Habitual Fat Intake Research Articles

Burnout, Fat Intake, and Body Mass Index in Health Professionals Working in a Public Hospital: A Cross-Sectional Study.

Burnout can have a negative influence on dietary intake, promoting unhealthy eating behaviors in health care workers. This study determined the association between burnout, saturated fat intake, and body mass index (BMI) in a group of health care workers. A cross-sectional study was conducted in 300 health professionals residing in Rioja, Department of San Martin, Peru. Data were collected through an online and face-to-face survey. Burnout was assessed using a scale adapted and validated in the Peruvian population. Additionally, a validated food frequency questionnaire (FFQ) was used to assess habitual fat intake. Both instruments were validated and adapted to the Peruvian population. Data were analyzed using Pearson correlation coefficients and multivariate logistic regression. Values of P < .05 were considered statistically significant. In the adjusted model, it was found that, for each extra point on intake scale, an average of 1.10 (95% CI, 0.57-1.62, P < .001) points increased burnout scale; these results persisted when compared by gender, 1.17 0.49 1.85, and 1.08 0.16 2.00, respectively female male genders. there no association between bmi (P > .05). Future programs and interventions should be considered to minimize the effects of burnout on unhealthy food intake in health care workers in Peru to ensure better medical care by health care professionals on behalf of patients.

Sarcopenia and Appendicular Muscle Mass as Predictors of Impaired Fasting Glucose/Type 2 Diabetes in Elderly Women.

Elderly women exhibit a high risk of type 2 diabetes (T2D), but no definitive data exist about the possible role of postmenopausal increases in visceral adiposity, the loss of lean body mass, or decreases in the sum of the lean mass of arms and legs (appendicular skeletal muscle mass (ASMM)). This retrospective, longitudinal study investigated whether body composition (bioelectrical impedance analysis) predicted the development of impaired fasting glucose (IFG) or T2D in a cohort of 159 elderly women (age: 71 ± 5 years, follow-up: 94 months) from southern Italy (Clinical Nutrition and Geriatric Units of the “Mater Domini” University Hospital in Catanzaro, Calabria region, and the “P. Giaccone ”University Hospital in Palermo, Sicily region). Sarcopenia was defined in a subgroup of 128 women according to the EWGSOP criteria as the presence of low muscle strength (handgrip strength <16 kg) plus low muscle mass (reported as appendicular skeletal muscle mass <15 kg). Participants with a low ASMM had a higher IFG/T2D incidence than those with a normal ASMM (17% vs. 6%, p-adjusted = 0.044); this finding was independent of BMI, fat mass, waist circumference, and habitual fat intake (OR = 3.81, p = 0.034). A higher incidence of IFG/T2D was observed in the subgroup with sarcopenia than those without sarcopenia (33% vs. 7%, p-adjusted = 0.005) independent of BMI and fat mass (OR = 6.75, p = 0.007). In conclusion, this study demonstrates that elderly women with low ASMM had a higher probability of developing IFG/T2D. Further studies are needed to confirm these results in men and in other age groups.

The Effect of Habitual Fat Intake, IL6 Polymorphism, and Different Diet Strategies on Inflammation in Postmenopausal Women with Central Obesity.

The hypothesis that habitual fat intake, the IL6 genotype, the Mediterranean diet or the central European diet for 16 weeks affect biomarkers of inflammation in centrally obese postmenopausal women, was tested in a randomized controlled trial. Dietary intake was assessed using a three-day food diary. Lipid parameters were measured using a Beckman Coulter AU analyzer. Transcription of TNF and IL6 genes was analyzed in peripheral blood mononuclear cells using real-time PCR. Concentrations of tumor necrosis factor alpha (TNFα) and interleukin 6 (IL6) were measured with ELISA. rs1800795 polymorphism of IL6 was analyzed using hydrolyzing probes. Higher energy intake from fat was associated with higher IL6 levels (p < 0.05). Significantly (p < 0.01) lower total cholesterol (T-C) and low-density lipoprotein cholesterol (LDL-C) concentrations were observed in the GG IL6 rs1800795 genotype group. Both diets significantly (p < 0.001) decreased TNFα concentrations. Neither IL6 gene transcription levels nor blood IL6 concentrations were affected by them. Our findings confirm that habitual fat intake may affect inflammation. The rs1800795 IL6 polymorphism alone did not significantly affect body weight or body composition in aimed group, but C-allele carriers had higher levels of T-C and LDL-C. This polymorphism did not affect inflammation. Both diets may lead to a decrease in TNFα concentration.

Fat Taste Sensitivity Is Associated with Short-Term and Habitual Fat Intake.

Evidence suggests individuals less sensitive to fat taste (high fat taste thresholds (FTT)) may be overweight or obese and consume greater amounts of dietary fat than more sensitive individuals. The aims of this study were to assess associations between FTT, anthropometric measurements, fat intake, and liking of fatty foods. FTT was assessed in 69 Australian females (mean age 41.3 (15.6) (SD) years and mean body mass index 26.3 (5.7) kg/m2) by a 3-alternate forced choice methodology and transformed to an ordinal scale (FT rank). Food liking was assessed by hedonic ratings of high-fat and reduced-fat foods, and a 24-h food recall and food frequency questionnaire was completed. Linear mixed regression models were fitted. FT rank was associated with dietary % energy from fat ( = 0.110 [95% CI: 0.003, 0.216]), % energy from carbohydrate ( = −0.112 [−0.188, −0.035]), and frequency of consumption of foods per day from food groups: high-fat dairy ( = 1.091 [0.106, 2.242]), meat & meat alternatives ( = 0.669 [0.168, 1.170]), and grain & cereals ( = 0.771 [0.212, 1.329]) (adjusted for energy and age). There were no associations between FT rank and anthropometric measurements or hedonic ratings. Therefore, fat taste sensitivity appears to be associated with short-term fat intake, but not body size in this group of females.

Duodenal fatty acid sensor and transporter expression following acute fat exposure in healthy lean humans

Free fatty acids (FFAs) and their derivatives are detected by G-protein coupled receptors (GPRs) on enteroendocrine cells, with specific transporters on enterocytes. It is unknown whether acute fat exposure affects FFA sensors/transporters, and whether this relates to hormone secretion and habitual fat intake. We studied 20 healthy participants (10M, 10F; BMI: 22±1kg/m2; age: 28±2 years), after an overnight fast, on 2 separate days. On the first day, duodenal biopsies were collected endoscopically before, and after, a 30-min intraduodenal (ID) infusion of 10% Intralipid®, and relative transcript expression of FFA receptor 1 (FFAR1), FFA receptor 4 (FFAR4), GPR119 and the FFA transporter, cluster of differentiation-36 (CD36) was quantified from biopsies. On the second day, ID Intralipid® was infused for 120-min, and plasma concentrations of cholecystokinin (CCK) and glucagon-like peptide-1 (GLP-1) evaluated. Habitual dietary intake was assessed using food frequency questionnaires (FFQs). ID Intralipid® increased expression of GPR119, but not FFAR1, FFAR4 and CD36, and stimulated CCK and GLP-1 secretion. Habitual polyunsaturated fatty acid (PUFA) consumption was negatively associated with basal GPR119 expression. GPR119 is an early transcriptional responder to duodenal lipid in lean humans, although this response appeared reduced in individuals with high PUFA intake. These observations may have implications for downstream regulation of gut hormone secretion and appetite. This study was registered as a clinical trial with the Australia and New Zealand Clinical Trial Registry (Trial number: ACTRN12612000376842).

Cognitive control over visual food cue saliency is greater in reduced-overweight/obese but not in weight relapsed women: An EEG study

ObjectivePoor weight management may relate to a reduction in neurobehavioural control over food intake and heightened reactivity of the brain's neural reward pathways. Here we explore the neurophysiology of food-related visual cue processing in weight reduced and weight relapsed women by assessing differences in cortical arousal and attentional processing using a food-Stroop paradigm. Methods51 women were recruited into 4 groups: reduced-weight participants (RED, n=14) compared to BMI matched low-weight controls (LW-CTL, n=18); and weight relapsed participants (REL, n=10) compared to BMI matched high-weight controls (HW-CTL, n=9). Eating behaviour and body image questionnaires were completed. Two Stroop tasks (one containing food images, the other containing neutral images) were completed with record of electroencephalography (EEG). ResultsDifferences in cortical arousal were found in RED versus LW-CTL women, and were seen during food task execution only. Compared to their controls, RED women exhibited lower relative delta band power (p=0.01) and higher relative beta band power (p=0.01) over the right frontal cortex (F4). Within the RED group, delta band oscillations correlated positively with self-reported habitual fat intake and with body shape dissatisfaction. ConclusionsAs compared to women matched for phenotype but with no history of weight reduction, reduced-overweight/obese women show increased neurobehavioural control over external food cues and the inhibition of reward-orientated feeding responses. Insight into these self-regulatory mechanisms which attenuate food cue saliency may aid in the development of cognitive remediation therapies which facilitate long-term weight loss.

Relative validation of the dietary intake of fatty acids among adults in the Swedish National Dietary Survey using plasma phospholipid fatty acid composition.

The aims of a national dietary study are several-fold. One purpose is to monitor the intake of foods and nutrients in the population and to compare intakes with dietary recommendations. It is, however, difficult to measure dietary fat intake and plasma biomarker fatty acid (FA) composition may be used as an objective measure of dietary fat intake. Thus, the relative ability of a diet record to capture habitual fat intake was validated against biomarker FA. Dietary fat intake was measured in a novel self-assisted web-based 4-d food record - the 'Riksmaten' method. Spearman rank correlations between dietary FA, certain food groups (fish-shellfish, dairy products, meat and sausages, and spreads) and the fat content of these food groups and biomarker FA were explored. Participants were 150 women and 129 men, aged 18-80 years, who took part in the Swedish National Dietary Survey, Riksmaten adults 2010-11. Blood samples were collected on average 20 d after the diet record and FA composition was measured in plasma phospholipids by GLC. Total n-3 FA (r 0·31), EPA (r 0·34) and DHA (r 0·42) were correlated between plasma and diet (all P≤0·001). Adjustment for covariates attenuated the relationships. Linoleic acid was only marginally correlated (r 0·15; P=0·06) in women. Plasma pentadecaenoic acid and heptadecaenoic acid were correlated with dairy product intake as previously reported. In conclusion, the Riksmaten method appears valid for the purpose of collecting data on dietary fat composition, at least in a healthy adult population.

Habitual fat intake predicts memory function in younger women

High intakes of fat have been linked to greater cognitive decline in old age, but such associations may already occur in younger adults. We tested memory and learning in 38 women (25 to 45 years old), recruited for a larger observational study in women with polycystic ovary syndrome. These women varied in health status, though not significantly between cases (n = 23) and controls (n = 15). Performance on tests sensitive to medial temporal lobe function (CANTABeclipse, Cambridge Cognition Ltd, Cambridge, UK), i.e., verbal memory, visuo-spatial learning, and delayed pattern matching (DMS), were compared with intakes of macronutrients from 7-day diet diaries and physiological indices of metabolic syndrome. Partial correlations were adjusted for age, activity, and verbal IQ (National Adult Reading Test). Greater intakes of saturated and trans fats, and higher saturated to unsaturated fat ratio (Sat:UFA), were associated with more errors on the visuo-spatial task and with poorer word recall and recognition. Unexpectedly, higher UFA intake predicted poorer performance on the word recall and recognition measures. Fasting insulin was positively correlated with poorer word recognition only, whereas higher blood total cholesterol was associated only with visuo-spatial learning errors. None of these variables predicted performance on a DMS test. The significant nutrient–cognition relationships were tested for mediation by total energy intake: saturated and trans fat intakes, and Sat:UFA, remained significant predictors specifically of visuo-spatial learning errors, whereas total fat and UFA intakes now predicted only poorer word recall. Examination of associations separately for monounsaturated (MUFA) and polyunsaturated fats suggested that only MUFA intake was predictive of poorer word recall. Saturated and trans fats, and fasting insulin, may already be associated with cognitive deficits in younger women. The findings need extending but may have important implications for public health.

Habitual fat intake predicts cognitive function in young women

Habitual fat intake predicts cognitive function in young women

The role of vitamin E in the diet.

Abstract The last decade has seen many developments in our understanding of vitamin E, its transport and metabolism, and its potential role in the prevention of chronic disease. Of the eight fat-soluble substances comprising vitamin E, α-tocopherol has emerged as central to vitamin E activity in the body, its concentration in the plasma being governed by α-tocopherol transfer protein and maintained in a narrow range. Although new insights into the role of habitual fat intake in determining human requirements for vitamin E have been gained, uncertainties remain and estimates of requirements differ considerably between authorities. Investigation of the potential of this potent chain-breaking antioxidant to prevent or delay conditions thought to be associated with oxidative stress, including cardiovascular disease, cancer, Alzheimer's disease and Parkinson's disease, has challenged nutritionists to reconsider optimal intakes of vitamin E. High-dose supplementation has proved ineffective in reducing risk and may even be associated with increased risk; yet, new evidence suggests that a lifetime diet rich in α-tocopherol may provide protection against heart disease and cancer. Intakes of α-tocopherol are low in some western populations, which may in part be the result of advice to consume low-fat diets, intended to help address rising rates of obesity. An increased focus on fat quality, consistent with advice stemming from the cardiovascular literature, will help ensure adequate intakes of vitamin E in the context of diets moderate in total fat.

Potential of essential fatty acid deficiency with extremely low fat diet in lipoprotein lipase deficiency during pregnancy: A case report

BackgroundPregnancy in patients with lipoprotein lipase deficiency is associated with high risk of maternal pancreatitis and fetal death. A very low fat diet (< 10% of calories) is the primary treatment modality for the prevention of acute pancreatitis, a rare but potentially serious complication of severe hypertriglyceridemia. Since pregnancy can exacerbate hypertriglyceridemia in the genetic absence of lipoprotein lipase, a further reduction of dietary fat intake to < 1–2% of total caloric intake may be required during the pregnancy, along with the administration of a fibrate. It is uncertain if essential fatty acid deficiency will develop in the mother and fetus with this extremely low fat diet, or whether fibrates will cross the placenta and concentrate in the fetus.Case presentationA 23 year-old gravida 1 woman with primary lipoprotein lipase deficiency was seen at 7 weeks of gestation in the Lipid Clinic for management of severe hypertriglyceridemia that had worsened with pregnancy. While on her habitual fat intake of 10% of total calories, her pregnancy resulted in an exacerbation of the hypertriglyceridemia, which prompted further restriction of fat intake to < 2% of total calories, as well as administration of gemfibrozil at a lower than average dose. The level of gemfibrozil, as the active metabolite, in the venous and arterial fetal cord blood was within the expected therapeutic range for adults. The clinical signs and a biomarker of essential fatty acid deficiency, namely the ratio of 20:3 [n-9] to 20:4 [n-6] fatty acids, were closely monitored throughout her pregnancy. Despite her extremely low fat diet, the levels of essential fatty acids measured in the mother and in the fetal blood immediately postpartum were normal. Normal essential fatty acid levels may have been achieved by the topical application of sunflower oil.ConclusionsAn extremely low fat diet in combination with topical sunflower oil and gemfibrozil administration was safely implemented in pregnancy associated with the severe hypertriglyceridemia of lipoprotein lipase deficiency.

Relation between calcium intake and fat oxidation in adult humans.

To determine if total calcium (Ca(2+)) intake and intake of Ca(2+) from dairy sources are related to whole-body fat oxidation. : Cross-sectional study. A total of 35 (21 m, 14 f) non-obese, healthy adults (mean+/-s.d., age: 31+/-6 y; weight: 71.2+/-12.3 kg; BMI: 23.7+/-2.9 kg m(-2); body fat: 21.4+/-5.4%). Daily (24 h) energy expenditure (EE) and macronutrient oxidation using whole-room indirect calorimetry; habitual Ca(2+) intake estimated from analysis of 4-day food records; acute Ca(2+) intake estimated from measured food intake during a 24-h stay in a room calorimeter. Acute Ca(2+) intake (mg. kcal(-1)) was positively correlated with fat oxidation over 24 h (r=0.38, P=0.03), during sleep (r=0.36, P=0.04), and during light physical activity (r=0.32, P=0.07). Acute Ca(2+) intake was inversely correlated with 24-h respiratory quotient (RQ) (r=-0.36, P=0.04) and RQ during sleep (r=-0.31, P=0.07). After adjustment for fat mass, fat-free mass, energy balance, acute fat intake, and habitual fat intake, acute Ca(2+) intake explained approximately 10% of the variance in 24-h fat oxidation. Habitual Ca(2+) intake was not significantly correlated to fat oxidation or RQ. Total Ca(2+) intake and Ca(2+) intake from dairy sources were similarly correlated with fat oxidation. In backwards stepwise models, total Ca(2+) intake was a stronger predictor of 24 h fat oxidation than dairy Ca(2+) intake. Higher acute Ca(2+) intake is associated with higher rates of whole-body fat oxidation. These effects were apparent over 24 h, during sleep and, to a lesser extent, during light physical activity. Calcium intake from dairy sources was not a more important predictor of fat oxidation than total Ca(2+) intake.

Serum fatty acids, lipoprotein (a) and apolipoprotein profiles of middle-aged men and women in South Vietnam.

In Vietnam, increasing fat consumption is a trend recognized recently in urban areas. To obtain a reasonable nutrition status and prevent cardiovascular disease (CVD), it is necessary to obtain information on habitual fat intake and biochemical parameters as risk factors for CVD in Vietnamese populations. Therefore, from the analysis of serum fatty acid composition, fat consumption patterns in Vietnamese populations in South Vietnam, with different incomes, are discussed in this study. In addition, some risk factors for premature CVD, serum lipoprotein (a) and apolipoprotein concentrations are also assessed in these Vietnamese populations. The study was carried out in men and women aged 40-59 in three different districts: urban (n = 100), suburban (n = 98) and rural (n = 98). The results of serum fatty acid composition analysis reflected differences in quality fat intake among the three populations. The urban population was estimated to consume more vegetable oil but less fish than their rural counterparts. Although serum lipoprotein (a) and apolipoprotein B levels were below the ranges associated with atherogenesis, ongoing attention to dietary fat intake for the prevention of CVD in Vietnamese populations is required.

Nutritional influences on cognitive function: mechanisms of susceptibility

The impact of nutritional variation, within populations not overtly malnourished, on cognitive function and arousal is considered. The emphasis is on susceptibility to acute effects of meals and glucose loads, and chronic effects of dieting, on mental performance, and effects of cholesterol and vitamin levels on cognitive impairment. New developments in understanding dietary influences on neurohormonal systems, and their implications for cognition and affect, allow reinterpretation of both earlier and recent findings. Evidence for a detrimental effect of omitting a meal on cognitive performance remains equivocal: from the outset, idiosyncrasy has prevailed. Yet, for young and nutritionally vulnerable children, breakfast is more likely to benefit than hinder performance. For nutrient composition, despite inconsistencies, some cautious predictions can be made. Acutely, carbohydrate-rich-protein-poor meals can be sedating and anxiolytic; by comparison, protein-rich meals may be arousing, improving reaction time but also increasing unfocused vigilance. Fat-rich meals can lead to a decline in alertness, especially where they differ from habitual fat intake. These acute effects may vary with time of day and nutritional status. Chronically, protein-rich diets have been associated with decreased positive and increased negative affect relative to carbohydrate-rich diets. Probable mechanisms include diet-induced changes in monoamine, especially serotoninergic neurotransmitter activity, and functioning of the hypothalamic pituitary adrenal axis. Effects are interpreted in the context of individual traits and susceptibility to challenging, even stressful, tests of performance. Preoccupation with dieting may impair cognition by interfering with working memory capacity, independently of nutritional status. The change in cognitive performance after administration of glucose, and other foods, may depend on the level of sympathetic activation, glucocorticoid secretion, and pancreatic beta-cell function, rather than simple fuelling of neural activity. Thus, outcomes can be predicted by vulnerability in coping with stressful challenges, interacting with nutritional history and neuroendocrine status. Functioning of such systems may be susceptible to dietary influences on neural membrane fluidity, and vitamin-dependent cerebrovascular health, with cognitive vulnerability increasing with age.

Habitual fat intake and basal fat oxidation in obese and non-obese Caucasians.

To examine the relationship between habitual fat intake and basal fat oxidation in obese and non-obese Caucasian men and women. Habitual fat intake was assessed by 7-day weighed dietary records and resting fat oxidation was determined after an overnight fast in 132 weight stable non-diabetic subjects (38 males, 94 females). All subjects were characterized for weight, height, waist-to-hip ratio, physical activity, plasma glucose and insulin response to an oral glucose load, plasma catecholamine and leptin levels. Under-reporters, defined according to plausibility of the relationship between energy expenditure and energy intake, were excluded from the analyses. The mean age was 53.1+/-10.6 y (19-72 y) and mean body mass index (BMI) was 30.7+/-5.8 kg/m(2) (19.4-45.8 kg/m(2)). Sixty-eight subjects were obese (BMI>30 kg/m(2)). Univariate regression analysis revealed a significant, albeit modest, relationship between absolute fat intake and BMI (r(2)=0.06; P<or=0.05) but not between fat intake and fat mass (r(2)=0.026; P=0.08). However, multiple regression analysis revealed significant effects of body fat mass (FM) and sex on basal fat oxidation (bFO) explaining 33% of the variation of bFO (P<or=0.0001; radical s.e.=18.0 g/24 h). In univariate regression analysis, habitual fat intake was significantly related to adjusted fat oxidation, explaining 12% of the variation (P<or=0.0001; radical s.e.=11.7 g/24 h). Habitual fat intake has a significant, albeit modest, effect on basal fat oxidation, even when adjusted for sex and body FM. The rather modest effect of habitual fat intake on fat oxidation may in part explain the increased propensity to gain FM on a high-fat diet.

Food Choice and Fat Intake of Adolescents and Adults: Associations of Intakes within Social Networks

Background.Influences of the social environment are important in determining eating behavior. Family influences have been demonstrated by resemblances in intakes within families, but research on resemblance in intake between friends is lacking. We investigated the resemblance in fat and food intake within social networks that included family members and peers.Methods.Fat consumption was assessed with a food frequency questionnaire in 361 social networks consisting of 15-year-old adolescents (n= 347), their mothers (n= 309), their fathers (n= 270), their friends (n= 240), 79 friends of mothers, and 29 friends of fathers. Ten family interviews and four focus group interviews were carried out in a subsample.Results.Within the nuclear family, the intake of 76 to 94% of the foods was significantly associated, which resulted in moderate Pearson correlations for fat and fatty acid intake (% of energy intake) between parents (0.30–0.34), between mother and child (0.19–0.38), and between father and child (0.16–0.26). No significant correlations for fat intake were found between friends, but the consumption of specific foods was related.Conclusions.We found clear resemblance in habitual fat and food intake between parents and their adolescent children and between spouses. Friends do not seem to have a lot of influence on the fat intake of adolescents and adults in this population.

The adaptation of nutrient oxidation to nutrient intake on a high-fat diet

Intervention studies have shown that the adaptation of fat oxidation to fat intake, when changing the dietary fat content, is not abrupt. This study was conducted to measure the time course of adaptation of oxidation rates to increases in the fat content of the diet, when feeding subjects at energy balance. Twelve healthy, non-obese males and females (age: 26 +/- 2, BMI: 21.4 +/- 0.5, habitual fat intake: 29 +/- 1% energy) consumed a low-fat diet for 6 days (days 1-6) followed by a high-fat diet for 7 days (day 7-13). Days 5-9 and day 13 were spent in a respiration chamber. After adjusting energy intake to 24h energy expenditure on day 5, subjects were in energy balance (range -0.15 to +0.23 kJ/day) on days 6-9 and day 13. Fat balance was zero on day 6 but became positive after changing to the high-fat diet (1.06 +/- 0.15, 0.75 +/- 0.15, and 0.55 +/- 0.14 MJ/day for days 7, 8, and 9 respectively, p. < 0.05), reaching a new balance on day 13, 7 days afterwards. Thus, in case of energy balance, lean subjects are capable of adjusting fat oxidation to fat intake within 7 days, when dietary fat content is increased.

Changes in fat oxidation in response to a high-fat diet

Intervention studies have shown that the adaptation of fat oxidation to fat intake, when the dietary fat content is changed, is not abrupt. This study was conducted to measure the time course of adaptation of oxidation rates to increases in the fat content of the diet while subjects were fed at energy balance. Twelve healthy, nonobese males and females [age: 26 +/- 2 y, body mass index (in kg/m2): 21.4 +/- 0.5; and habitual fat intake: 29 +/- 1% of energy] consumed a low-fat diet for 6 d (days 1-6) followed by a high-fat diet for 7 d (days 7-13). Days 5-9 and 13 were spent in a respiration chamber. After adjustment for energy intake to 24-h energy expenditure on day 5, subjects were in energy balance (range: -0.15 to 0.23 kJ/d) on days 6-9 and 13. Fat balance was zero on day 6 but became positive after subjects changed to the high-fat diet (1.06 +/- 0.15, 0.75 +/- 0.15, and 0.55 +/- 0.14 MJ/d for days 7, 8, and 9, respectively, P < 0.05), reaching a new balance on day 13, 7 d afterward. In conclusion, when in energy balance, lean subjects are capable of adjusting fat oxidation to fat intake within 7 d of when dietary fat content is increased.

Effect of diet composition on leptin concentration in lean subjects

The recently discovered leptin is thought to be a satiety signal regulating food intake. In mice, it has been shown that on a high-fat diet leptin concentration increases, but the increase was explained by increased fat mass. It is yet unknown whether leptin is influenced by other nutritional factors. Here, leptin levels were measured in human volunteers on a high-fat diet, while maintaining energy balance. Twelve healthy, non-obese males and females (age, 26 ± 2 years; 21.4 ± 0.5 body mass index, habitual fat intake, 29 ± 1 energy % [en%]) consumed a high-fat diet (60 en% fat) for 7 days (days 1 to 7). Subjects were in energy balance (range, −0.15 to +0.23 MJ/d) as measured in a respiration chamber on days 1 to 3 and 7. Fasting baseline plasma leptin concentrations correlated with body fat percentage ( R 2 = .64, P < .005). On average, no changes in leptin concentration on the high-fat diet were observed. However, on an individual basis, changes in leptin concentrations in response to the high-fat diet correlated with changes in insulin concentrations. In conclusion, in the case of energy balance, short-term changes in diet composition have no effect on fasting leptin concentration in lean subjects.