# Effects of early vs. late time restricted eating vs. daily caloric restriction on weight loss and metabolic outcomes in adults with obesity

> **NIH NIH R01** · UNIVERSITY OF COLORADO DENVER · 2023 · $694,556

## Abstract

PROJECT SUMMARY
The goal of this proposal is to determine the optimal time restricted eating (TRE) window to produce weight loss
in adults with overweight or obesity. Daily caloric restriction (DCR), the current standard of care dietary strategy
for weight loss, produces 5-7% weight loss in the context of a guidelines-based behavioral weight loss program,
yet adherence is challenging and weight regain is common. Thus, rigorous evaluation of the effectiveness
of novel dietary interventions is needed to provide a range of evidence-based options to effectively treat
obesity. TRE involves restriction of energy intake (EI) to a limited window of time each day and has been widely
promoted in the lay press, but TRE studies to date have shown only minimal (0-4%) weight loss. However, prior
TRE studies have several substantial limitations, including lack of standard of care DCR control groups, small
sample sizes, short duration, and failure to provide appropriate obesity treatment guidelines-based behavioral
support. While several different dietary strategies can be used to achieve energy restriction, behavioral support
is critical to enhancing adherence to both diet and physical activity (PA) recommendations and thus weight loss
outcomes, yet no prior studies have provided behavioral support for TRE. Further, most TRE studies to date
have utilized late TRE windows (L-TRE, e.g., eating window 12-8 PM), often providing the rationale that
participants are more likely to adhere to L-TRE rather than early TRE (E-TRE, e.g. eating window 8AM-4PM).
However, there is strong rationale from mechanistic studies to suggest E-TRE may result in greater weight loss
and cardiometabolic benefits than L-TRE. We have shown that E-TRE results in improvements in glucose
variability and insulin sensitivity, clinically significant weight loss (6.3 ± 4.1% at 12 weeks), as well as
improvements in dietary quality, increased PA, reduced sedentary time and subjective improvements in
sleep. However, we did not include a L-TRE control, so it is unclear whether the E-TRE window or the provision
of behavioral support enhanced weight loss outcomes as compared to prior TRE studies. Thus, a rigorously
designed trial is needed to evaluate the impact of E-TRE, L-TRE and DCR delivered in the context of a
guidelines-based behavioral intervention on weight loss and cardiometabolic outcomes. In this study, 162 adults
with overweight or obesity will be randomized 1:1:1 to E-TRE (8-hr window starting 1-2 hrs after waking), L-TRE
(8-hr window starting 5-6 hrs after waking) or DCR (25% caloric restriction) for 26 weeks (primary outcome), with
follow up at 52 weeks. Our aims are to compare the effects of E-TRE, L-TRE, and DCR on: 1) Changes in body
weight and composition and markers of cardiometabolic health; 2) Dietary adherence, EI and dietary quality; and
3) PA and sleep. Our overall hypothesis is that E-TRE will result in greater weight loss and improvements in
cardiometabolic outcomes as compare...

## Key facts

- **NIH application ID:** 10585523
- **Project number:** 1R01DK132372-01A1
- **Recipient organization:** UNIVERSITY OF COLORADO DENVER
- **Principal Investigator:** Elizabeth Anne Thomas
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2023
- **Award amount:** $694,556
- **Award type:** 1
- **Project period:** 2023-04-05 → 2028-01-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10585523

## Citation

> US National Institutes of Health, RePORTER application 10585523, Effects of early vs. late time restricted eating vs. daily caloric restriction on weight loss and metabolic outcomes in adults with obesity (1R01DK132372-01A1). Retrieved via AI Analytics 2026-05-25 from https://api.ai-analytics.org/grant/nih/10585523. Licensed CC0.

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