Compliance of participants undergoing a ‘5-2’ intermittent fasting diet and impact on body weight

Cook Florence, Jasmin Langdon-Daly, Serpell Lucy

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Intermittent fasting (IF) has grown in popularity as a weight loss tool, where caloric intake is fully/partially restricted on a recurring basis. This study aimed to assess compliance with IF fast-day calorie restriction and whether 5-2 IF leads to reduced overall energy intake, weight loss and compensatory increased energy intake on non-fast days.

Participants completed diet diaries at baseline and 28 days post 5-2 IF in a repeated measures within-subjects design. 5-2 IF required restricted energy intake to 500 kcal/day (women), 650 kcal/day (men) on two ‘fast’ days/week whilst eating ad-libitum on other days.

52 participants were included (n = 42 female; age 44 ± 11.2yrs). Median weight loss after 28 days 5–2 IF was statistically significant (1.8 [-2 - 7.3 IQR = 2.2]kg; 2.8 [-2.7–11.2 IQR = 2.5]% p < 0.001). There was a significant reduction in total energy intake during 5–2 IF compared with pre-diet (median 1288.0 [IQR 423.8]kcal and median 1751.5 [IQR 505.3]kcal respectively, p < 0.001). Carbohydrate, protein and fat consumption proportionately reduced during 5–2 IF. Participants had significantly higher energy intake (p < 0.001) on non-fast days that followed a fast day (1928.4 ± 711.9 kcal) compared to non-fast days not following a fast day (1316.2 ± 310.0 kcal). 55.8% complied with fast day calorie restrictions.

5-2 IF was associated with significantly reduced energy intake, and weight loss over a 28-day period. Compliance rate was lower than most previous studies. Participants had significantly higher energy intake on non-fast days following fast days suggesting fasting may lead to over-compensation. Further research should investigate strategies to improve compliance and long-term sustainability of IF diets.
Original languageEnglish
JournalClinical Nutrition ESPEN
Early online date17 Aug 2022
Publication statusPublished - 10 Dec 2022

Bibliographical note

Conflicts of interest and funding statement
The authors declare no conflicts of interest. This project did not
receive any specific grant from funding agencies in the public,
commercial, or not-for-profit sectors


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