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Biomedical subjects

J E Blundell

Publications and source records attributed to J E Blundell.

At least 19 recordsLinked to original sources
PubMed2002

The effect of graded levels of exercise on energy intake and balance in free-living women.

AIM: We assessed the effect of graded increases in exercised-induced energy expenditure (EE) on appetite, daily energy intake (EI), total daily EE and body weight in six lean women using a within-subject, repeated measures design. METHOD: Subjects were each studied three times during 7 day treatments, corresponding to no-exercise (control; Nex; 0 MJ/day), medium exercise level (Mex; approximately 1.9 MJ/day) and high exercise level (Hex; approximately 3.4 MJ/day), with 2 day maintenance beforehand. Subjects self-weighed ad libitum food intake. EE was assessed by continual heart rate monitoring. During waking hours subjects recorded hourly sensations of hunger and appetite. RESULTS: EE amounted to 9.2, 11.0 and 12.1 MJ/day (F (2, 10)=5.67; P=0.023 (s.e.d.=0.87)) on the Nex, Mex and Hex treatments, respectively. The corresponding values for EI were 8.9, 9.2 and 10.0 MJ/day (F (2, 10)=4.80; P=0.035 (s.e.d.=0.36)). There were very weak treatment effects on hunger. Weight loss was significantly different from zero on the Mex and Hex treatments. CONCLUSION: Markedly increasing EE through exercise produced significant but partial compensations in EI ( approximately 33% of EE due to exercise). Accurate adjustments of El to acute increases in EE are likely to take weeks rather than days.

Adult↗
PubMed2002

Differences in postprandial responses to fat and carbohydrate loads in habitual high and low fat consumers (phenotypes).

The present study investigated metabolic responses to fat and carbohydrate ingestion in lean male individuals consuming an habitual diet high or low in fat. Twelve high-fat phenotypes (HF) and twelve low-fat phenotypes (LF) participated in the study. Energy intake and macronutrient intake variables were assessed using a food frequency questionnaire. Resting (RMR) and postprandial metabolic rate and substrate oxidation (respiratory quotient; RQ) were measured by indirect calorimetry. HF had a significantly higher RMR and higher resting heart rate than LF. These variables remained higher in HF following the macronutrient challenge. In all subjects the carbohydrate load increased metabolic rate and heart rate significantly more than the fat load. Fat oxidation (indicated by a low RQ) was significantly higher in HF than in LF following the fat load; the ability to oxidise a high carbohydrate load did not differ between the groups. Lean male subjects consuming a diet high in fat were associated with increased energy expenditure at rest and a relatively higher fat oxidation in response to a high fat load; these observations may be partly responsible for maintaining energy balance on a high-fat (high-energy) diet. In contrast, a low consumer of fat is associated with relatively lower energy expenditure at rest and lower fat oxidation, which has implications for weight gain if high-fat foods or meals are periodically introduced to the diet.

Adult↗
PubMed2001

Description and evaluation of a Newton-based electronic appetite rating system for temporal tracking of appetite in human subjects.

This study assessed the reliability and validity of a palm-top-based electronic appetite rating system (EARS) in relation to the traditional paper and pen method. Twenty healthy subjects [10 male (M) and 10 female (F)] - mean age M=31 years (S.D.=8), F=27 years (S.D.=5); mean BMI M=24 (S.D.=2), F=21 (S.D.=5) - participated in a 4-day protocol. Measurements were made on days 1 and 4. Subjects were given paper and an EARS to log hourly subjective motivation to eat during waking hours. Food intake and meal times were fixed. Subjects were given a maintenance diet (comprising 40% fat, 47% carbohydrate and 13% protein by energy) calculated at 1.6xResting Metabolic Rate (RMR), as three isoenergetic meals. Bland and Altman's test for bias between two measurement techniques found significant differences between EARS and paper and pen for two of eight responses (hunger and fullness). Regression analysis confirmed that there were no day, sex or order effects between ratings obtained using either technique. For 15 subjects, there was no significant difference between results, with a linear relationship between the two methods that explained most of the variance (r(2) ranged from 62.6 to 98.6). The slope for all subjects was less than 1, which was partly explained by a tendency for bias at the extreme end of results on the EARS technique. These data suggest that the EARS is a useful and reliable technique for real-time data collection in appetite research but that it should not be used interchangeably with paper and pen techniques.

Adult↗
PubMed2001

Control of food intake in the obese.

Food intake (eating) is a form of behavior that is subject to conscious control. In practice, many obese and weight-gaining individuals claim that their eating is out of (their) control. Mechanistic models describe the interplay of biological and environmental forces that control food intake. However, because human food intake is characterized by individuals intervening to adjust their own patterns of behavior, food intake should reflect interactions among biology, environment, and attempted self-imposed control of behavior. In general, humans display a system of weight regulation that is asymmetrical--a reduction in body weight is strongly defended but weight gain is not. The body seems to tolerate a positive energy balance. There is no mechanism that can detect a positive energy balance per se or that can implement a sufficiently strong correction to behavior to maintain body weight in an environment that promotes consumption. The evolutionary process has favored biological traits associated with preferences for high energy density (sweet and/or fatty) energy-yielding foods. The control of food intake in obese or weight-gaining individuals may display various risk factors that favor an increase in energy. These include the preference for high energy-dense over low energy-dense foods, weak postprandial inhibitory signaling, strong hunger traits associated with low leptin levels after weight loss, and the consumption of fatty foods. In addition, many individuals (up to 47% of some samples) display binge eating patterns, whereas approximately 16% show either night eating or nocturnal eating. Because energy expenditure is only loosely coupled to energy intake, sedentariness does not down-regulate food intake.

Appetite Regulation↗
PubMed2001

High-fat and low-fat phenotypes: habitual eating of high- and low-fat foods not related to taste preference for fat.

OBJECTIVE: To characterize taste preferences in habitual high fat (HF) and low fat (LF) phenotypes. DESIGN: Eighteen test solutions to taste for each subject group in a fully repeated 2x6x3 measures design. SETTING: The Human Appetite Research Unit at Leeds University, Psychology Department. SUBJECTS: Eight lean HF (mean percentage fat intake 43.4% daily energy) and eight lean LF (mean percentage fat intake 32.7% daily energy) were recruited from the staff/student population of Leeds University. INTERVENTIONS: All subjects were required to taste 18 solutions based on six levels of fat content and three levels of sucrose content. Subjects rated each solution for fat content, sweetness and pleasantness. RESULTS: HF and LF showed significant effect for the fat content of the solution on the perception of creaminess (P<0.000), and sugar content on the perception of sweetness (P<0.000). HF and LF did not differ in their taste preferences and no preferred level of fat or sweetness was detected in either group. CONCLUSIONS: In young adult males, habitual food selection is not related to taste preference. SPONSORSHIP: This study was supported by the Biotechnology and Biological Sciences Research Council (BBSRC).

Adolescent↗
PubMed2001

Regulation of appetite: role of leptin in signalling systems for drive and satiety.

BACKGROUND: The healthy regulation of appetite involves a balance between excitatory (drive) and inhibitory (satiety) processes. For many years research has concentrated on the identification of signalling systems that mediate satiety to the relative exclusion of drive-inducing biological events. However, the so-called long-term regulation of body weight has recently been given substance by the identification of a chemical signal believed to link the brain with adipose tissue stores. ANALYSIS: This signal, leptin, is in position to modulate the expression of a drive to eat. Studies on the relationship between leptin and perceived hunger, and on the eating behaviour of leptin-deficient individuals, are consistent with the intervention of leptin in a drive system. The contrast between the roles of leptin and serotonin in appetite regulation reflects the difference between drive-signalling and satiety signalling processes. CONCLUSION: It is proposed that leptin modulates the drive signals arising from the metabolic demand for energy but also shows some properties of a post-prandial satiety signal.

Animals↗
PubMed2001

SB-334867, a selective orexin-1 receptor antagonist, enhances behavioural satiety and blocks the hyperphagic effect of orexin-A in rats.

Intracerebroventricular (i.c.v.) administration of the novel hypothalamic neuropeptide orexin-A stimulates food intake in rats, and delays the onset of behavioural satiety (i.e. the natural transition from feeding to resting). Furthermore, preliminary findings with the selective orexin-1 receptor antagonist, SB-334867, suggest that orexin-A regulation of food intake is mediated via the orexin-1 receptor. At present, however, little is known about either the intrinsic effects of SB-334867 on the normal structure of feeding behaviour, or its effects upon orexin-A-induced behavioural change. In the present study, we have employed a continuous monitoring technique to characterize the effects of SB-334867 (3-30 mg/kg, i.p.) on the microstructure of rat behaviour during a 1-h test with palatable wet mash. Administered alone, SB-334867 (30 mg/kg, but not lower doses) significantly reduced food intake and most active behaviours (eating, grooming, sniffing, locomotion and rearing), while increasing resting. Although suggestive of a behaviourally nonselective (i.e. sedative) action, the structure of feeding behaviour was well-preserved at this dose level, with the reduction in behavioural output clearly attributable to an earlier onset of behavioural satiety. As previously reported, orexin-A (10 microg per rat i.c.v.) stimulated food intake, increased grooming and delayed the onset of behavioural satiety. Pretreatment with SB-334867 dose-dependently blocked these effects of orexin-A, with significant antagonism evident at dose levels (3-10 mg/kg) below those required to produce intrinsic behavioural effects under present test conditions. Together, these findings strongly support the view that orexin-A is involved in the regulation of feeding patterns and that this influence is mediated through the orexin-1 receptor.

Animals↗
PubMed2001

A novel technique to demonstrate disturbed appetite profiles in haemodialysis patients.

BACKGROUND: Malnutrition is common among dialysis patients and is associated with an adverse outcome. One cause of this is a persistent reduction in nutrient intake, suggesting an abnormality of appetite regulation. METHODS: We used a novel technique to describe the appetite profile in 46 haemodialysis (HD) patients and 40 healthy controls. The Electronic Appetite Rating System (EARS) employs a palmtop computer to collect hourly ratings of motivation to eat and mood. We collected data on hunger, desire to eat, fullness, and tiredness. HD subjects were monitored on the dialysis day and the interdialytic day. Controls were monitored for 1 or 2 days. RESULTS: Temporal profiles of motivation to eat for the controls were similar on both days. Temporal profiles of motivation to eat for the HD group were lower on the dialysis day. Mean HD scores were not significantly different from controls. Dietary records indicated that dialysis patients consumed less food than controls. CONCLUSIONS: Our data indicate that the EARS can be used to monitor subjective appetite states continuously in a group of HD patients. A HD session reduces hunger and desire to eat. Patients feel more tired after dialysis. This does not correlate with their hunger score, but does correlate with their fullness rating. Nutrient intake is reduced, suggesting a resetting of appetite control for the HD group. The EARS may be useful for intervention studies.

Adult↗
PubMed2000

Dose-response effects of orexin-A on food intake and the behavioural satiety sequence in rats.

Although intracerebroventricular (i.c.v.) administration of orexin-A has been reported to stimulate food intake and/or feeding behaviour in rats, mice and goldfish, little attention has thus far been paid to its effects on normal patterns of feeding. In the present study, a continuous monitoring technique was used to characterise the effects of this novel neuropeptide on the microstructure of rat behaviour during a 1-h test with palatable wet mash. Particular attention was devoted to the behavioural satiety sequence, in which feeding is followed by grooming and resting. Although results confirmed the hyperphagic effects of orexin-A (3.33-30.0 microg i.c. v.), gross behavioural analysis failed to reveal any reliable effects of peptide treatment on eating, drinking, sniffing, grooming, resting, locomotion or rearing. However, microstructural analysis revealed behavioural effects of orexin-A that are both dose- and time-dependent. At lower doses (3.33-10.0 microg), orexin-A primarily delayed behavioural satiety, i.e. the normal transition from eating to resting. In contrast, the 30 microg dose initially induced a sedative-like effect, significantly suppressing eating and other active behaviours for the first 15-20 min of the test period. This sedative-like effect resulted in a phase-shifting of the entire behavioural sequence with higher than control levels of eating, grooming, locomotion, rearing and sniffing observed over the second half of the test session. Present findings illustrate the advantages of microstructural behavioural analysis and suggest that the hyperphagic response to low doses of orexin-A results largely from a delay in behavioural satiety while that seen in response to high doses may occur in rebound to initial behavioural suppression. Further studies will be required to confirm the identity of the specific orexin receptors (i.e. OX(1) or OX(2)) involved in mediating the dose-dependent behavioural effects reported.

Animals↗
PubMed2000

Pharmacology of appetite suppression.

Despite a rising worldwide epidemic of obesity there is currently only a very small number of anti-obesity drugs available to manage the problem. Large numbers of differing pharmacological agents reliably produce a reduction in food intake when administered acutely to animals, and when administered chronically they result in a significant decrease in body mass. Behavioural analysis of drug-induced anorexia in animals demonstrates that various compounds profoundly effect feeding behaviour in differing ways. This indicates the variety of mechanisms by which pharmacological agents can induce changes in food intake, body weight and eventually body composition. Some of the same drugs produce decreases in food intake and weight loss in humans. Some of these drugs do so by modifying the functioning of the appetite system as measured by subjective changes in feelings of hunger and fullness (indices of satiety). Such drugs can be considered as "appetite suppressants" with clinical potential as anti-obesity agents. Other drugs induce changes in food intake and body weight through various physiological mechanisms inducing feelings of nausea or even by side effect related malaise. Of the drugs considered suitable candidates for appetite suppressants are agents which act via peripherally satiety peptide systems (such as CCK, Bombesin/GRP, Enterostatin and GLP-1), or alter the CNS levels of various hypothalamic neuropeptides (NPY, Galanin, Orexin and Melanocortins) or levels of the key CNS appetite monoamine neurotransmitters such as serotonin (5-HT) and noradrenaline (NA). Recently, the hormone leptin has been regarded as a hormonal signal linking adipose tissue status with a number of key central nervous system circuits. The peptide itself stimulates leptin receptors and it links with POMC and MC-4 receptors. These receptors may also provide drug targets for the control of appetite. Any changes induced by a potential appetite suppressant should be considered in terms of the (i) psychological experience and behavioural expression of appetite, (ii) metabolism and peripheral physiology, and (iii) functioning of CNS neural pathways. In humans, modulation of appetite may involve changes in total caloric consumption, subjective changes in feelings of hunger and fullness, preferences for specific food items, and general macronutrient preferences. These may be expressed behaviourally as changes in meal patterns, snacking behaviour and food choice. Within the next 20 years it is certain that clinicians will have a new range of anti-obesity compounds available to choose from. Such novel compounds may act on a single component of the appetite system or target a combination of these components detailed in this review. Such compounds used in combination with lifestyle changes and dietary intervention may be useful in dealing with the rising world epidemic of obesity.

Animals↗
PubMed2000

Selective effects of acute exercise and breakfast interventions on mood and motivation to eat.

The effects of exercise and breakfast manipulations on mood and motivation to eat were assessed in 11 healthy females who were regular exercisers and habitual breakfast eaters. The study involved a two by two repeated-measures design, with exercise (or no exercise) and a high-energy breakfast (or low-energy breakfast) as the repeated measures. The exercise or no-exercise session (0800 h) was followed by consumption of the low- or high-energy breakfast (0900 h). An ad libitum lunch test meal was provided 4 hours after the beginning of the exercise session (1200 h). Mood and motivation to eat were continuously tracked from 0800 until 1700 h by an electronic appetite ratings system (EARS). In general, morning subjective mood states (e.g., contentment) were significantly lower in the low-energy breakfast condition, but exercise reversed this effect. Exercise also significantly decreased feelings of lethargy, independent of the breakfast condition. Desire-to-eat and fullness ratings were significantly increased in the low-energy breakfast and high-energy breakfast conditions, respectively. Impairments of mood disappeared in the afternoon after consumption of an ad libitum lunch. In these healthy young adults, the condition inducing the largest energy deficit (exercise and low-energy breakfast) was not associated with the lowest mental states.

Adult↗
PubMed2000

Macronutrients and mental performance.

There is currently intense interest in the effects of macronutrients on psychological states, mental performance, and well-being. A strong theoretical perspective has guided work on carbohydrates and their relation to brain serotoninergic function with concomitant effects on performance. The clearest and most reliable effects have been observed for the beneficial action of glucose on cognitive performance, supported by investigations of hypoglycemia, which is associated with general impairment of cognitive performance. The effects of complex carbohydrates are less distinct and change with time of day; e.g., carbohydrate at breakfast tends to improve morning performance. However, these studies are rarely decisive. Far fewer experiments have been performed on protein and fat, and it is difficult to draw any firm conclusions. Macronutrients are seldom given alone, proportions of protein and fat differ greatly between studies, and comparisons are frequently performed with no food at all. Food intake may mitigate the effects of low doses but not of high doses of alcohol on performance. Effects of macronutrients on cognitive performance may be dependent on their effects on glucose metabolism, metabolic activation, or serotonin. Other factors that modify effects include time of day, circadian rhythms, type of task, habitual diet, and vulnerability of the population.

Alcohol Drinking↗
PubMed2000

Routes to obesity: phenotypes, food choices and activity.

Gain in body weight over a number of years could be achieved through cumulative positive energy balances. These positive balances could come about through adjustments in the various components of energy expenditure or fuel utilization, together with shifts in food selection or eating patterns leading to adjustments in macronutrient intake. This means that many combinations of intake and expenditure could lead to a positive energy balance; these combinations can be called routes to body weight gain. However, these routes are difficult to trace by studying random samples of individuals. Previous investigations have found a clear association between high fat consumption and the occurrence of obesity, and although a high fat intake is a strong behavioural risk factor for weight gain, the relationship does not constitute a biological inevitability. Some normal-weight and lean individuals appear to eat a high-fat diet. To investigate reasons for this we have studied individuals initially defined by particular clusters of dietary characteristics related to fat and carbohydrate consumption. Habitual high-fat (HF) and low-fat (LF) consumers have been termed phenotypes. Various aspects of energy expenditure (physiological and behavioural) and energy intake were measured in these individuals with contrasting profiles. HF phenotypes had high intakes of fatty foods and an overall higher energy intake than LF. However, these groups of young adult males had similar BMIs and percentage body fat. The HF had a significantly higher resting metabolic rate (RMR) and a lower RQ, together with high plasma fasting leptin levels, and a higher sleeping heart rate. In HF individuals the physical activity level was somewhat lower and they had significantly more periods of sedentary behaviour than LF subjects. Although HF individuals appear to be more vulnerable to developing obesity, both phenotypes carry particular risk factors and protective factors for weight gain. The use of phenotypes has allowed the identification of different potential routes to weight gain. Different strategies are required to prevent age-related increase in body weight in these quite different individuals.

Diet↗
PubMed2000

The use of visual analogue scales to assess motivation to eat in human subjects: a review of their reliability and validity with an evaluation of new hand-held computerized systems for temporal tracking of appetite ratings.

This present paper reviews the reliability and validity of visual analogue scales (VAS) in terms of (1) their ability to predict feeding behaviour, (2) their sensitivity to experimental manipulations, and (3) their reproducibility. VAS correlate with, but do not reliably predict, energy intake to the extent that they could be used as a proxy of energy intake. They do predict meal initiation in subjects eating their normal diets in their normal environment. Under laboratory conditions, subjectively rated motivation to eat using VAS is sensitive to experimental manipulations and has been found to be reproducible in relation to those experimental regimens. Other work has found them not to be reproducible in relation to repeated protocols. On balance, it would appear, in as much as it is possible to quantify, that VAS exhibit a good degree of within-subject reliability and validity in that they predict with reasonable certainty, meal initiation and amount eaten, and are sensitive to experimental manipulations. This reliability and validity appears more pronounced under the controlled (but more artificial) conditions of the laboratory where the signal:noise ratio in experiments appears to be elevated relative to real life. It appears that VAS are best used in within-subject, repeated-measures designs where the effect of different treatments can be compared under similar circumstances. They are best used in conjunction with other measures (e.g. feeding behaviour, changes in plasma metabolites) rather than as proxies for these variables. New hand-held electronic appetite rating systems (EARS) have been developed to increase reliability of data capture and decrease investigator workload. Recent studies have compared these with traditional pen and paper (P&P) VAS. The EARS have been found to be sensitive to experimental manipulations and reproducible relative to P&P. However, subjects appear to exhibit a significantly more constrained use of the scale when using the EARS relative to the P&P. For this reason it is recommended that the two techniques are not used interchangeably.

Appetite↗
PubMed2000

Reproducibility, power and validity of visual analogue scales in assessment of appetite sensations in single test meal studies.

OBJECTIVE: To examine reproducibility and validity of visual analogue scales (VAS) for measurement of appetite sensations, with and without a diet standardization prior to the test days. DESIGN: On two different test days the subjects recorded their appetite sensations before breakfast and every 30 min during the 4.5 h postprandial period under exactly the same conditions. SUBJECTS: 55 healthy men (age 25.6+/-0.6 y, BMI 22.6+/-0.3 kg¿m2). MEASUREMENTS: VAS were used to record hunger, satiety, fullness, prospective food consumption, desire to eat something fatty, salty, sweet or savoury, and palatability of the meals. Subsequently an ad libitum lunch was served and energy intake was recorded. Reproducibility was assessed by the coefficient of repeatability (CR) of fasting, mean 4.5 h and peak/nadir values. RESULTS: CRs (range 20-61 mm) were larger for fasting and peak/nadir values compared with mean 4.5 h values. No parameter seemed to be improved by diet standardization. Using a paired design and a study power of 0.8, a difference of 10 mm on fasting and 5 mm on mean 4.5 h ratings can be detected with 18 subjects. When using desires to eat specific types of food or an unpaired design, more subjects are needed due to considerable variation. The best correlations of validity were found between 4.5 h mean VAS of the appetite parameters and subsequent energy intake (r=+/-0.50-0.53, P<0.001). CONCLUSION: VAS scores are reliable for appetite research and do not seem to be influenced by prior diet standardization. However, consideration should be given to the specific parameters being measured, their sensitivity and study power. International Journal of Obesity (2000)24, 38-48

Adult↗
PubMed2000

Lean male high- and low-fat phenotypes--different routes for achieving energy balance.

OBJECTIVE: This study investigated how energy expenditure may contribute to energy balance in lean male individuals consuming a diet either high or low in fat. METHODS: Fifteen high-fat phenotypes (HF) and 15 low-fat phenotypes (LF) participated in the study. Energy intake and macronutrient intake variables were assessed using a food frequency questionnaire and 3 day food diaries. Total energy expenditure (TEE) was estimated from 24h heart rate monitoring and factorial methods. Habitual physical activity was measured using the Baecke questionnaire. RESULTS: There were no anthropometric differences between HF and LF. HF had a significantly higher heart rate over 24 h; this was particularly evident during the sleeping phase. There were no differences in TEE between HF and LF, but HF were more sedentary than LF. CONCLUSIONS: In these young male subjects a high fat intake was associated with increased sedentariness; however, higher heart rates (basal and post-meal) could indicate that energy balance was achieved by relatively high basal metabolism and an increase in dietary-induced themogenesis (physiological route). In contrast LF could maintain energy balance through relatively high levels of physical activity (behavioural route).

Adolescent↗