Abstract
There is increasing interest for the use of intermittent energy restriction (IER) in weight management. However, there are concerns that IER could result in ‘rebound’ overconsumption of energy on unrestricted days. We studied self‐reported food records from participants in two trials of IER versus continuous energy restriction (Study 1; 44 women on IER for 6 months and Study 2; 72 women on two types of IER for 4 months). Energy intake was assessed on restricted and unrestricted days immediately before and after restricted days and on other unrestricted days. We assessed consistency of days of the week chosen as restricted days, and whether this was associated with greater weight loss. Reported energy intake was reduced on unrestricted days in Study 1 and 2 and was 19% lower compared with the allocated isoenergetic diet, and respectively 21% and 29% lower than their baseline reported daily intakes. Energy intake appeared to be similarly reduced the day immediately before and after restricted days and on other unrestricted days. Seventy percent of women in Study 1 and 79% in Study 2 undertook consistent days of restriction each week (>50% of restricted days on the same 2 days each week). When studies were combined percentage weight loss at 3 months was −5.8 (−6.7 to −4.7) % in the consistent group and −7.4 (−8.7 to −6.2) % in the non‐consistent group (p = .09). Food records from patients undertaking IER suggest a spontaneous reduction in energy intake below their baseline reported intakes and the prescribed isoenergetic diet during all unrestricted days including the days immediately before and after restricted days which contributes to the weight loss success with these diets. Consistency of restricted days was not associated with weight loss success. These findings need to be confirmed in larger groups of patients ideally using objective measures of energy balance.
Highlights
Contrary to concerns of compensatory energy increase on unrestricted days this self-report data finds an apparent relatively large spontaneous 19% reduction in energy intake below the allocated diet on unrestricted days, and below their baseline reported energy intake before commencing the diet
This apparent ‘carry over effect’ was seen across all unrestricted days in the food records including the days immediately before and after restricted days and is likely to be an important component contributing to the overall energy deficit and efficacy of intermittent energy restriction (IER) for weight loss
The lack of compensation of energy intake in our trial of subjects following an IER for weight loss is interesting and contrasts to previous short term fasting studies conducted in laboratory settings amongst subjects not attempting to lose weight
Summary
Dietary data were analysed from two previously published randomised trials of IER versus CER in overweight women previously reported by Harvie et al (2010, 2013). Study 2 tested two different versions of a 2 day IER for 3 months of weight loss and 1 month of weight maintenance (with one restricted day per week) amongst 75 pre and post menopausal women with overweight or obesity (BMI 24–45 kg/m2). In addition to 7 day food diaries participants in both trials were asked to complete simple weekly records throughout the whole study period to indicate if they had undertaken their restricted days that week and the precise timing of restricted days during the week. We included subjects allocated to IER in the two trials who had completed a baseline at least one 7 day food diary during the IER period. All participants included from Study 1 completed their two restricted days on consecutive days as shown by food records. In Study 1 mean (95% CI) energy intake on restricted days was 2,966 (2,761–3,176) kJ/day; in Study 2 this was 2,895 (2,769–3,016) kJ/day for the energy restricted low carbohydrate IER group and 4,318 (4,062–4,577) kJ/ day for the ad lib low carbohydrate IER group
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