Purpose: Intermittent energy restriction (IER) is a popular weight loss (WL) strategy; however, its efficacy in clinical practice remains unknown. The present study compared the effects of IER compared to continuous energy restriction (CER) on WL and cardiometabolic risk factors in primary care.
Methods: A (self-selected) cohort study was conducted at the Rotherham Institute for Obesity (RIO), a primary care-based weight management service. 197(24% male) obese patients volunteered to participate and selected their diet group. IER participants (n = 99) consumed ~ 2600 kJ for two days/week. CER participants (n = 98) restricted their diet by ~ 2100 kJ/day below estimated requirements. Both interventions were delivered alongside RIO standard care. Changes in anthropometry and cardiometabolic disease risk markers (fasting biochemistry and blood pressure) were assessed after a 6-month intervention period and then participants were followed up again 6 months later (month 12).
Results: 27 IER patients (27%) and 39 CER patients (40%) completed the 6-month weight loss phase. Among completers, mean (SEM) WL was greater in the IER group at 6 months (5.4 ± 1.1% versus 2.8 ± 0.6%; p = 0.01), as were reductions in fat mass (p < 0.001) and improvements in systolic blood pressure (p < 0.001). Fasting insulin (p = 0.873) and diastolic blood pressure (p = 0.701) were reduced similarly in both groups. However, in the IER group, changes in anthropometry and blood pressure in the IER group had reverted to baseline by 12-month follow-up, whilst the CER group maintained weight loss but showed an increase in blood pressure.
Conclusions: Among completers, IER resulted in superior short-term changes in anthropometry and some cardiometabolic risk factors. However, rates of attrition and weight regain were higher compared with standard care, providing important insights in the implementations of IER within a "real-life" NHS setting.
Trial registration number: ISRCTN31465600.
Keywords: Glucose; Intermittent energy restriction; Intermittent fasting; Lipids; Primary care; Weight loss.