Effects of intermittent fasting on health markers in those with type 2 diabetes: A pilot study

Abstract

Aim: To determine the short-term biochemical effects and clinical tolerability of intermittent fasting (IF) in adults with type 2 diabetes mellitus (T2DM).

Methods: We describe a three-phase observational study (baseline 2 wk, intervention 2 wk, follow-up 2 wk) designed to determine the clinical, biochemical, and tolerability of IF in community-dwelling volunteer adults with T2DM. Biochemical, anthropometric, and physical activity measurements (using the Yale Physical Activity Survey) were taken at the end of each phase. Participants reported morning, afternoon and evening self-monitored blood glucose (SMBG) and fasting duration on a daily basis throughout all study stages, in addition to completing a remote food photography diary three times within each study phase. Fasting blood samples were collected on the final days of each study phase.

Results: At baseline, the ten participants had a confirmed diagnosis of T2DM and were all taking metformin, and on average were obese [mean body mass index (BMI) 36.90 kg/m2]. We report here that a short-term period of IF in a small group of individuals with T2DM led to significant group decreases in weight (-1.395 kg, P = 0.009), BMI (-0.517, P = 0.013), and at-target morning glucose (SMBG). Although not a study requirement, all participants preferentially chose eating hours starting in the midafternoon. There was a significant increase (P < 0.001) in daily hours fasted in the IF phase (+5.22 h), although few attained the 18-20 h fasting goal (mean 16.82 ± 1.18). The increased fasting duration improved at-goal (< 7.0 mmol/L) morning SMBG to 34.1%, from a baseline of 13.8%. Ordinal Logistic Regression models revealed a positive relationship between the increase in hours fasted and fasting glucose reaching target values (χ2 likelihood ratio = 8.36, P = 0.004) but not for afternoon or evening SMBG (all P > 0.1). Postprandial SMBGs were also improved during the IF phase, with 60.5% readings below 9.05 mmol/L, compared to 52.6% at baseline, and with less glucose variation. Neither insulin resistance (HOMA-IR), nor inflammatory markers (C-reactive protein) normalized during the IF phase. IF led to an overall spontaneous decrease in caloric intake as measured by food photography (Remote Food Photography Method). The data demonstrated discernable trends during IF for lower energy, carbohydrate, and fat intake when compared to baseline. Physical activity, collected by a standardized measurement tool (Yale Physical Activity Survey), increased during the intervention phase and subsequently decreased in the follow-up phase. IF was well tolerated in the majority of individuals with 6/10 participants stating they would continue with the IF regimen after the completion of the study, in a full or modified capacity (i.e., every other day or reduced fasting hours).

Conclusion: The results from this pilot study indicate that short-term daily IF may be a safe, tolerable, dietary intervention in T2DM patients that may improve key outcomes including body weight, fasting glucose and postprandial variability. These findings should be viewed as exploratory, and a larger, longer study is necessary to corroborate these findings.

Keywords: Homeostasis model of assessment for insulin resistence index; Intermittent fasting; Remote food photography; Self-monitored blood glucose; Type 2 diabetes.

Conflict of interest statement

Conflict-of-interest statement: There are no conflicts of interest to report.

Figures

Figure 1

Study design. During the three-phase, 6 wk study, participants engaged in normal dietary patterns (breakfast, lunch and dinner) during weeks 1-2 (Phase 1, baseline) and 5-6 (Phase 3, follow-up). For weeks 3-4 (Phase 2, intervention) participants followed the IF meal timing pattern with a goal of daily fasts for 18-20 h per day, and a 4-6 h feeding period. Ad libidum zero-calorie intake, including coffee and tea during fasting hours, was permitted. Hours fasted and self-monitored blood glucose (fasted a.m., random afternoon pre-meal, postprandial evening) was reported daily throughout the study. On the last day (day 14, 28 and 42) of each phase, biochemical (fasting bloodwork), anthropomorphic (clinical assessment), and YPAS physical activity was collected. A 3-d consecutive photographic food diary was collected during each of the three phases. YPAS: Yale Physical Activity Survey; IF: Intermittent fasting.

Figure 2

Intermittent Fasting improves morning fasted glucose levels and decreases postprandial variability. The daily means for fasting morning glucose levels (from personal glucometers) on days 1 through 42 are shown in Figure 2A, with the three phases indicated. Means were calculated from pooled SMBG data from the nine individuals that provided complete log sets. Figure 2B represents the daily variance from the mean for fasting morning SMBG, days 1-42, using the Kolmogorov-Smirnov (KS) test. Figure 2C shows the daily variance from the mean for evening postprandial SMBG values on days 1-42. Inflection points of quadratic equations were calculated using the formula [f 1 (y) of C + Ax + B × 2 = 0] rounded down to the nearest full integer. A: Mean morning fasted SMBG; B: Morning fasted SMBG variability; C: Evening random SMBG variability. SMBG: Self-monitored blood glucose.

Figure 3

Positive relationship between hours fasted and morning glucose levels. Ordinal logistic regression (OLR) tested the association between the increase in hours fasted from baseline, and the morning fasting glucose levels within the four glucose ranges noted. OLR was performed using data from the 8 individuals who had completed both their full SMBG logs and daily hours fasted logs. OLR models used the non-equalized data. Hours Fasted Difference (HFD) was calculated for baseline and intervention phases only. SMBG: Self-monitored blood glucose.