Changes in hunger and fullness in relation to gut peptides ...

Summary

Background & aims

Alternate day fasting (ADF; 25% energy intake “fast day”, alternated with an ad libitum intake “feed day”) is effective for weight loss. Whether or not ADF modulates hunger, fullness and gut peptides in a way that enhances dietary compliance and weight loss, remains unknown. Accordingly, this study examined the effect of ADF on postprandial appetite ratings and gut peptides.

Methods

Obese subjects (n = 59) participated in an 8-week ADF protocol where food was provided on the fast day.

Results

Body weight decreased (P < 0.0001) by 3.9 ± 0.6 kg after 8 weeks of diet. Reductions (P < 0.05) in fat mass (−2.2 ± 0.2 kg), fat free mass (−1.4 ± 0.2 kg), visceral fat mass (−0.1 ± 0.1 kg), and resting metabolic rate (RMR; −104 ± 28 kcal/day) were also observed. Fasting leptin and insulin decreased (P < 0.05), while AUC ghrelin levels increased (P < 0.05). Despite these metabolic changes, there was no increase in subjective hunger by the end of the study. Furthermore, fullness and PYY increased (P < 0.05). Fat free mass and RMR were not related to hunger or ghrelin at any time point.

Conclusion

These findings suggest that the absence of a compensatory increase in hunger in conjunction with an increase in sensations of fullness may contribute to the weight loss efficacy of an 8-week ADF regimen.

Introduction

Alternate day fasting (ADF) is a novel weight loss approach that has gained recent popularity [1]. ADF consists of a 25% energy intake “fast day” alternated with an ad libitum intake “feed day”. Recent studies show that obese adults lose 4–8% of body weight after 8–12 weeks [2], [3], [4], [5], [6], [7], and that adherence to ADF remains high (90–95%) throughout the duration of the trial [8]. Difficulty in managing sensations of hunger is one of the main reasons given for aborted or unsuccessful attempts to diet [9], [10]. The precise reason why compliance remains elevated with ADF is not clear, but may be related to favorable changes in hunger and fullness [11]. For instance, in a trial by Klempel et al. [8] hunger decreased on the fast day after 8 weeks of ADF. Complementary to these findings, Bhutani et al. [12] observed reductions in hunger and increases in fullness on the fast day after 12 weeks of ADF. It should be noted, however, that these findings are limited in that subjective ratings of hunger and fullness were only measured at one time point on the evening of a fast day (pre and post treatment), and that post-prandial levels before and after ADF were not assessed [8], [12]. Moreover, none of these studies [8], [12] employed objective hormonal measures of appetite, such as ghrelin (indicator of hunger) or PYY and glucagon like peptide-1 (indicators of fullness). Thus, whether or not these findings for hunger and fullness can be reproduced when more robust measures are employed, warrants investigation.

Also of interest, is the role of fat free mass and resting metabolic rate (RMR) in mediating these decreases in hunger. Previous findings suggest that fat free mass and RMR generally decrease in response to weight loss [13], [14], and that reductions in these parameters are related to lower hunger levels [15]. Although the data for ADF are limited, evidence suggests that fat free mass and RMR typically decrease with 4–8% weight loss [5], [6], [7], [16], while some studies show no change [2], [3], [4]. Whether or not reductions in fat free mass and RMR are associated with decreases in hunger during ADF is an important question that has yet to be addressed.

Accordingly, this study examined the effect of 8-weeks of ADF on fasting and postprandial appetite ratings and gut peptide concentrations in obese adults. The degree to which changes in fat free mass and RMR correlate with changes in hunger and gut hormone concentrations, was also assessed.

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Section snippets

Subjects

Participants were recruited from the Chicago area by flyers. Subjects were obese (BMI between 30 and 39.9 kg/m2), 25–65 years of age, pre-menopausal or post-menopausal, physical activity level at <3 h/week at 2.5 to 4.0 metabolic equivalents (METs) for 3 months prior to the study, weight stable for 3 months prior to the study (<4 kg weight loss or gain), non-diabetic, no history of cardiovascular disease, non-smokers, and not taking any medications that would affect study outcomes. A total of

Baseline characteristics and dropouts

Of the 74 subjects who commenced the study, 59 completed the entire protocol. Dropouts were primarily due to scheduling conflicts (n = 2), personal reasons (n = 4), issues with the ADF diet (n = 6, i.e. dislike of foods provided on the fast day), and unspecified reasons (n = 3). Subjects (50 females/9 males) who completed the study were middle age (46 ± 1 y), obese (93.6 ± 2.2 kg; BMI 34 ± 1 kg/m2), and not physically active.

Dietary adherence, body weight, body composition, and RMR

As reported previously [16], subjects met their energy goal on 91± 2%

Discussion

This is the first study to examine the impact of ADF on appetite ratings and gut peptide concentrations in response to a test meal. We show here that despite significant reductions in body weight (fat and fat free mass), leptin and insulin, and an increase in AUC ghrelin, post-prandial hunger levels did not change when baseline was compared to post-treatment after 8 weeks of ADF. Furthermore, AUC fullness and PYY levels increased from baseline to post-treatment, while GLP-1 levels remained

Funding source

Kinesiology and Nutrition, University of Illinois, Chicago.

Conflict of interest

Krista Varady is the author of the book “The Every Other Day Diet” published by the Hachette Book Group. The other authors have no competing interests to disclose.

Acknowledgments

KKH designed the experiment, ran the clinical trial, analyzed the data, and wrote the manuscript. CMK, JFT, AB, SB and KG assisted with the conduction of the clinical trial and performed the laboratory analyses. CG and GF helped with the data analysis and the preparation of the manuscript. KAV assisted with the design of the experiment, data analyses and the preparation of the manuscript.

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