Weight loss maintenance one year after modified intermittent fasting in circadian-disrupted night shift workers: longer-term secondary outcomes from the SWIFt randomised clinical trial

Abstract

Extended health benefits of a period of intermittent energy restriction in circadian-disrupted night-shift workers are unknown. We examined secondary 18-month outcomes of the SWIFt trial; a three-arm, parallel-group randomised controlled trial. Night-shift workers ( n  = 250) were randomised 1:1:1 to 24 weeks of moderate (20%) energy restriction; daily (continuous energy restriction; CER); or modified intermittent fasting on two days per week, undertaken on days off/day shifts (IF:2D) or during night shifts (IF:2N). The primary endpoint was reported previously. Outcomes of body weight, HOMA-IR and cardiometabolic risk factors were assessed 18 months after study enrolment, which was 12 months after completion of the supported intervention period. Analyses used the intention-to-treat principle. ANZCTR ACTRN-12619001035112 (19/07/2019). Here we show that at 18 months, mean difference in weight and HOMA-IR does not appear to differ between groups: weight, IF:2D versus CER = 2·7 kg [95% CI −3·6 to 9·2] and IF:2N versus CER = 0·9 kg [95% CI −5·6 to 7·3]; HOMA-IR, IF:2D versus CER = 0·7 [95% CI −0·3 to 1·7] and IF:2N versus CER = 0·7 [95% CI −0·2 to 1·7]. Between group differences are not observed in other cardiometabolic measures. Within-group body weight remains lower than baseline: CER: −4.8 kg [95% CI −6.1 to −3.1], IF:2D: −4.5 kg [−6.3 to −2.8], IF:2N: −3.2 kg [−5.1 to −1.04]. Attrition is similar between groups, with 141 participants providing data at 18 months. Findings indicate no apparent difference between strategies at 18 months, although the study may have insufficient power to detect small but clinically meaningful effects.