Time-Restricted Eating as a Nutrition Strategy for Individuals with Type 2 Diabetes: A Feasibility Study

Abstract

Individuals with type 2 diabetes (T2D) require a long-term dietary strategy for blood glucose management and may benefit from time-restricted eating (TRE, where the duration between the first and last energy intake is restricted to 8-10 h/day). We aimed to determine the feasibility of TRE for individuals with T2D. Participants with T2D (HbA1c >6.5 to <9%, eating window >12 h/day) were recruited to a pre-post, non-randomised intervention consisting of a 2-week Habitual period to establish baseline dietary intake, followed by a 4-weeks TRE intervention during which they were instructed to limit all eating occasions to between 10:00 and 19:00 h on as many days of each week as possible. Recruitment, retention, acceptability, and safety were recorded throughout the study as indicators of feasibility. Dietary intake, glycaemic control, psychological well-being, acceptability, cognitive outcomes, and physiological measures were explored as secondary outcomes. From 594 interested persons, and 27 eligible individuals, 24 participants enrolled and 19 participants (mean ± SD; age: 50 ± 9 years, BMI: 34 ± 5 kg/m², HbA1c: 7.6 ± 1.1%) completed the 6-week study. Overall daily dietary intake did not change between Habitual (~8400 kJ/d; 35% carbohydrate, 20% protein, 41% fat, 1% alcohol) and TRE periods (~8500 kJ/d; 35% carbohydrate, 19% protein, 42% fat, 1% alcohol). Compliance to the 9 h TRE period was 72 ± 24% of 28 days (i.e., ~5 days/week), with varied adherence (range: 4-100%). Comparisons of adherent vs. non-adherent TRE days showed that adherence to the 9-h TRE window reduced daily energy intake through lower absolute carbohydrate and alcohol intakes. Overall, TRE did not significantly improve measures of glycaemic control (HbA1c -0.2 ± 0.4%; p = 0.053) or reduce body mass. TRE did not impair or improve psychological well-being, with variable effects on cognitive function. Participants described hunger, daily stressors, and emotions as the main barriers to adherence. We demonstrate that 4-weeks of TRE is feasible and achievable for these individuals with T2D to adhere to for at least 5 days/week. The degree of adherence to TRE strongly influenced daily energy intake. Future trials may benefit from supporting participants to incorporate TRE in regular daily life and to overcome barriers to adherence.

Keywords: cognitive function; dietary adherence; energy restriction; glycaemic control; intermittent fasting; psychological well-being.

Figure 1

Schematic overview of study protocol. Participants completed a two-week Habitual baseline monitoring period (Week 0–2), immediately followed by a four-week intervention period of time-restricted eating (TRE; Week 2–6; consuming energy within 10:00 and 19:00 h on as many days of the week as possible) with weekly visits to the research team. Dietary recordings were collected throughout the entire 6-week period. A mixed-meal tolerance test (MMTT) and psychological questionnaires were conducted at the beginning of the Habitual (Visit 2) and end of the TRE (Visit 7) periods. Weekly, fasted blood samples were obtained from Visits 3–7. Physiological measures (body composition (dual-energy x-ray absorptiometry (DXA)), resting metabolic rate (RMR) and blood pressure (BP)) were conducted at the end of the Habitual (Visit 3) and TRE (Visit 7) periods, with a qualitative interview at the end of the TRE period (Visit 8).

Figure 2

Consolidated Standards of Reporting Trials (CONSORT) flow diagram of participant inclusions.

Figure 3

(A) Time of eating occasions during Habitual (○ n = 1089; 2 weeks) and time-restricted eating (TRE; △ n = 2051; 4 weeks) periods and (B) mean ± SD energy accumulation across the day during Habitual (unfilled bars) and TRE (filled bars). Significance (p < 0.05) * between periods (Habitual vs. TRE) within time points, from linear mixed model analysis with Bonferroni post hoc tests.

Figure 4

Concentrations and total area under the curve (AUC) of glucose (A,B) and insulin (C,D) in response to a mixed meal tolerance test (20% total daily energy requirements; 50% CHO, 30% fat, 20% protein) conducted at baseline (Habitual) and after a 4-week time-restricted eating (TRE) intervention for individuals with type 2 diabetes and overweight/obesity.