Research reportReproducibility of subjective appetite ratings and ad libitum test meal energy intake in overweight and obese males☆
Introduction
Appetite and energy intake (EI) are often measured in the laboratory using visual analogue scales (VAS) and ad libitum test meals respectively. To assess whether these methods are sensitive to detect changes in appetite and EI, it is important to determine their reproducibility. The reproducibility of subjective appetite ratings (Arvaniti et al, 2000, Barkeling et al, 1995, Flint et al, 2000, Gonzalez et al, 2012, Raben et al, 1995, Stratton et al, 1998) and ad libitum EI (Arvaniti et al, 2000, Gregersen et al, 2008, Nair et al, 2009) has been studied in normal weight adults. Overall, it appears that while the reproducibility will vary depending on the parameter reported, VAS demonstrates a good degree of intra-individual reproducibility (see Stubbs et al., 2000 for a comprehensive review). Similarly, EI at an ad libitum meal has been shown to be reproducible in normal weight males (Flint et al., 2007). Surprisingly, despite being frequently assessed in response to interventions in overweight and obese individuals, little information exists on the reproducibility of these measures in this population.
Given some evidence that gut peptide (Valera Mora et al., 2005) and appetite (Barkeling et al., 1995) responses may vary according to body composition, it is possible that the reproducibility of appetite and EI will be different in overweight and obese individuals. For example, a range of factors such as the reward value of food, social desirability, eating behaviour characteristics (e.g. disinhibition) and even exercise (King, 1999) may be more likely to influence appetite ratings and EI in overweight and obese individuals (Barkeling et al, 2007, Barkeling et al, 1995). Barkeling et al. (1995) compared VAS ratings in normal weight and obese individuals and demonstrated that while hunger sensations were more reproducible in obese men, desire to eat sensations were less reproducible. However, in this study, VAS ratings were only measured immediately before and after the test meal. In the majority of studies, VAS are generally completed before, immediately after a test meal and then periodically at regular intervals (varying from 15 to 30 min up to hourly) usually for 3–5 h, or until the start of the next meal (Blundell et al., 2010). To the best of our knowledge the reproducibility of postprandial (3–5 h) appetite ratings between two separate days has not been previously documented in overweight and obese individuals.
With regard to ad libitum EI, EI at lunch was previously reported to be highly reproducible in eight overweight/obese individuals using the preload paradigm (Lara, Taylor, & Macdonald, 2010). However, the ad libitum lunch meal was provided at a relatively short interval (90 min) after the preload in this study (Lara et al., 2010). The reproducibility could be influenced by the time interval (Rolls et al., 1991). Therefore, there is a need for further understanding of the reproducibility of subjective appetite ratings and ad libitum EI in overweight and obese individuals under standardised conditions. This knowledge can be used to inform appropriate sample sizes for the design of studies investigating changes in these parameters in the pathogenesis or treatment of obesity.
The aims of the present study were to (i) determine the reproducibility of VAS for appetite ratings and ad libitum EI following a more typical inter-meal interval, (ii) calculate minimum sample sizes required to detect hypothetical changes in appetite ratings and ad libitum EI in prospective studies, and (iii) examine relationships amongst the various appetite measures, in overweight and obese males.
Section snippets
Subjects
Fifteen overweight and obese men [BMI 30.3 ± 4.9 kg/m2, percent body fat 32.1 ± 8.0%, age 34.9 ± 10.6 years] participated. Nine were classified as overweight and six obese by BMI. Eating behaviour was assessed using the Three Factor Eating Questionnaire (Stunkard & Messick, 1985). Height was measured without shoes to the nearest 0.5 cm and weight to the nearest 0.01 kg. Body composition was measured using air displacement plethysmography (Bodpod, Concord, CA). None of the participants had a
Results
All participants (n = 15) completed all components of the study. TFEQ scores for dietary Restraint, Hunger and Disinhibition were 7 ± 3, 6 ± 3, and 8 ± 3 respectively.
Discussion
Food intake methodology is becoming increasingly important in obesity research (Blundell et al., 2009). It follows that claims about changes in appetite or the effects of interventions in overweight or obese people should be based on evidence from studies on this population (Blundell et al., 2010). The present study assists to inform the design and interpretation of studies by providing novel information regarding the reproducibility of subjective appetite ratings and ad libitum test meal EI in
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Acknowledgements: We are particularly grateful to the participants in this study. This study was supported by a Queensland University of Technology Postgraduate Research Award (QUTPRA). Conflict of interest: The authors declare no conflicts of interest. Authorship: The authors' responsibilities were as follows – KMH, NMB and NAK contributed to the design of the study; KMH collected the data, analysed the data and drafted the manuscript; NMB and NAK contributed to data analysis and critical revision of the manuscript. All authors read and approved the final manuscript.