Biomedical subjects

S Whybrow

Publications and source records attributed to S Whybrow.

7 recordsLinked to original sources

PubMed2006

The evaluation of an electronic visual analogue scale system for appetite and mood.

Our objective was to evaluate a new electronic visual analogue scale (VAS) system for logging subjective motivation to eat ratings. In total, 10 men and 10 women completed both electronic and traditional pen and paper versions of the questionnaire every hour of the waking day. Subjects consumed a standard medium-fat diet, which was fixed at 1.6.BMR. Correlation coefficients for scores obtained by both methods were significant for all questions, with R(2) values ranging from 67 to 87%. However, Bland and Altman plots and paired t-tests identified significant bias between the two methods for five of the nine individual questions. These were questions that tended to be scored more towards the ends of the VAS. The new electronic VAS produces comparable, but not interchangeable, results to the traditional pen and paper method in the study of appetite and mood, while offering advantages of improved reliability in data collection.

Adult↗

PubMed2005

Resistance and susceptibility to weight gain: individual variability in response to a high-fat diet.

An obesigenic environment is a potent force for promoting weight gain. However, not all people exposed to such an environment become obese; some remain lean. This means that some people are susceptible to weight gain (in a weight-promoting environment) and others are resistant. Identifying the characteristics of appetite control and food motivation in these two groups could throw light on the causes of weight gain and how this can be either treated or prevented. We have investigated the issue experimentally by identifying people who habitually consume a high-fat diet (greater than 43% fat energy). These individuals have been termed high-fat phenotypes. We have compared individuals, of the same age (mean=37 years old) and gender (male), who have gained weight (BMI=34) or who have remained lean (BMI=22). The susceptible individuals are characterised by a cluster of characteristics including a weak satiety response to fatty meals, a maintained preference for high-fat over low-energy foods in the post-ingestive satiety period, a strong hedonic attraction to palatable foods and to eating, and high scores on the TFEQ factors of Disinhibition and Hunger. The analysis of large databases suggests that this profile of factors contributes to an average daily positive energy balance from food of approximately 0.5 MJ. This profile of characteristics helps to define the symptomatology of a thrifty phenotype.

Appetite↗

PubMed2004

Energy density, diet composition and palatability: influences on overall food energy intake in humans.

This paper considers the role of energy density (ED), diet composition and palatability in the control of energy intake (EI) in humans through several related considerations: (i) the relationship between ED and diet composition, (ii) the relationship between ED, diet composition and EI, (iii) the relationship between palatability and EI, (iv) the relationship between ED, palatability and EI, (v) the importance of postingestive factors in influencing palatability in the longer term, (vi) the contribution of sensory and nutritional factors to dietary hyperphagia and (vii) the implications these considerations have for people living their normal lives in their natural environment. The main factors influencing ED are the fat and water content of foods. Energy density does elevate EI, especially in short-term studies where it can account for >40% of the variance in EI. In real life, ED accounts for only approximately 7% of the variance in EI. This is because the determinants of EI are multifactorial and also because the short-term effects of ED on EI do not translate into the longer term. We argue that part of the longer term amelioration of short-term effects of ED on EI is due to learned compensation, based on the postingestive consequences of consuming familiar food that differ in ED. More energy-dense foods tend to be more palatable but we learn to consume them in smaller portion sizes. In the longer term, the perceived palatability of a food is strongly influenced by the postingestive consequences of eating it. This effect can override sensory factors alone. This implies that nutrient mimetics, if used continuously, would not be as efficacious as initially supposed and that their ad hoc use may undermine the stability of learned appetites and satieties for foods with different EDs and contribute to the poor weight control capability exhibited by consumers at large.

Diet↗

PubMed2004

Rate and extent of compensatory changes in energy intake and expenditure in response to altered exercise and diet composition in humans.

We assessed the effect of no exercise (Nex; control) and high exercise level (Hex; approximately 4 MJ/day) and two dietary manipulations [a high-fat diet (HF; 50% of energy, 700 kJ/100 g) and low-fat diet (LF; 20% of energy, 300 kJ/100 g)] on compensatory changes in energy intake (EI) and energy expenditure (EE) over 7-day periods. Eight lean men were each studied four times in a 2 x 2 randomized design. EI was directly quantified by weight of food consumed. EE was assessed by heart rate (HR) monitoring. Body weight was measured daily. Mean daily EE was 17.6 and 11.5 MJ/day (P < 0.001) on the pooled Hex and Nex treatments, respectively. EI was higher on HF diets (13.4 MJ/day pooled) compared with the LF diets (9.0 MJ/day). Regression analysis showed that these energy imbalances induced significant compensatory changes in EB over time of approximately 0.3-0.4 MJ/day (P < 0.05). These were due to changes in both EI and EE in the opposite direction to the perturbation in energy balance. These changes were significant, small but persistent, amounting to approximately 0.2 and approximately 0.35 MJ/day for EI and EE, respectively.

Adaptation, Physiological↗

PubMed2003

Cross talk between physical activity and appetite control: does physical activity stimulate appetite?

Physical activity has the potential to modulate appetite control by improving the sensitivity of the physiological satiety signalling system, by adjusting macronutrient preferences or food choices and by altering the hedonic response to food. There is evidence for all these actions. Concerning the impact of physical activity on energy balance, there exists a belief that physical activity drives up hunger and increases food intake, thereby rendering it futile as a method of weight control. There is, however, no evidence for such an immediate or automatic effect. Short (1-2 d)-term and medium (7-16 d)-term studies demonstrate that men and women can tolerate substantial negative energy balances of < or = 4 MJ energy cost/d when performing physical activity programmes. Consequently, the immediate effect of taking up exercise is weight loss (although this outcome is sometimes difficult to assess due to changes in body composition or fluid compartmentalization). However, subsequently food intake begins to increase in order to provide compensation for about 30% of the energy expended in activity. This compensation (up to 16 d) is partial and incomplete. Moreover, subjects separate into compensators and non-compensators. The exact nature of these differences in compensation and whether it is actually reflective of non-compliance with protocols is yet to be determined. Some subjects (men and women) performing activity with a cost of < or = 4 MJ/d for 14 d, show no change in daily energy intake. Conversely, it can be demonstrated that when active individuals are forced into a sedentary routine food intake does not decrease to a lower level to match the reduced energy expenditure. Consequently, this situation creates a substantial positive energy balance accompanied by weight gain. The next stage is to further characterize the compensators and non-compensators, and to identify the mechanisms (physiological or behavioural) that are responsible for the rate of compensation and its limits.

Anorexia↗

PubMed2001

Carbohydrates, appetite and feeding behavior in humans.

The view of carbohydrates in relation to obesity has changed over the past few decades from being conducive to overconsumption and weight gain to being protective. This article reviews the mechanisms by which carbohydrate is purported to protect against weight gain. Although carbohydrate is metabolized and stored in the body less efficiently than fat, when de novo lipogenesis is invoked on very high carbohydrate diets, the beneficial effect on energy balance is likely to be minimal when typical high fat Western diets are consumed. However, it has been suggested that high carbohydrate foods may influence energy balance by reducing food intake through greater satiety effects, reducing energy density and displacing fat from the diet-the fat-sugar seesaw effect. To date, there seem to be few differences between sugars and starches on satiety and energy intake, but few studies have examined this. Some reduced-fat, and, therefore, higher carbohydrate, foods are highly energy dense. High carbohydrate foods do not necessarily have a low energy density. Evidence from recent studies suggests that adding carbohydrate, and especially sugar, to the diet neither displaces fat from the diet nor protects against elevated energy intake. Although it is easier to overeat on high fat than low fat foods, simply replacing fat with carbohydrate in the diet may not be as protective against overconsumption as the energy density or fat-sugar seesaw arguments suggest.

Appetite↗

PubMed2000

Altering the temporal distribution of energy intake with isoenergetically dense foods given as snacks does not affect total daily energy intake in normal-weight men.

The objectives of the present study were to examine the effects of (1) ingesting mandatory snacks v. no snacks and (2) the composition of isoenergetically-dense snacks high in protein, fat or carbohydrate, on food intake and energy intake (EI) in eight men with ad libitum access to a diet of fixed composition. Subjects were each studied four times in a 9 d protocol per treatment. On days 1-2, subjects were given a medium-fat maintenance diet estimated at 1.6 x resting metabolic rate (RMR). On days 3-9, subjects consumed three mandatory isoenergetic, isoenergetically dense (380 kJ/100 g) snacks at fixed time intervals (11.30, 15.30 and 19.30 hours). Total snack intake comprised 30% of the subjects' estimated daily energy requirements. The treatments were high protein (HP), high carbohydrate (HC), high fat (HF) and no snack (NS). The order was randomized across subjects in a counterbalanced, Latin-square design. During the remainder of the day, subjects had ad libitum (meal size and frequency) access to a covertly manipulated medium-fat diet of fixed composition (fat:carbohydrate:protein, 40:47:13 by energy), energy density 550 kJ/100 g. All foods eaten were investigator-weighed before ingestion and left-overs were weighed after ingestion. Subjective hunger and satiety feelings were tracked hourly during waking hours using visual analogue scales. Ad libitum EI amounted to 13.9 MJ/d on the NS treatment compared with 11.7, 11.7 and 12.2 MJ/d on the HP, HC and HF diets respectively (F(3,21) 5.35; P = 0.007, SED 0.66). Total EI values were not significantly different at 14.6, 14.5, 15.0 and 14.2 MJ/d respectively. Snack composition did not differentially affect total daily food intake or EI. Average daily hunger was unaffected by the composition of the snacks. Only at 12.00 hours did subjects feel significantly more hungry during the NS condition, relative to the other dietary treatments (F(3,18) 4.42; P = 0.017). Body weight was unaffected by dietary treatment. In conclusion, snacking per se led to compensatory adjustments in feeding behaviour in lean men. Snack composition (with energy density controlled) did not affect the amount eaten of a diet of fixed composition. Results may differ in real life where subjects can alter both composition and amount of food they eat and energy density is not controlled.

Adult↗