Original Investigation | Nutrition, Obesity, and Exercise

Effect of Time-Restricted Eating on Weight Loss in Adults With Type 2 Diabetes
A Randomized Clinical Trial
Vasiliki Pavlou, MS, RD; Sofia Cienfuegos, PhD; Shuhao Lin, MS, RD; Mark Ezpeleta, PhD; Kathleen Ready, MS, RD; Sarah Corapi, MS; Jackie Wu, MS, RD; Jason Lopez, BS;
Kelsey Gabel, PhD, RD; Lisa Tussing-Humphreys, PhD, RD; Vanessa M. Oddo, PhD; Shaina J. Alexandria, PhD; Julienne Sanchez, MD; Terry Unterman, MD;
Lisa S. Chow, MD, MS; Alaina P. Vidmar, MD; Krista A. Varady, PhD

Abstract

Key Points

IMPORTANCE Time-restricted eating (TRE) has become increasingly popular, yet longer-term
randomized clinical trials have not evaluated its efficacy and safety in patients with type 2

Question Is time-restricted eating
(TRE) without calorie counting more
effective for weight loss and lowering of

diabetes (T2D).

hemoglobin A1c (HbA1c) levels compared

OBJECTIVE To determine whether TRE is more effective for weight reduction and glycemic control
than daily calorie restriction (CR) or a control condition in adults with T2D.

with daily calorie restriction (CR) in
adults with type 2 diabetes (T2D)?
Findings In a 6-month randomized

DESIGN, SETTING, AND PARTICIPANTS This 6-month, parallel-group, randomized clinical trial was

clinical trial involving 75 adults with T2D,

performed between January 25, 2022, and April 1, 2023, at the University of Illinois Chicago.

TRE was more effective for weight loss

Participants were aged 18 to 80 years with obesity and T2D. Data analysis was based on intention

(−3.6%) than CR (−1.8%) compared with

to treat.

controls. However, changes in HbA1c
levels did not differ between the TRE

INTERVENTIONS Participants were randomized to 1 of 3 groups: 8-hour TRE (eating 12 to 8 PM only,

(−0.91%) and CR (−0.94%) groups

without calorie counting), CR (25% energy restriction daily), or control.

compared with controls.
Meaning These findings suggest that

MAIN OUTCOMES AND MEASURES The primary outcome measure was change in body weight by
month 6. Secondary outcomes included changes in hemoglobin A1c (HbA1c) levels and metabolic
risk factors.

time-restricted eating may be an
effective alternative strategy to CR for
lowering body weight and HbA1c levels
in T2D.

RESULTS Seventy-five participants were enrolled with a mean (SD) age of 55 (12) years. The mean
(SD) body mass index (calculated as weight in kilograms divided by height in meters squared) was 39
(7) and the mean (SD) HbA1c level was 8.1% (1.6%). A total of 53 participants (71%) were women. One
participant (1%) was Asian, 30 (40%) were Hispanic White, 40 (53%) were non-Hispanic Black, and
4 (5%) were non-Hispanic White. Participants in the TRE group were adherent with their eating
window on a mean (SD) of 6.1 (0.8) days per week, and 17 (68%) in the CR group were adherent with

+ Visual Abstract
+ Supplemental content
Author affiliations and article information are
listed at the end of this article.

their prescribed calorie goals over 6 months. The mean (SD) reduction in energy intake was −313
(509) kcal/d for TRE, −197 (426) kcal/d for CR, and −16 (439) kcal/d for controls. By month 6, body
weight decreased significantly in the TRE group (−3.56% [95% CI, −5.92% to −1.20%]; P = .004) but
not the CR group (−1.78% [95% CI, −3.67% to 0.11%]; P = .06), relative to controls. Levels of HbA1c
decreased in the TRE (−0.91% [95% CI, −1.61% to −0.20%]) and CR (−0.94% [95% CI, −1.59% to
−0.30%]) groups, relative to controls, with no differences between the TRE and CR groups. Time in
euglycemic range, medication effect score, blood pressure, and plasma lipid levels did not differ
among groups. No serious adverse events were reported.
CONCLUSIONS AND RELEVANCE This randomized clinical trial found that a TRE diet strategy
without calorie counting was effective for weight loss and lowering of HbA1c levels compared with
(continued)

Open Access. This is an open access article distributed under the terms of the CC-BY-NC-ND License.
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Effect of Time-Restricted Eating on Weight Loss in Adults With Type 2 Diabetes

Abstract (continued)

daily calorie counting in a sample of adults with T2D. These findings will need to be confirmed by
larger RCTs with longer follow-up.
TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT05225337
JAMA Network Open. 2023;6(10):e2339337. doi:10.1001/jamanetworkopen.2023.39337

Introduction
Approximately 1 in 10 US residents have type 2 diabetes (T2D).1 If current trends continue, 1 in 3 US
adults will have T2D by 2050.1 Innovative lifestyle strategies to treat T2D are critically needed.
Calorie restriction (CR) is generally encouraged as the first line of therapy to help people with T2D
achieve their weight management goals and glycemic targets.2 However, many patients find it
difficult to adhere to CR because calorie intake must be vigilantly monitored every day. Another
approach that limits the timing of food intake instead of the number of calories consumed has
recently been popularized. This diet is termed time-restricted eating (TRE) and involves confining
daily food intake to 6 to 10 hours and fasting for the remaining hours. Evidence shows that limiting
the eating window to 6 to 10 hours within a 24-hour period naturally reduces energy intake by 200
to 500 kcal/d.3-5 Moreover, since TRE allows individuals to self-select foods and eat freely during a
large part of the day, adherence remains high for up to 12 months.6 Therefore, TRE may be an
attractive alternative to CR for weight loss in patients with T2D.
Only 2 TRE trials7,8 to date have been conducted in adults with T2D. The preliminary findings of
these trials show that TRE reduced body weight by 1% to 4%, lowered hemoglobin A1c (HbA1c) levels
by 1.5%, and increased time spent in the euglycemic range compared with controls.7,8 However,
these trials were limited by short duration (3-12 weeks) and lack of comparison with standard care (ie,
daily CR).
Accordingly, we conducted a 6-month, randomized clinical trial comparing the effects of 8-hour
TRE (eating all food between 12:00 PM and 8:00 PM, without calorie counting) with CR (25%
restriction daily) and a control condition on body weight and glycemic control in a group of adults
with T2D and obesity. We hypothesized that the TRE group would achieve greater weight loss and
larger reductions in HbA1c levels, compared with a CR group and a control group.

Methods
The protocol for this randomized clinical trial was approved by the Office for the Protection of
Research Subjects at the University of Illinois Chicago, and written informed consent was obtained
from all participants. The full trial protocol and statistical analysis plan are provided in Supplement 1.
This study followed the Consolidated Standards of Reporting Trials (CONSORT) reporting guidelines.

Trial Participants
The trial was a 6-month, single-center, randomized clinical trial conducted at the University of Illinois
Chicago between January 25, 2022, and April 1, 2023 (eFigure 1 in Supplement 2). Inclusion criteria
were as follows: previous diagnosis of T2D, HbA1c levels between 6.5% and 11.0% (to convert to
proportion of total hemoglobin, multiply by 0.01), 18 to 80 years of age, and body mass index (BMI;
calculated as weight in kilograms divided by height in meters squared) between 30 and 50. Exclusion
criteria consisted of unstable weight for 3 months prior to the beginning of the study (>4% weight
loss or gain), history of eating disorders, eating within less than a 10-hour window at baseline,
nightshift work, pregnant or trying to become pregnant, and current smoking. Self-reported race and

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Effect of Time-Restricted Eating on Weight Loss in Adults With Type 2 Diabetes

ethnicity data (including Asian, Hispanic White, non-Hispanic Black, and non-Hispanic White) were
collected given that Hispanic and non-Hispanic Black adults have a high prevalence of T2D in the US.

Randomization and Blinding
Participants were randomized in a 1:1:1 ratio to a TRE, CR, or control group. Randomization was
performed by a stratified random sampling procedure by sex, age (18-49 and 50-80 years), BMI
(30-39 and 40-50), and HbA1c level (6.50%-8.75% and 8.76%-11.00%). Participants were
not blinded.

Intervention Groups
Participants in the TRE group ate ad libitum between 12:00 and 8:00 PM daily and fasted from 8:00
PM to 12:00 PM the following day. During the 8-hour eating window, participants were not required

to monitor caloric intake, and there were no restrictions on types or quantities of food consumed.
During the 16-hour fasting window, participants were encouraged to drink plenty of water and were
permitted to consume energy-free drinks. Participants self-monitored adherence to the eating
window using a log in which they recorded the times that they started and stopped eating each day.
Participants in the CR group were instructed to reduce their energy intake by 25% of their
baseline energy needs every day. Total energy expenditure was calculated using the Mifflin
equation.9 Participants met with a study dietitian (V.P.) at the beginning of the trial to develop
individualized weight loss meal plans and self-monitored adherence to their calorie target by logging
food intake into an app every day.
Control participants were instructed to maintain their weight and usual eating and exercise
habits. Control participants visited the research center at the same frequency as the intervention
participants to provide outcome measurements.
Participants in the TRE, CR, and control groups met with the study dietitian weekly from
baseline to month 3 (by telephone or Zoom) and then biweekly thereafter. Body weight, adherence,
medication changes, and adverse events were recorded during these calls. Participants in the TRE
and CR groups were also taught how to make general healthy food choices that conform to American
Diabetes Association nutrition guidelines.2 All participants were instructed not to change their
physical activity habits throughout the trial.

Medication Management
The medication management protocol was developed based on the literature.10,11 If the participant’s
baseline HbA1c level was below 7.0%, sulfonylureas were discontinued, the dose of short-acting
insulin was reduced by 50%, and the dose of long-acting remained unchanged. If the participant’s
baseline HbA1c level was greater than 7.0% but below 8.5%, the dose of sulfonylureas was reduced
by 50%, the dose of short-acting insulin was reduced by 10%, and the dose of long-acting insulin
remained unchanged. If the participant’s baseline HbA1c level was greater than 8.5%, doses of
sulfonylurea, short-acting insulin, and long-acting insulin remained unchanged. No medication
adjustments were made for controls.

Blood Glucose Level Monitoring
All participants wore a continuous glucose monitor (CGM [Dexcom G7; DexCom, Inc]) for 10 days at
baseline, month 3, and month 6. The CGM data were used to detect hypoglycemic (glucose level <70
mg/dL [to convert to mmol/L, multiply by 0.0555]) or hyperglycemic (glucose level >180 mg/dL)
events. When participants were not wearing the CGM, they tested their blood glucose levels daily
using a lancing device and glucose monitor.

Outcome Measures
The primary outcome of the study was percentage change in body weight among the TRE, CR, and
control groups by month 6. Secondary outcomes included changes in HbA1c levels, time in
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euglycemic range (glucose levels 70-180 mg/dL), mean glucose level (measured by CGM),
medication effect score,12 body composition (measured by dual-energy x-ray absorptiometry), blood
pressure and heart rate, plasma lipid levels, dietary intake (measured by the ASA-24 [automated
self-administered 24-hour] dietary assessment tool13), dietary adherence, physical activity (steps per
day), and weekly adverse events among the TRE, CR, and control groups by month 6. Analytical
methods are detailed in Supplement 1. Reporting of serious adverse events followed requirements
mandated by the University of Illinois Office for Protection of Research Subjects (Supplement 1).

Statistical Analysis
For the sample size calculation, we estimated that TRE and CR groups would reduce body weight by
7% and 3%, respectively, by month 6 compared with controls (estimated no change in body weight).
We calculated that 21 participants per group would provide 80% power to detect a significant
difference in body weight among the TRE, CR, and control groups by month 6, using an overall F test
from a 1-way analysis of variance with α = .05, effect size of 0.4096, and a common SD of 7%. We
anticipated a dropout rate of 15%.4 Thus, we aimed to recruit 75 participants (25 per group),
assuming that 63 participants (21 per group) would complete the trial.
Data are shown as mean (95% CI) unless otherwise noted. A Bonferroni-adjusted 2-tailed P <
.017 was considered statistically significant for pairwise group comparisons of percentage change in
body weight. P values generated from analyses of secondary outcomes were not adjusted for
multiplicity and are considered descriptive. We conducted an intention-to-treat analysis, which
included data from all 75 participants who underwent randomization. Results are reported by
intention-to-treat analysis unless indicated otherwise.
A linear mixed model was used to assess time, group, and time × group effects for each
outcome. In each model, time and group effects (and their interaction) were estimated without
imposing a linear time trend. In models for body weight, which was measured at 7 time points
(baseline and each of 6 months of follow-up), time was modeled with cubic splines. In models of all
other outcome variables, which were measured at 2 time points (baseline and month 6), time was
modeled as a categorical variable. All models were adjusted for baseline use of sodium-glucose
transport protein 2 inhibitors and glucagon-like peptide-1 receptor agonists to account for empirical
baseline differences in medication use between treatment groups.
For each outcome variable, linear modeling assumptions were assessed with residual diagnostics.
To account for the potential of nonuniform variances (heteroskedasticity) between treatment groups
due to random chance, all CIs and P values from linear mixed models were calculated using robust
variance estimators (sandwich estimators).14-16 Intraclass correlation coefficients from each linear mixed
effect were also calculated. To assess the effect of loss to follow-up on study findings, we conducted a
sensitivity analysis using multiple imputation. Multiple imputation can incorporate observed data not
otherwise accounted for in the model (eg, using baseline insulin levels to impute missing time in
euglycemic range) to estimate multiple values for each missing data point and account for sampling
variability. Missing follow-up data were imputed under the assumption that systematic differences
between missing and observed outcomes can be explained by baseline values of the outcome as well as
baseline values of height and waist circumference (and medication effect score and HbA1c level for
glycemic outcomes), and all previous time points of weight. All analyses were performed using R
software, version 4.3.1 (R Project for Statistical Computing).

Results
Trial Participants
We screened 127 people and enrolled 75 participants (Figure 1). Participants had a mean (SD) age of
55 (12) years, mean (SD) BMI of 39 (7), and mean (SD) HbA1c level of 8.1% (1.6%). Fifty-three
participants (71%) were women and 22 (29%) were men. One participant (1%) was Asian, 30 (40%)
were Hispanic White, 40 (53%) were non-Hispanic Black, and 4 (5%) were non-Hispanic White
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(Table 1). The attrition rate (ie, participants lost to follow-up) was 2 (8%) in the TRE group, 3 (12%) in
the CR group, and 1 (4%) in the control group. The reasons for participant attrition included personal
reasons, inability to contact, not wanting to be in the control group, and motor vehicle crash.

Weight Loss and Body Composition
By month 6, mean body weight significantly decreased in the TRE group (−3.56% [95% CI, −5.92%
to −1.20%]; P = .004) but not the CR group (−1.78% [95% CI, −3.67% to 0.11%]; P = .06), relative to
controls (Figure 2A and Table 2). Fat mass decreased in the TRE group by month 6 (−2.49 [95% CI,
−4.41 to −0.58] kg) but not the CR group (−1.65 [95% CI, −3.33 to 0.04] kg), relative to controls
(Table 2). Both TRE and CR led to reductions in waist circumference by month 6, but not lean mass or
visceral fat mass, compared with controls. Relative to controls, BMI decreased in the TRE group by
month 6, but not the CR group.

Glycemic Control and Medication Effect Score
By month 6, mean HbA1c levels were reduced in the TRE group (−0.91% [95% CI, −1.61% to −0.20%])
and CR group (−0.94% [95% CI, −1.59% to −0.30%]), relative to controls, with no differences between
the TRE and CR group (0.04% [95% CI, −0.64% to 0.72%]) (Figure 2B and Table 2). Mean glucose levels
decreased in the TRE group (−42.53 [95% CI, −79.73 to −5.33] mg/dL) and CR group (−48.55 [95% CI,
−85.55 to −11.54] mg/dL), relative to controls, with no differences between the TRE and CR groups (6.02
[95% CI, −12.67 to 24.70] mg/dL) (Figure 2C and Table 2). Time in the euglycemic range and medication
effect scores were not associated with treatment group in any pairwise comparisons at month 6
(Table 2). Medication use at baseline and month 6 is reported in eTable 1 in Supplement 2.

Sensitivity Analysis Using Multiple Imputation
Conclusions for body weight and HbA1c level did not change from the primary analyses to the
sensitivity analyses (eTable 2 in Supplement 2), demonstrating that the results are robust to
misspecification of the missingness mechanism. However, sensitivity analyses differed from primary
analyses for some secondary outcomes: fat mass decreased in both the TRE and the CR groups by
month 6 relative to controls (rather than in the TRE group alone), and mean glucose levels decreased
in the CR group only. Conclusions did not change between the primary analysis and sensitivity
analysis for any other secondary outcome.

Figure 1. Study Flowchart
127 Individuals screened

52 Excluded
38 Did not meet 1 or more
inclusion criteria
14 Declined to participate

75 Randomized

25 Randomized to timerestricted eating

2 Withdrew
1 Personal reasons
1 Unable to contact

23 Completed 6 mo
of intervention

25 Randomized to daily
calorie restriction

3 Withdrew
1 Motor vehicle crash
2 Unable to contact

22 Completed 6 mo
of intervention

25 Randomized to
control group

1 Withdrew
1 Did not want to
be in control group

24 Completed 6 mo
of intervention

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Plasma Lipid Levels and Blood Pressure
Changes in blood pressure, heart rate, total cholesterol, LDL cholesterol, HDL cholesterol, and
triglyceride concentrations were observed. However, these changes were not associated with
treatment group in any pairwise comparisons at month 6 (Table 2).
Table 1. Baseline Characteristics of the Study Participantsa
Participant group
Characteristic
Age, y

Study completion

TRE (n = 25)
56 (13)

CR (n = 25)
55 (13)

Control (n = 25)
54 (11)

All (N = 75)
55 (12)

Completed (n = 69)
56 (12)

Dropped out (n = 6)
46 (10)

Women

18 (72)

17 (68)

18 (72)

53 (71)

51 (74)

2 (33)

Men

7 (28)

8 (32)

7 (28)

22 (29)

18 (26)

4 (67)

Asian

0

1 (4)

0

1 (1)

0

1 (17)

Hispanic White

10 (40)

9 (36)

11 (44)

30 (40)

27 (39)

3 (50)

Non-Hispanic Black

12 (48)

14 (56)

14 (56)

40 (53)

38 (55)

2 (33)

Non-Hispanic White

3 (12)

1 (4)

0

4 (5)

4 (6)

0

15 (11)

14 (9)

12 (9)

14 (9)

14 (9)

5 (4)

Metformin

21 (84)

19 (76)

21 (84)

61 (81)

57 (83)

4 (67)

DPP-4 inhibitors

0

4 (16)

1 (4)

5 (7)

5 (7)

0

SGLT-2 inhibitors

9 (36)

1 (4)

5 (20)

15 (20)

14 (20)

1 (17)

GLP-1 receptor agonists

8 (32)

5 (20)

6 (24)

19 (25)

18 (26)

1 (17)

Sulfonylureas

2 (8)

7 (28)

2 (8)

11 (15)

9 (13)

2 (33)

13 (52)

4 (16)

9 (36)

26 (35)

25 (36)

1 (17)

Sex, No. (%)

Race and ethnicity, No. (%)

T2D duration, y
Diabetes medications, No. (%)
Oral hypoglycemic agents

Insulin
Medication effect scoreb
Oral hypoglycemic agents

1.3 (0.7)

1.0 (0.8)

1.3 (0.9)

1.2 (0.8)

1.2 (0.8)

1.2 (1.1)

Insulin

0.5 (0.7)

0.2 (0.5)

0.3 (0.6)

0.4 (0.6)

0.4 (0.6)

0.2 (0.6)

Body weight, kg

105 (25)

104 (17)

107 (22)

105 (21)

105 (22)

108 (16)

Height, cm

165 (7)

166 (10)

165 (8)

165 (8)

165 (8)

171 (10)

BMI

39 (9)

38 (5)

39 (7)

39 (7)

39 (7)

37 (4)

HbA1c level, %

8.3 (2.0)

8.1 (1.5)

7.9 (1.3)

8.1 (1.6)

8.0 (1.6)

8.6 (1.7)

Time in euglycemic range, %

63 (30)

60 (30)

62 (32)

62 (30)

64 (30)

37 (15)

Glucose level, mg/dL

180 (47)

183 (59)

177 (58)

180 (54)

178 (56)

203 (20)

Fat mass, kg

43 (10)

49 (10)

47 (14)

46 (11)

46 (12)

46 (9)

Lean mass, kg

54 (13)

52 (10)

53 (10)

53 (11)

52 (9)

56 (20)

Visceral fat mass, kg

1.9 (0.7)

2.5 (1.0)

2.2 (0.9)

2.2 (0.9)

2.2 (0.9)

2.4 (1.3)

Waist circumference, cm

117 (13)

120 (9)

121 (15)

120 (13)

120 (13)

118 (10)
135 (19)

Body composition

Blood pressure, mm Hg
SBP

135 (17)

137 (17)

131 (20)

134 (18)

134 (18)

DBP

85 (12)

87 (13)

85 (9)

86 (11)

85 (11)

90 (15)

78 (14)

79 (13)

80 (12)

79 (13)

78 (13)

85 (14)

Total cholesterol

164 (44)

171 (43)

163 (39)

166 (42)

165 (43)

174 (27)

LDL cholesterol

90 (37)

92 (36)

94 (37)

92 (36)

92 (37)

94 (24)

HDL cholesterol

48 (12)

48 (14)

47 (9)

48 (12)

48 (12)

42 (6)

Triglycerides

130 (58)

144 (64)

121 (37)

132 (55)

127 (50)

189 (75)

Heart rate, bpm
Plasma lipid levels, mg/dL

Abbreviations: BMI, body mass index (calculated as weight in kilograms divided by height in meters squared); bpm, beats per minute; CR, calorie restriction; DBP, diastolic blood
pressure; DPP-4, dipeptidyl peptidase 4; GLP-1, glucagonlike peptide-1; HbA1c, hemoglobin A1c; HDL, high-density lipoprotein; LDL, low-density lipoprotein; SBP, systolic blood
pressure; SGLT-2, sodium-glucose transport protein 2; T2D, type 2 diabetes; TRE, time-restricted eating.
SI conversion factors: To convert cholesterol to mmol/L, multiply by 0.0258; glucose to mmol/L, multiply by 0.0555; HbA1c to proportion of total hemoglobin, multiply by 0.01;
triglycerides to mmol/L, multiply by 0.0113.
a

Unless otherwise indicated, data are expressed as mean (SD).

b

Calculated as (actual drug dose/maximum drug dose) × drug mean adjustment factor. A higher score corresponded to a higher dose of diabetes medication, and a reduction
corresponded to a reduction in diabetes medication.
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Effect of Time-Restricted Eating on Weight Loss in Adults With Type 2 Diabetes

Adherence and Energy Intake
The mean (SD) caloric deficit was −313 (509) kcal/d for the TRE group, −197 (426) kcal/d for the CR
group, and −16 (439) kcal/d for the control group over 6 months. Differences in dietary intake among
groups are given in Table 3. The TRE group reported being adherent with their eating window a mean
(SD) of 6.1 (0.8) days per week (87% of days) over 6 months (eFigure 2 in Supplement 2). In the CR
group, 17 participants (68%) reported being adherent with their prescribed calorie goals during the
6-month trial (eFigure 2 in Supplement 2). Participants in the TRE group reported finding their diet
intervention easier to adhere to compared with CR group participants (eFigure 3 in Supplement 2).

Daily Eating Window, Diet Quality, and Physical Activity
The daily eating window in the TRE group decreased from baseline to month 6 but remained
unchanged in the CR and control groups (Table 3). Dietary intake and physical activity did not differ
over time or between groups (Table 3).

Adverse Events
No serious adverse events were reported. Occurrences of hypoglycemia and hyperglycemia did not
differ between groups (eTable 3 in Supplement 2).

Figure 2. Change in Body Composition and Glycemic Control in the Study Groups
A Body weight

2

Weight loss, %

0

–2

–4

–6

Control
CR
TRE

–8
0

1

2

3

4

5

6

Study month
B

C

Mean HbA1c level
1.0

Mean glucose level
80

60

Change from baseline, %

Change from baseline, %

0.5

0

–0.5

40

20

0

–1.0
–20

–1.5

TRE

CR

Control

–40

TRE

CR

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Control

Data were included for 75 participants; means were
estimated using an intention-to-treat analysis using a
linear mixed model. Error bars indicate 95% CIs for
each parameter from baseline by diet group. CR
indicates calorie restriction; TRE,
time-restricted eating.

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75

Body weight, kg

67

67

Time in euglycemic
range, %

Mean glucose level,
mg/dL

75

Insulin

71

70

74

75

Lean mass, kg

Visceral fat mass, kg

Waist circumference, cm

BMI

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71

71

LDL cholesterol

HDL cholesterol

Triglycerides

60

60

60

60

65

65

65

68

67

64

65

65

69

69

56

56

66

68

68

6 mo

−15.43 (−37.92 to 7.06)

3.20 (0.88 to 5.52)

−0.23 (−9.56 to 9.10)

−0.18 (−10.55 to 10.20)

−2.48 (−6.79 to 1.84)

−2.88 (−6.92 to 1.16)

−4.45 (−9.98 to 1.07)

−1.78 (−2.63 to −0.94)

−3.92 (−5.93 to −1.91)

−0.16 (−0.36 to 0.05)

−0.97 (−2.04 to 0.10)

−2.77 (−4.36 to −1.18)

−0.02 (−0.10 to 0.07)

−0.12 (−0.26 to 0.01)

−11.02 (−24.85 to 2.82)

4.78 (−3.52 to 13.08)

−0.72 (−1.25 to −0.18)

−4.52 (−6.73 to −2.30)

−4.28 (−6.26 to −2.31)

TRE

−9.53 (−25.14 to 6.08)

−0.23 (−3.68 to 3.23)

−4.57 (−16.19 to 7.04)

−8.12 (−22.86 to 6.63)

−1.77 (−6.03 to 2.49)

−1.47 (−3.86 to 0.93)

−3.91 (−9.33 to 1.52)

−0.89 (−1.36 to −0.41)

−3.97 (−6.03 to −1.92)

−0.18 (−0.32 to −0.04)

−0.46 (−1.15 to 0.23)

−1.92 (−3.20 to −0.65)

−0.02 (−0.05 to 0.01)

0.04 (−0.15 to 0.23)

−17.03 (−30.49 to −3.58)

10.65 (2.65 to 18.65)

−0.75 (−1.20 to −0.30)

−2.63 (−3.99 to −1.27)

−2.50 (−3.83 to −1.18)

CR

Participant group, mean change from baseline (95% CI)

3.70 (−13.32 to 20.73)

1.02 (−1.57 to 3.62)

−4.86 (−16.76 to 7.05)

−1.88 (−15.67 to 11.90)

−0.84 (−6.44, to 4.75)

0.06 (−3.22 to 3.34)

1.52 (−4.45 to 7.49)

−0.37 (−0.95 to 0.22)

−0.48 (−1.66 to 0.71)

−0.07 (−0.18 to 0.04)

−0.59 (−1.49 to 0.32)

−0.28 (−1.46 to 0.90)

0.00 (0.00 to 0.00)

0.03 (−0.15 to 0.21)

31.51 (−4.54 to 67.56)

−7.81 (−24.90 to 9.27)

0.19 (−0.30 to 0.68)

−1.07 (−2.70 to 0.57)

−0.72 (−2.14 to 0.69)

Control

−5.90 (−32.3 to 20.59)

3.43 (−0.60 to 7.47)

4.34 (−10.04 to 18.73)

7.94 (−9.47 to 25.35)

−0.71 (−6.61 to 5.19)

−1.41 (−5.97 to 3.14)

−0.55 (−8.05 to 6.96)

−0.90 (−1.83 to 0.04)

0.05 (−2.74 to 2.84)

0.02 (−0.21 to 0.26)

−0.51 (−1.74 to 0.72)

−0.85 (−2.82 to 1.13)

0.01 (−0.08 to 0.09)

−0.16 (−0.38 to 0.06)

6.02 (−12.67 to 24.70)

−5.87 (−17.03 to 5.28)

0.04 (−0.64 to 0.72)

−1.89 (−4.42 to 0.64)

−1.78 (−4.09 to 0.53)

TRE vs CR

c

−19.13 (−46.42 to 8.16)

2.18 (−1.19 to 5.54)

4.63 (−9.99 to 19.24)

1.71 (−14.97 to 18.38)

−1.63 (−8.51 to 5.24)

−2.94 (−7.98 to 2.10)

−13.23 (−35.62 to 9.15)

−1.25 (−5.44 to 2.93)

0.28 (−15.81 to 16.38)

−6.23 (−25.76 to 13.30)

−0.93 (−7.77 to 5.91)

−1.52 (−5.46 to 2.41)

−5.43 (−13.25 to 2.39)

−0.52 (−1.25 to 0.21)

−1.41 (−2.41 to −0.42)c

−5.98 (−13.87 to 1.92)

−0.11 (−0.28 to 0.06)
−3.50 (−5.80 to −1.20)c

−3.44 (−5.71 to −1.18)c

0.13 (−0.98 to 1.23)

−1.65 (−3.33 to 0.04)

−0.02 (−0.05 to 0.01)

0.01 (−0.25 to 0.26)

−48.55 (−85.55 to
−11.54)c

18.46 (0.31 to 36.62)

−0.09 (−0.31 to 0.13)

−0.38 (−1.74 to 0.98)

−2.49 (−4.41 to −0.58)c

−0.02 (−0.10 to 0.07)

−0.15 (−0.37 to 0.07)

−42.53 (−79.73 to −5.33)

12.59 (−5.70 to 30.89)

-0.94 (−1.59 to −0.30)c

−1.56 (−3.63 to 0.51)

−0.91 (−1.61 to −0.20)c

−1.78 (−3.67 to 0.11)

−3.45 (−6.13 to −0.77)b

CR vs control

−3.56 (−5.92 to −1.20)b

TRE vs control

Mean difference between groups (95% CI)

Means were estimated using an intention-to-treat analysis using a linear mixed model with 95% CIs for each parameter from baseline by diet group.

Indicates statistical significance using Bonferroni-adjusted 2-tailed P < .017.

Indicates statistical significance using P < .05.

a

b

c

SI conversion factors: To convert cholesterol to mmol/L, multiply by 0.0258; glucose to mmol/L, multiply by 0.0555; HbA1c to proportion of total hemoglobin, multiply by 0.01; triglycerides to mmol/L, multiply by 0.0113.

Abbreviations: BMI, body mass index (calculated as weight in kilograms divided by height in meters squared); CR, calorie restriction; DBP, diastolic blood pressure; HbA1c, hemoglobin A1c; HDL, high-density lipoprotein; LDL,
low-density lipoprotein; OHA, oral hypoglycemic agent; SBP, systolic blood pressure; TRE, time-restricted eating.

71

71

Total cholesterol

Plasma lipid levels, mg/dL

75

75

DBP

Heart rate, bpm

75

SBP

Blood pressure, mm Hg

71

Fat mass, kg

Body composition

75

OHA

Medication effect score

72

HbA1c level, %

Glycemic control

75

Baseline

No. of participants

Body weight, % lost

Weight

Variable

Table 2. Body Weight, Glycemic Control, and Cardiometabolic Risk Factorsa

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Discussion
Findings of this randomized clinical trial show that 8-hour TRE produced greater weight loss when
compared with CR and a control condition. Despite the greater weight loss achieved by the TRE
group, reductions in HbA1c levels were similar in the TRE and CR groups compared with the control
group. Participants in the TRE group found it easier to adhere to their intervention and achieved
greater overall energy restriction compared with the CR group. Medication effect score did not
change in any group, and no serious adverse events were reported.
Only 2 clinical trials7,8 to date have examined how TRE affects body weight in patients with T2D.
Che and colleagues8 demonstrated that 12 weeks of 10-hour TRE (without calorie counting) reduced
body weight by 3.5% compared with controls in 120 adults with obesity and T2D. Likewise,
Andriessen et al7 showed that 9-hour TRE produced 1.1% weight loss after 3 weeks compared with
controls among 14 men and women with obesity and T2D. The weight loss produced by our 8-hour
TRE intervention was slightly greater (4.3% from baseline) than that of previous reports,7,8 but this
was most likely due to the longer intervention period (6 months). In contrast, the weight loss by the
CR group was not significant relative to the control or TRE group. This is surprising, as CR generally
reduces body weight by 4% to 7% after 6 months in people with T2D.17-19 However, the participants
in the CR group in our trial reported more difficulty with adhering to their intervention, relative to
TRE. Since CR is commonly prescribed as a first-line intervention in T2D, it is likely that our
participants had already tried calorie counting in the past, without success. Time-restricted eating
may have served as a refreshing alternative to CR, in that it only required patients to count time
instead of calories, which may have bolstered overall adherence and weight loss in the TRE group.
Reductions in HbA1c levels were similar for participants in the TRE (−0.91%) and CR (−0.94%)
groups, relative to controls. Our findings for HbA1c levels are comparable to other TRE trials in T2D7,8
and the Look AHEAD (Action for Health in Diabetes) study, which implemented daily CR.20 The
improvements in HbA1c levels by CR are somewhat unexpected, since only the TRE group lost weight
relative to controls. However, both TRE and CR led to comparable reductions in waist circumference
(a surrogate marker of visceral fat mass). Evidence suggests that visceral fat mass may be a stronger
factor associated with changes in glycemic control than body weight alone.21,22 Moreover, both the
TRE and CR groups received individualized diabetes nutrition counseling, which has been shown

Table 3. Dietary Intake and Physical Activity
Participant group, mean (SD)a
TRE

CR

Control

Variable

Baseline

6 mo

Baseline

6 mo

Baseline

6 mo

Daily eating window

11 h 55 min
(1 h 37 min)

8 h 3 min
(1 h 54 min)b

10 h 29 min
(1 h 36 min)

10 h 23 min
(1 h 35 min)

10 h 23 min
(1 h 26 min)

10 h 21 min
(1 h 14 min)

Energy intake, kcal/d

1978 (582)

1665 (468)b

1707 (319)

1510 (358)b

1834 (354)

1818 (14)

Dietary intake
Protein, %

18 (4)

19 (4)

17 (4)

17 (6)

19 (4)

19 (4)

Carbohydrates, %

42 (7)

41 (7)

41 (5)

42 (8)

41 (9)

40 (9)

Total sugar, %

15 (5)

14 (6)

15 (4)

15 (7)

15 (6)

14 (4)

Fat, %

40 (4)

40 (5)

42 (3)

41 (9)

40 (5)

41 (7)

Saturated fat, %

13 (2)

13 (3)

13 (2)

12 (3)

13 (2)

12 (2)

Cholesterol, mg

363 (146)

302 (97)

329 (149)

306 (111)

352 (126)

308 (142)

Fiber, g

16 (6)

15 (6)

15 (6)

14 (6)

15 (4)

13 (4)

Sodium, mg/d

3602 (1233)

3402 (790)

3259 (866)

2927 (614)

3311 (1095)

3126 (1291)

Caffeine, mg/d

91 (66)

93 (107)

90 (78)

81 (93)

89 (99)

96 (99)

Alcohol, g/d

2 (4)

1 (1)

2 (3)

1 (2)

0 (1)

0 (1)

5568 (2908)

6049 (2625)

6142 (4885)

6025 (4701)

6051 (2623)

5512 (2545)

Physical activity, steps/d

Abbreviations: CR, calorie restriction; TRE, time-restricted eating.
a

Only observed values are included. A total of 20 of 25 participants in the TRE group, 20 of 25 in the CR group, and 19 of 25 in the control group returned all food recalls.

b

Significantly different from baseline (P < .05).
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significantly improve HbA1c levels.23,24 These factors may explain why similar improvements in HbA1c
levels were noted in the TRE and CR groups, even though only the TRE group lost weight relative to
controls.
Our findings also show that TRE is safe in patients who are using either diet alone or
medications to control their T2D. However, for people using sulfonylureas and/or insulin, adopting a
TRE regimen will require medication changes and regular monitoring, particularly in the initial stages
of the diet.
Hispanic and non-Hispanic Black adults are among the racial and ethnic groups with the highest
prevalence of T2D in the US.25 Our results show that TRE is effective for weight loss and HbA1c level
reductions in a sample population that was representative of these 2 groups. Time-restricted eating
is an appealing approach to weight loss in that it can be adopted at no cost, allows patients to
continue consuming familiar foods, and does not require complicated calorie counting. Since the
literature on TRE is still quite limited,26 our trial may help to improve the health of groups with a high
prevalence of T2D by filling in these critical knowledge gaps.

Limitations
Our study has some limitations, which include the relatively short trial duration and the lack of
blinding of participants. Moreover, a higher percentage of participants in the TRE group were using
sodium-glucose transport protein 2 inhibitors and glucagonlike peptide-1 receptor agonists at
baseline. These medications could have influenced our body weight findings,27 even though
participants had stable weight before enrollment. To control for these confounding variables, we
accounted for the use of these medications in the analyses of our primary and secondary outcomes.
In addition, we relied on self-reported dietary intake. Since individuals with obesity tend to
underreport energy consumption by 15% to 20%,28 it is likely that our estimates of energy intake are
inaccurate. Last, TRE itself can be associated with greater self-monitoring and lower caloric intake,
so although these effects were noted in the TRE group, these are expected as part of the
intervention.

Conclusion
This randomized clinical trial found that 8-hour TRE without calorie counting was an effective
alternative diet strategy for weight loss and lowering of HbA1c levels compared with daily calorie
counting in a sample of adults with T2D and obesity. These findings will need to be confirmed by
larger RCTs with longer follow-up.

ARTICLE INFORMATION
Accepted for Publication: September 9, 2023.
Published: October 27, 2023. doi:10.1001/jamanetworkopen.2023.39337
Open Access: This is an open access article distributed under the terms of the CC-BY-NC-ND License. © 2023
Pavlou V et al. JAMA Network Open.
Corresponding Author: Krista A. Varady, PhD, Department of Kinesiology and Nutrition, University of Illinois
Chicago, 1919 W Taylor St, Chicago, IL 60612 (varady@uic.edu).
Author Affiliations: Department of Kinesiology and Nutrition, University of Illinois Chicago (Pavlou, Cienfuegos,
Lin, Ezpeleta, Ready, Corapi, Wu, Lopez, Gabel, Tussing-Humphreys, Oddo, Varady); University of Illinois Cancer
Center, University of Illinois Chicago (Tussing-Humphreys, Varady); Department of Preventative Medicine
(Biostatistics), Northwestern University, Chicago, Illinois (Alexandria); College of Medicine (Endocrinology),
University of Illinois Chicago (Sanchez, Unterman); Department of Endocrinology, Jesse Brown Veterans Affairs
Medical Center, Chicago, Illinois (Unterman); Division of Diabetes, Endocrinology and Metabolism, Department of
Medicine, University of Minnesota, Minneapolis (Chow); Center for Endocrinology, Diabetes and Metabolism,
Department of Pediatrics, Children’s Hospital Los Angeles and Keck School of Medicine of the University of

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Southern California, Los Angeles (Vidmar).
Author Contributions: Dr Varady had full access to all of the data in the study and takes responsibility for the
integrity of the data and the accuracy of the data analysis.
Concept and design: Pavlou, Cienfuegos, Lin, Gabel, Unterman, Varady.
Acquisition, analysis, or interpretation of data: Pavlou, Cienfuegos, Ezpeleta, Ready, Corapi, Wu, Lopez, TussingHumphreys, Oddo, Alexandria, Sanchez, Unterman, Chow, Vidmar, Varady.
Drafting of the manuscript: Pavlou, Wu, Tussing-Humphreys, Vidmar, Varady.
Critical review of the manuscript for important intellectual content: Pavlou, Cienfuegos, Lin, Ezpeleta, Ready,
Corapi, Lopez, Gabel, Tussing-Humphreys, Oddo, Alexandria, Sanchez, Unterman, Chow, Vidmar, Varady.
Statistical analysis: Cienfuegos, Oddo, Alexandria, Vidmar.
Obtained funding: Varady.
Administrative, technical, or material support: Pavlou, Cienfuegos, Lin, Ready, Lopez, Sanchez, Unterman, Vidmar.
Supervision: Pavlou, Cienfuegos, Lin, Gabel, Varady.
Conflict of Interest Disclosures: Ms Ready reported being a member of the Certified Diabetes Care and Education
Specialist for the Academy of Nutrition and Dietetics and being employed as a clinician at Ascension Medical Group
Weight Loss Solutions and Diabetes Education outside the submitted work. Dr Chow reported receiving
nonfinancial support from DexCom Inc outside the submitted work. Dr Vidmar reported receiving consulting fees
from Rhythm Pharmaceuticals Inc, Hippo Technologies Inc, and Guidepoint Inc and grant funding from DexCom
Inc, outside the submitted work. Dr Varady reported receiving grant funding from the National Institute of
Diabetes and Digestive and Kidney Diseases (NIDDK) of the National Institutes of Health (NIH) during the conduct
of the study; receiving personal fees from the NIH for serving on the data and safety monitoring boards for the
Health, Aging and Later-Life Outcomes and Dial Health studies; receiving author fees from Pan MacMillan for The
Fastest Diet; and serving as the associate editor for nutrition reviews from Elsevier outside the submitted work. No
other disclosures were reported.
Funding/Support: This study was supported by the Department of Kinesiology and Nutrition, University of Illinois
Chicago, and by grants R01DK128180 and T32DK128782 from the NIDDK of the NIH (Dr Varady).
Role of the Funder/Sponsor: The funders had no role in the design and conduct of the study; collection,
management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and
decision to submit the manuscript for publication.
Data Sharing Statement: See Supplement 3.
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SUPPLEMENT 1.
Trial Protocol

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SUPPLEMENT 2.
eTable 1. Medication Use at Baseline and Month 6
eTable 2. Multiple Imputation Sensitivity Analysis Results
eTable 3. Adverse Events During the Intervention
eFigure 1. Experimental Design
eFigure 2. Adherence to the Diet Interventions
eFigure 3. Difficulty in Adhering to the Time-Restricted Eating vs Calorie Restriction Intervention
SUPPLEMENT 3.
Data Sharing Statement

JAMA Network Open. 2023;6(10):e2339337. doi:10.1001/jamanetworkopen.2023.39337 (Reprinted)

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