality and rises of blood pressure, while high Mg (0.26%) diets appeared to increase stroke mortality and accelerate the rise of blood pressure in SHRsp rats. Similarly, medium high (1.3%) levels of K in the diet significantly reduced blood pressure and stroke mortality but not nearly as much as the 2.1% K in the high K diet.

Animals↗

PubMed1989

Twenty-four hour excretion of urinary C-peptide in gestational diabetic women before and after treatment with diet or diet and insulin.

24-h urinary C-peptide excretion was studied in 119 women with gestational diabetes before and after treatment with diet or diet and insulin. The 24-h urinary C-peptide excretion in normal-weight gestational diabetic women at diagnosis was also compared to that of a healthy reference group. There was a wide variation in urinary C-peptide values which tended to be higher in normal-weight women with gestational diabetes at diagnosis compared to the reference group, but it did not reach statistical significance. Post partum gestational diabetic women had significantly higher urinary C-peptide excretion (p less than 0.002) than the reference group, indicating insulin resistance in women with gestational diabetes at this time. In 29 overweight women with gestational diabetes 24-h urinary C-peptide excretion did not significantly differ from that in normal-weight women with gestational diabetes. In 32 women with a more marked deviation in glucose tolerance (area greater than or equal to 46 mmol/l) 24-h urinary C-peptide values were significantly (p less than 0.05) higher than in 58 women with gestational diabetes with an area between 42 and 45.9 mmol/l. Both treatment alternatives, diet and diet plus insulin, significantly reduced postprandial blood glucose values (p less than 0.05) and urinary C-peptide excretion was significantly decreased (p less than 0.05).

Adult↗

PubMed1995

No adverse effects on growth seen in Scottish school children consuming either low fat diets or diets relatively high in non-starch polysaccharide.

This paper reports whether diets relatively high in non-starch polysaccharide (NSP) or those which meet Dietary Reference Values for percentage energy from fat are associated with poor growth and anthropometric status. Children aged seven to eight years (n = 136) were recruited from five schools in and around Edinburgh, selected randomly by Lothian Region's Education Department. Dietary intakes were estimated by their parents, using the seven day weighed inventory method. Height and weight were measured twice, with an interval of approximately 12 months, and expressed as standard deviation scores of 1990 UK population standards. There were no significant differences in mean height, weight, body mass index and height velocity between those children whose diets were relatively high in NSP or low in percentage energy from fat compared to the remainder of the sample. In addition, using multiple regression analysis, no associations were seen between growth and low fat diets or between growth and higher fibre diets. These results suggest that the low fat, higher fibre message can be applied to young children. However, further research is required to ensure that the results found in this sample apply to other groups of children.

Anthropometry↗

PubMed2026

Long-term microbiome and clinical effects of a microbiome-guided personalized diet versus low-FODMAP diet in irritable bowel syndrome: A 12-month follow-up randomized controlled trial.

Dietary therapy is central to irritable bowel syndrome (IBS) management, yet the long-term durability of the low-FODMAP diet (LFD), and of microbiome-guided personalization, remains unclear. We assessed the long-term clinical and gut-microbiome effects of a microbiome-guided personalized diet (PD) compared with a standard LFD in adults meeting Rome IV criteria for IBS. In this multicenter, open-label randomized controlled trial with blinded outcome assessment, participants who completed a 6-week dietary intervention (PD or LFD) were followed at 6 and 12 months without further dietary intervention. Outcomes included the IBS Severity Scoring System (IBS-SSS), IBS Quality of Life (IBS-QOL), and the Hospital Anxiety and Depression Scale (HADS); gut microbiota were profiled by 16S rRNA sequencing. Longitudinal changes were evaluated using linear mixed-effects models, responder analyses, PERMANOVA, and PERMDISP. Both diets reduced IBS-SSS at 6 weeks. PD maintained symptom improvement at 6 and 12 months (-82.0 and -78.3 points from baseline), whereas LFD benefits regressed by 12 months (+29.3 points; between-group p = 0.001). At 12 months, IBS-SSS responder rates were higher with PD than LFD (62.5% vs 34.5%; absolute risk difference +28.0%, 95% CI 4.2-47.7; Fisher p = 0.029), and IBS-QOL, HADS-anxiety, and HADS-depression showed more favourable trajectories with PD. PD was associated with sustained Shannon alpha-diversity gains (+0.488 at 6 weeks; +0.205 at 12 months; both p < 0.01). A modest between-group beta-diversity difference at 6 months (R2 = 0.035; p = 0.011) was not significant at 12 months. This hypothesis-generating follow-up suggests more durable benefit with PD; larger trials powered for long-term clinical and microbiome outcomes are warranted.

Humans↗