Time Restricted Eating vs. Caloric Restriction for Obesity

(Time2Eat Trial)

Overseen By Emilee Mickaliger

Age: 18+

Sex: Any

Trial Phase: Academic

Sponsor: University of Colorado, Denver

Must not be taking: Weight loss, Antipsychotics

Disqualifiers: Pregnancy, Diabetes, Cancer, CVD, others

No Placebo Group All trial participants will receive the active study treatment (no placebo)

Compensation: Varies

Number of Visits: Unknown

Duration: 52 weeks

162 Participants Needed

Trial Summary

What is the purpose of this trial?

The goal of this clinical trial is to learn about time restricted eating as a weight loss intervention in adults with obesity. The main questions it aims to answer are: 1. How does the timing of the eating window (early vs late time restricted eating) affect weight loss and changes in metabolic risk factors? 2. How does time restricted eating compare to standard of care (daily caloric restriction) for weight loss and changes in metabolic risk factors? Participants will be randomly assigned to either early time restricted eating, late time restricted eating, or daily caloric restriction. 1. They will be asked to follow the assigned dietary strategy for 1 year and will receive a group-based program for instruction and support. 2. They will be asked at several times during the year to have their weight and body composition measured, provide blood samples, track their food, and wear monitors for physical activity and sleep.

Will I have to stop taking my current medications?

The trial does not specify if you must stop taking your current medications, but it excludes those who have taken medications affecting weight or energy in the last 6 months. If your medication must be taken with food, it may depend on whether it can be adjusted to fit the eating schedule of the study.

What data supports the effectiveness of the treatment Time Restricted Eating vs. Caloric Restriction for Obesity?

Research shows that both time-restricted eating (TRE) and daily caloric restriction (CR) can lead to similar weight loss and improvements in body composition and cardiometabolic health in adults with overweight and obesity. Studies indicate that these methods are equally effective in reducing body weight and fat mass, regardless of the timing of food intake. ^{1 2 3 4 5}

Is time-restricted eating or caloric restriction safe for people with obesity?

Research suggests that time-restricted eating and caloric restriction are generally safe for people with obesity, as studies have shown no significant safety concerns. These methods have been explored for their effects on weight loss and metabolic health, but further research is needed to confirm long-term safety. ^{2 3 4 6 7}

How does the treatment of time-restricted eating and caloric restriction for obesity differ from other treatments?

This treatment is unique because it combines time-restricted eating (eating only during specific hours of the day) with caloric restriction (reducing daily calorie intake), which may help with weight loss and improve health markers without requiring a change in the types of food consumed. Unlike traditional continuous calorie restriction, this approach focuses on when you eat, potentially making it easier to follow and maintain. ^{1 4 8 9 10}

Eligibility Criteria

Adults aged 18-65 with obesity (BMI of 27-45 kg/m2) who typically eat over a span of more than 12 hours daily, own a smartphone, and can commit to the trial for one year without relocating. They must pass medical screenings and be willing to give informed consent.

Inclusion Criteria

My BMI is between 27 and 45.

Have a primary care physician (or are willing to establish care with a primary care physician prior to study enrollment) to address medical issues which may arise during screening or study procedures/interventions

Live or work within 45 minutes of the Anschutz Health & Wellness Center (exceptions may be made at the discretion of the Study PI on a case-by-case basis for highly motivated subjects)

Exclusion Criteria

Pregnancy or lactation for women (exceptions apply for specific postpartum conditions)

Weight loss >5kg in past 3 months for any reason except post-partum weight loss; weight gain >5kg in past 3 months requires assessment by PI

I have lost more than 50 lbs in the last 3 years, not due to childbirth.

Timeline

Screening

Participants are screened for eligibility to participate in the trial

2-4 weeks

Treatment

Participants follow assigned dietary strategy (early TRE, late TRE, or daily caloric restriction) for 1 year with group-based program for instruction and support

52 weeks

Several visits throughout the year for measurements and monitoring

Follow-up

Participants are monitored for safety and effectiveness after treatment

4 weeks

Treatment Details

Interventions

• DCR
• Early TRE
• Late TRE

Trial Overview The study is examining how early vs. late time restricted eating (TRE) impacts weight loss compared to daily caloric restriction (DCR). Participants will follow their assigned diet plan for a year with support from group-based programs.

Participant Groups

Group I: Late time restricted eating Experimental Treatment 1 Intervention

Participants will be asked to follow late time restricted eating

Group II: Early time restricted eating Experimental Treatment 1 Intervention

Participants will asked to follow early time restricted eating

Group III: Daily caloric restriction Active Control 1 Intervention

Participants will be instructed to follow daily caloric restriction

Who Is Running the Clinical Trial?

University of Colorado, Denver

Lead Sponsor

Trials

1,842

Recruited

3,028,000+

National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)

Collaborator

Trials

2,513

Recruited

4,366,000+

Findings from Research

Intermittent energy restriction (IER) strategies, such as intermittent fasting and time-restricted feeding, show similar effectiveness in weight loss compared to continuous energy restriction (CER) in adults with obesity, based on a review of randomized trials lasting at least 8 weeks.

Out of 11 studies analyzed, 9 found no significant differences in weight or body fat loss between IER and CER, suggesting that IER can be a viable alternative for obesity treatment.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Effectiveness of Intermittent Fasting and Time-Restricted Feeding Compared to Continuous Energy Restriction for Weight Loss. Rynders, CA., Thomas, EA., Zaman, A., et al.[2021]

In a study of 43 insulin-resistant adults over 12 months, both alternate-day fasting (ADF) and daily calorie restriction (CR) led to similar weight loss, with ADF resulting in an 8% reduction and CR a 6% reduction in body weight.

ADF was more effective than CR in significantly lowering fasting insulin levels and insulin resistance, with reductions of 52% and 53% respectively, compared to only 14% and 17% for CR, indicating ADF may be a better option for improving glucoregulatory factors in insulin-resistant individuals.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Differential Effects of Alternate-Day Fasting Versus Daily Calorie Restriction on Insulin Resistance. Gabel, K., Kroeger, CM., Trepanowski, JF., et al.[2020]

In a study of 81 participants over 39 weeks, early time-restricted eating combined with daily caloric restriction (E-TRE+DCR) did not lead to significantly greater weight loss compared to daily caloric restriction (DCR) alone, with both groups losing similar amounts of weight.

Both dietary strategies were equally acceptable to participants, showing similar adherence levels and no differences in body composition, dietary intake, or physical activity between the two groups.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Early time-restricted eating compared with daily caloric restriction: A randomized trial in adults with obesity. Thomas, EA., Zaman, A., Sloggett, KJ., et al.[2023]

In an 8-week study involving 37 adults with overweight and obesity, both early and delayed time-restricted eating (TRE) combined with caloric restriction (CR) led to significant weight loss and reductions in fat mass, with no significant differences between the two TRE timings.

All groups, including those only on caloric restriction, showed similar improvements in body composition and fasting glucose levels, suggesting that the timing of eating may not be as crucial as previously thought when combined with caloric restriction.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Cardiometabolic effects of early v. delayed time-restricted eating plus energetic restriction in adults with overweight and obesity: an exploratory randomised clinical trial. Queiroz, JDN., Macedo, RCO., Dos Santos, GC., et al.[2022]

Intermittent fasting (IF) may be an effective weight management strategy for overweight and obese adults, but its evidence base in humans is still limited, with only one published systematic review available.

Current guidelines from the National Institute for Health and Care Excellence (NICE) do not recommend very low calorie diets (VLCD) as a routine treatment for obesity, highlighting concerns about potential side effects and the sustainability of fasting approaches.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Intermittent fasting interventions for the treatment of overweight and obesity in adults aged 18 years and over: a systematic review protocol. Jane, L., Atkinson, G., Jaime, V., et al.[2022]

The ChronoFast trial will compare the effects of early time-restricted eating (eTRE) and late time-restricted eating (lTRE) on cardiometabolic health in 30 women with overweight or obesity over a 2-week period, focusing on insulin sensitivity and other health markers.

This study employs rigorous methods, including real-time dietary monitoring and continuous glucose tracking, to ensure compliance and assess the effectiveness of each eating pattern, aiming to provide clear recommendations for improving health outcomes.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Effects of Early vs. Late Time-Restricted Eating on Cardiometabolic Health, Inflammation, and Sleep in Overweight and Obese Women: A Study Protocol for the ChronoFast Trial. Peters, B., Koppold-Liebscher, DA., Schuppelius, B., et al.[2021]

Alternate-day fasting (ADF) is a safe and well-tolerated weight loss method, with 93% of participants completing the 8-week study without adverse effects.

While ADF and a standard caloric restriction diet produced similar weight loss results after 8 weeks, ADF showed more favorable changes in body composition, particularly in fat and lean mass, during the follow-up period.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

A randomized pilot study comparing zero-calorie alternate-day fasting to daily caloric restriction in adults with obesity. Catenacci, VA., Pan, Z., Ostendorf, D., et al.[2019]

In a 12-month study involving 58 low-income women with obesity, time-restricted feeding (TRF) did not lead to significant weight loss compared to a standard hypoenergetic diet, indicating that TRF may not be effective for weight reduction in this population.

However, TRF was associated with a reduction in body fat percentage and waist circumference, suggesting it may have some benefits for body composition, even if these changes are not clinically significant.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Effects of time-restricted feeding on body weight, body composition and vital signs in low-income women with obesity: A 12-month randomized clinical trial. de Oliveira Maranhão Pureza, IR., da Silva Junior, AE., Silva Praxedes, DR., et al.[2021]

In the CALERIE study, calorie restriction (CR) led to significant weight loss, explaining 41% of the variance in weight loss among participants, but the timing of meals also played a crucial role.

Shorter eating intervals and consistent timing for the first and last meals were associated with greater weight loss and enhanced adherence to CR, suggesting that optimizing meal timing could improve the effectiveness of CR protocols.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Associations between the timing of eating and weight-loss in calorically restricted healthy adults: Findings from the CALERIE study. Fleischer, JG., Das, SK., Bhapkar, M., et al.[2022]

This study is the first to evaluate the effects of time-restricted eating (TRE) on weight loss in a controlled manner, comparing it to a usual eating pattern (UEP) while ensuring both groups consumed the same number of calories and identical diets.

Participants aged 21-69 with prediabetes and obesity were monitored closely, allowing for a rigorous assessment of how meal timing impacts weight change without altering caloric intake.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Design and Implementation of a Time-Restricted Eating Intervention in a Randomized, Controlled Eating Study. White, K., Wu, B., Pilla, SJ., et al.[2023]

References

1. Switzerland pubmed.ncbi.nlm.nih.gov

Effectiveness of Intermittent Fasting and Time-Restricted Feeding Compared to Continuous Energy Restriction for Weight Loss. [2021]

2. United States pubmed.ncbi.nlm.nih.gov

Differential Effects of Alternate-Day Fasting Versus Daily Calorie Restriction on Insulin Resistance. [2020]

3. United States pubmed.ncbi.nlm.nih.gov

Early time-restricted eating compared with daily caloric restriction: A randomized trial in adults with obesity. [2023]

4. England pubmed.ncbi.nlm.nih.gov

Cardiometabolic effects of early v. delayed time-restricted eating plus energetic restriction in adults with overweight and obesity: an exploratory randomised clinical trial. [2022]

5. Australia pubmed.ncbi.nlm.nih.gov

Intermittent fasting interventions for the treatment of overweight and obesity in adults aged 18 years and over: a systematic review protocol. [2022]

6. Switzerland pubmed.ncbi.nlm.nih.gov

Effects of Early vs. Late Time-Restricted Eating on Cardiometabolic Health, Inflammation, and Sleep in Overweight and Obese Women: A Study Protocol for the ChronoFast Trial. [2021]

7. United States pubmed.ncbi.nlm.nih.gov

A randomized pilot study comparing zero-calorie alternate-day fasting to daily caloric restriction in adults with obesity. [2019]

8. England pubmed.ncbi.nlm.nih.gov

Effects of time-restricted feeding on body weight, body composition and vital signs in low-income women with obesity: A 12-month randomized clinical trial. [2021]

9. England pubmed.ncbi.nlm.nih.gov

Associations between the timing of eating and weight-loss in calorically restricted healthy adults: Findings from the CALERIE study. [2022]

10. Switzerland pubmed.ncbi.nlm.nih.gov

Design and Implementation of a Time-Restricted Eating Intervention in a Randomized, Controlled Eating Study. [2023]