In recent years, time-restricted eating (TRE) has gained popularity as a strategy for weight loss and metabolic health (1) . TRE is associated with a spontaneous reduction in energy intake, comparable to calorie restriction diets (2) . Beyond energy intake, there is a lack of robust research into the effects of engaging in TRE on diet composition, quality and eating behaviours (3) . Such measures have been included as secondary outcomes or in analyses of pre-existing data in a small number of studies, with inconsistent results. Moreover, there is a lack of research on the effect of TRE on the nutritional status of vegans, who are already at risk of several nutrient deficiencies (4) . The overall aim of this study is to compare the effect of TRE on diet composition and quality, and eating behaviours in people following a vegan and an unrestricted diet. The aim of this abstract is to present preliminary findings on the effect of TRE on those following an unrestricted diet. In this ongoing pre- and post- design, healthy adults following a vegan or an unrestricted diet undertake TRE for four weeks, consuming all their meals within an 8-hour window (12pm-8pm) with calorie-free drinks allowed during the fasting window only. Participants are trained to complete food diaries and asked to record 3-day intake at baseline and in weeks 2 and 4 of TRE. Diet composition is analysed using Nutritics nutrition analysis software. Preliminary results from twelve participants with an unrestricted diet (33.6 ± 12.4 yrs, 10 female) who have completed the study to date show a significant reduction in energy intake from baseline by week 4 of TRE (p=.003). Participants consumed less fat (p=.025), saturated fat (p=.019), carbohydrate (p=.0009) and sugar (p=.009) in week 4, however, there was no significant difference from baseline when intake was expressed as a proportion (%) of energy intake. There was a reduction in absolute (grams per day) and relative (grams per kilogram per day) protein intake at week 4 (p=.003 and p=.004), as well as in fibre consumption (p=.034). Data from vegan participants is not reported due to insufficient numbers recruited to date. The simplicity of ‘watching the clock’ makes TRE an appealing approach for weight loss. Nevertheless, diet quality remains an important aspect of metabolic health but one which has been understudied in this context. Our preliminary findings indicate that the reduced eating opportunities during TRE may result in complex changes in diet composition. The reduced fibre consumption, which was already below the recommended daily intake at baseline, suggests that TRE may lead to detrimental changes to certain indicators of diet quality. Analysis of the full dataset will elucidate whether a vegan diet may predispose to a greater risk of disadvantageous changes to diet quality in comparison to those undertaking TRE with an unrestricted diet at baseline.
Petkova et al. (Fri,) studied this question.