Alexandra M. Johnstone

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.

Polymorphisms of the FTO gene are associated with variation in energy intake, but not energy expenditure.

The FTO gene has significant polymorphic variation associated with obesity, but its function is unknown. We screened a population of 150 whites (103F/47M) resident in NE Scotland, United Kingdom, for variants of the FTO gene and linked these to phenotypic variation in their energy expenditure (basal metabolic rate (BMR) and maximal oxygen consumption VO2max) and energy intake. There was no significant association between the FTO genotype and BMR or VO2max. The FTO genotype was significantly associated (P = 0.024) with variation in energy intake, with average daily intake being 9.0 MJ for the wild‐type TT genotype and 10.2 and 9.5 MJ for the “at risk” AT and AA genotypes, respectively. Adjusting intake for BMR did not remove the significance (P = 0.043). FTO genotype probably affects obesity via effects on food intake rather than energy expenditure.

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; ∼1.9 MJ/day) and high exercise level (Hex; ∼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 (∼33% of EE due to exercise). Accurate adjustments of El to acute increases in EE are likely to take weeks rather than days.

The effect of an incremental increase in exercise on appetite, eating behaviour and energy balance in lean men and women feeding ad libitum

The effects of incremental exercise on appetite, energy intake (EI), expenditure (EE) and balance (EB) in lean men and women were examined. Six men (age 29.7 (SD 5.9) years, weight 75.2 (SD 15.3) kg, height 1.75 (SD 0.11) m) and six women (age 24.7 (SD 5.9) years, weight 66.7 (SD 9.10) kg, height 1.70 (SD 0.09) m) were each studied three times during a 16 d protocol, corresponding to no additional exercise (Nex), moderate-intensity exercise (Mex; 1.5-2.0 MJ/d) and high-intensity exercise (Hex; 3.0-4.0 MJ/d) regimens. Subjects were fed to EB during days 1-2, and during days 3-16 they fed ad libitum from a medium-fat diet of constant composition. Daily EE, assessed using the doubly labelled water method, was 9.2, 11.6 and 13.7 MJ/d (P < 0.001; SED 0.45) for the women and 12.2, 14.0 and 16.7 MJ/d (P = 0.007; SED 1.11) for the men on the Nex, Mex and Hex treatments, respectively. EI was 8.3, 8.6 and 9.9 MJ/d (P = 0.118; SED 0.72) for the women and 10.6, 11.6 and 12.0 MJ/d (P = 0.031; SED 0.47) for the men, respectively. On average, subjects compensated for about 30 % of the exercise-induced energy deficit. However, the degree of compensation varied considerably among individuals. The present study captured the initial compensation in EI for exercise-induced energy deficits. Total compensation would take a matter of weeks.

Effect of altering the variety of sensorially distinct foods, of the same macronutrient content, on food intake and body weight in men.

Objective: To examine the effect of increasing the variety of sensorially distinct but nutritionally identical foods on appetite, food intake and body weight, over 7 days, in men.Design: Six younger, lean men (mean (s.d.) age 27.0 (2.9) y; weight 74.7 (3.9) kg; height 1.78 (0.03) m; body mass index (BMI) 23.6 (1.1) kg/m2) and six older, overweight men (mean (s.d.) age 39.7 (2.9) y; weight 89.2 (4.4) kg; height 1.78 (0.04) m; BMI 28.1 (0.5) kg/m2) were each studied three times during a 9 day protocol, whilst resident in the Human Nutrition Unit. On days 1–2, subjects consumed a medium fat (MF) maintenance diet (40% fat, 13% protein and 47% carbohydrate by energy) calculated at 1.6× resting metabolic rate (RMR). On days 3–9 subjects had ad libitum access to MF foods (550 kJ/100 g) with every item the same macronutrient composition and energy density. Subjects had continuous ad libitum access to 5, 10 or 15 food items per day on the low-variety (LV), medium-variety (MV) and high-variety (HV) treatments, respectively. The order of treatments was randomized across subjects. Subjective hunger was tracked hourly during waking hours using visual analogue scales (VAS). Body weight (as a proxy of changes in energy balance) was measured before eating and after voiding, each morning.Results: Food and energy intake of the 12 men increased as the variety of foods increased, giving mean energy intakes of 10.13, 11.00 and 11.89 MJ/day on the LV, MV and HV treatments, respectively (F(2,20)=10.32; P<0.001). This effect was ascribable almost entirely to the lean men. Energy intake amounted to 1.57, 1.76 and 1.97×RMR in the lean men and 1.33, 1.40 and 1.45×RMR, for the overweight men on the LV, MV and HV diets, respectively. Weight changes amounted to −0.16, −0.28 and +0.43 kg (lean) −1.03 and −1.52 kg and −0.66 kg (overweight), on the LV, MV and HV diets, respectively. The overweight men may have constrained their energy intake relative to expected requirements. This may have been due to a congnitive effect or an age effect. There was no significant group or diet effect on subjectively rated hunger.Conclusions: These data suggest that increasing the variety of sensorially distinct foods that are virtually identical in composition can increase food and energy intake and in the short to medium term can alter energy balance.Sponsorship: This work was supported by the Scottish Office.European Journal of Clinical Nutrition (2001) 55, 19–28

Plasma concentrations of alpha-MSH, AgRP and leptin in lean and obese men and their relationship to differing states of energy balance perturbation

objective  A great deal of attention has focused on the central role of alpha melanocyte‐stimulating hormone (α‐MSH) and its antagonism at the melanocortin‐4 receptor (MC4R) by agouti related protein (AgRP) in the regulation of energy balance. However, very little is known regarding the function of circulating AgRP and α‐MSH in humans. We aimed to determine whether circulating α‐MSH and AgRP are responsive to long‐term perturbations in energy balance, in a manner consistent with their central putative functions.

Description and evaluation of an experimental model to examine changes in selection between high-protein, high-carbohydrate and high-fat foods in humans.

Objective: To develop and test an experimental model designed to detect changes in selection between foods individually enriched in protein, carbohydrate and fat in human subjects.Design: Randomised counterbalanced (Latin square) design.Setting: The metabolic suite at the Rowett Research Institute’s Human Nutrition Unit.Subjects: 16 normal-weight men (mean BMI=23.5).Interventions: Subjects were each studied 4 times in a 2-day protocol. On day 1 subjects received a fixed maintenance diet; on day 2 they received a mandatory intake as breakfast (08.30) plus a drink at 10.30. This comprised 80% of resting energy requirements as high-protein (HP), high-carbohydrate (HC) or high-fat (HF) foods (60% of energy in each case) or an equal mixture (M) of macronutrients, 33% by energy. All mandatory treatments contained the same energy content and density. From 12.30 onwards, subjects had ad libitum access to a counter-balanced selection of three groups of familiar foods (10 HP, 10 HC and 10 HF; 30 foods in total). Most energy in each food was derived from one macronutrient (∼60%), the remainder being equally split between the other two macronutrients.Results: Subjects were significantly less hungry before lunch on the HP and M (33% protein) treatments (F3,44=7.35; P<0.001). At lunch, they ate more energy after the HF treatment than after any of the other treatment (F1,38=9.00; P=0.005). This was largely in the form of fat and protein, and to a lesser extent carbohydrate. Subsequent energy intake (EI) were lower on the HF treatment, largely through selection of less fat in the afternoon (F1,42=6.90; P=0.012). Daily EIs were similar across treatments.Conclusion: This design appears sensitive meal-to-meal to changes in both nutrient and EIs.Sponsorship: This work was supported by the Scottish Office, Agriculture, Environment and Fisheries Department.

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 Altmans 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.

Effect of an acute fast on energy compensation and feeding behaviour in lean men and women.

AIM: Humans appear to defend against energy deficit to a greater extent than energy surplus. Severe dietary energy restriction resulting in 5–30% weight loss often leads to hyperphagia and weight regain in lean subjects. However, the period of time over which fasting is often endured in Western society are far shorter, ∼1–2 days. This study examined how a 36 h fast effected the subsequent days energy and nutrient intake in a group of 24 healthy, lean men and women.METHOD: Subjects underwent two 2 day treatments, termed ‘fast’ and ‘maintenance’. During the ‘fast’ treatment, subjects were fed a maintenance diet on the day prior to the fast (day −1) to prevent overeating. They then consumed non-energy drinks only, from 20:00 h on day −1 to 08:00 h on day 2 (ad libitum feeding day), thus fasting for 36 h. On the ‘maintenance’ protocol, subjects received a maintenance diet throughout day 1. Throughout day 2 they had ad libitum access to a range of familiar foods, which were the same for both treatments. Body weight, blood glucose and respiratory quotient were used as compliance checks. Hunger was monitored on days −1, 1 and 2 for the fast treatment only.RESULTS: On day 2, average energy intake was 10.2 vs 12.2 MJ/day (s.e.d. 1.0) on the post-maintenance and post-fast periods, respectively (P=0.049). Subjects altered feeding behaviour, in response to the fast, only at breakfast time, selecting a higher-fat meal (P<0.005). Compared to day −1, motivation to eat was elevated during the fast (P<0.05). This continued until breakfast was consumed during the re-feeding period (day 2), when values then returned to baseline.CONCLUSION: These data suggest that a 36 h fast, which generated a negative energy balance of ∼12 MJ, did not induce a powerful, unconditioned stimulus to compensate on the subsequent day.

Assessment of body image in obesity using a digital morphing technique

BACKGROUND Historically, body image research has relied on generic, whole body outlines, which may not be suited to obese individuals. The development of computer generated, individualized digital images to represent body image may be more effective. METHODS Sixty volunteers participated, with three categories of subject: lean, obese and lean regular exercisers. Body image was assessed using a digital morphing technique in comparison to two standard paper questionnaires. RESULTS Using the novel digital morphing tool, obese subjects displayed poorer body awareness (perception) than their lean counterparts (P = 0.03), significantly over-estimating their actual body size. Both genders overestimated body size to a similar degree. For body satisfaction, females wished to be smaller and males to be larger, identifying gender-specific body regions (P < 0.001). Obese subjects showed greatest dissatisfaction (P < 0.001) with body image. There was significant correlation for body image dissatisfaction (P < 0.05) between the digital technique and the questionnaires, which was highest for the figural stimuli questionnaire (r = 0.80, P < 0.001). CONCLUSIONS This method represents a novel and alternative approach to rating body image perception (IP) and satisfaction in obese subjects, particularly providing data on specific regional areas. Body image dissatisfaction appears to be both due to poor body IP compounded with the desire to be smaller.