Morning vs Evening Exercise for Obesity

(TIMEX Trial)

Overseen By Kristen Bing

Age: 18 - 65

Sex: Any

Trial Phase: Academic

Sponsor: University of Colorado, Denver

Must not be taking: Appetite suppressants, Antipsychotics, Beta blockers, others

Disqualifiers: Diabetes, Hypertension, Depression, others

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

Compensation: Varies

Number of Visits: 3

128 Participants Needed

What You Need to Know Before You Apply

What is the purpose of this trial?

This trial aims to understand how exercising in the morning versus the evening affects weight, sleep, and eating habits. Researchers will assign participants to either morning or evening exercise sessions to determine which time might be more effective for weight management. Individuals who have struggled with obesity, are not currently very active, and live near the Anschutz Health & Wellness Center may be a good fit. The trial involves regular exercise and tracking health changes over time.

As an unphased trial, this study offers a unique opportunity to contribute to valuable research on exercise timing and its impact on health.

Will I have to stop taking my current medications?

The trial requires that you do not regularly use medications that significantly impact appetite, weight, sleep, or energy metabolism, such as appetite suppressants or certain antidepressants. If you are on such medications, you may need to stop taking them to participate.

What prior data suggests that these exercise routines are safe for participants?

Research shows that exercising in the morning or evening is generally safe for most people. Studies have found that working out at either time can improve body weight and fitness. Morning exercisers often have a lower risk of becoming overweight. Meanwhile, evening exercise can offer significant health benefits for those already overweight. No major reports have indicated harmful effects from exercising at either time. Overall, exercising in the morning or evening is safe and beneficial for health. ^{1 2 3 4 5}

Why are researchers excited about this trial?

Researchers are excited about the Morning vs Evening Exercise trial for obesity because it investigates how the timing of exercise can impact weight loss, a relatively unexplored area. Unlike current standard treatments for obesity, which often focus on diet, medication, or surgery, this trial examines lifestyle modification through exercise timing. By exploring whether morning or evening workouts are more effective, this study could lead to personalized exercise regimens that maximize fat loss and improve health outcomes. The potential for a non-invasive, cost-effective approach to managing obesity is what makes this investigation particularly appealing.

What evidence suggests that this trial's treatments could be effective for obesity?

This trial will compare the effects of morning exercise with evening exercise on obesity. Research has shown that morning exercise can be more effective for weight loss. One study found that people who worked out between 7 a.m. and 9 a.m. were less likely to be obese. Other studies have also linked morning exercise to lower body weight and smaller waist size. Participants in the morning exercise arm of this trial will engage in aerobic activities during these hours.

Exercising in the evening, however, offers its own benefits, particularly for overall health. Some research suggests that working out in the afternoon or evening can improve heart health and fitness, though it might not aid weight loss as much as morning exercise. Participants in the evening exercise arm of this trial will engage in aerobic activities during these later hours. Both morning and evening workouts benefit health, but the time of day can affect specific outcomes like weight loss or overall health improvements. ^{1 2 3 6 7}

Who Is on the Research Team?

Vicki Catenacci

Principal Investigator

University of Colorado, Denver

Are You a Good Fit for This Trial?

Adults aged 18-55 with a BMI of 25-40, physically inactive, without chronic diseases like CVD or diabetes. Participants must not be on certain medications, have no recent significant weight changes, and be willing to exercise in the morning or evening as assigned. They should live near the Anschutz Health & Wellness Center and commit to the study's duration.

Inclusion Criteria

I am not planning to get pregnant and use reliable birth control or have had a tubal ligation.

I own a smartphone and agree to use it for meal tracking and assessments.

I am willing and able to follow the study's requirements.

Exclusion Criteria

Night-time shiftwork, rotating work, irregular sleep/wake patterns or other scheduling constraints which may hinder ability to consistently exercise at specific times of the day

My heart's rhythm is irregular or I have a serious heart condition.

Current severe depression or history of severe depression within the previous year, based on Diagnostic and Statistical Manual of Mental Disorders (DSM-IV-TR) criteria for Major Depressive Episode. Score > 18 on Beck Depression Inventory (BDI) will require further assessment by the Study MD to determine if it is appropriate for the subject to participate in the study

Timeline for a Trial Participant

Screening

Participants are screened for eligibility to participate in the trial

2-4 weeks

Supervised Exercise

Participants engage in supervised aerobic exercise either in the morning or evening for weight loss

7 months

Regular supervised exercise sessions

Maintenance

Participants continue to exercise at the target of 2000 kcal/week during the randomized AM or PM exercise windows without supervision

6 months

Follow-up

Participants are monitored for changes in body weight, energy intake, and other factors

6 months

Assessments at 3.5, 7, and 13 months

What Are the Treatments Tested in This Trial?

Interventions

• Evening Exercise
• Morning Exercise

Trial Overview The trial is testing whether exercising in the morning versus evening has different effects on weight loss, sleep quality, eating habits, and other health aspects. Participants will be randomly assigned to one of two groups: those who exercise in the morning and those who exercise in the evening.

How Is the Trial Designed?

Group I: Morning Exercise (AM) Experimental Treatment 1 Intervention

Participants in this group will be prescribed morning aerobic exercise.

Group II: Evening Exercise (PM) Experimental Treatment 1 Intervention

Participants in this group will be prescribed evening aerobic exercise.

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+

Published Research Related to This Trial

The study successfully randomized 33 adults with overweight and obesity to either morning or evening aerobic exercise, achieving a high retention rate of 94% and adherence of over 90% to the exercise program.

Both morning and evening exercise groups showed changes in total daily energy expenditure (TDEE), with the morning group increasing TDEE more significantly, suggesting that the timing of exercise may influence energy balance and weight management, warranting further investigation.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Effect of Morning and Evening Exercise on Energy Balance: A Pilot Study. Creasy, SA., Wayland, L., Panter, SL., et al.[2022]

A systematic review and meta-analysis of 11 studies found that exercising in the morning or evening does not significantly affect systolic or diastolic blood pressure in adults.

Similarly, the timing of exercise (morning vs. evening) showed no significant impact on blood glucose levels, indicating that the time of day may not be a crucial factor for these cardiovascular risk factors.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Time of the day of exercise impact on cardiovascular disease risk factors in adults: a systematic review and meta-analysis. Sevilla-Lorente, R., Carneiro-Barrera, A., Molina-Garcia, P., et al.[2023]

In a study of 100 inactive adults with overweight or obesity, both morning and evening exercise led to significant weight loss after 12 weeks, with the morning group losing an average of 2.7 kg and the evening group losing 3.1 kg.

Both exercise groups showed improvements in cardiorespiratory fitness, but there was no significant difference in weight loss or fitness gains between morning and evening exercisers, suggesting that the timing of exercise does not impact overall effectiveness.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

The efficacy of morning versus evening exercise for weight loss: A randomized controlled trial. Brooker, PG., Gomersall, SR., King, NA., et al.[2023]

A 12-week study involving 100 adults with overweight or obesity showed that both morning and evening exercise significantly increased daily physical activity by about 12-22 minutes compared to baseline.

Participants in both exercise groups also reported improvements in their daily routines, including more sleep (up to 36 minutes) and less time spent on sedentary activities like watching TV or playing video games.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

How do previously inactive individuals restructure their time to 'fit in' morning or evening exercise: a randomized controlled trial. Brooker, PG., Gomersall, SR., King, NA., et al.[2023]

A 12-week moderate exercise training program improved physical fitness, body composition, and subjective sleep quality in overweight and obese adults, regardless of whether the exercise was done in the morning or evening.

While both morning and evening exercise led to similar overall benefits, morning workouts advanced sleep timing, while evening workouts delayed it, suggesting flexibility in scheduling exercise without compromising health outcomes.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Effect of morning versus evening exercise training on sleep, physical activity, fitness, fatigue and quality of life in overweight and obese adults. Saidi, O., Colin, E., Rance, M., et al.[2021]

In a study involving 50 overweight women, exercising in the morning resulted in significantly higher levels of satiety compared to exercising in the afternoon, suggesting that morning workouts may help control hunger better.

Overall, the timing of moderate-intensity exercise did not significantly affect appetite or energy intake patterns over the following 24 hours, indicating that the benefits of exercise on weight management may not depend on when it is performed.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Acute Effect of Morning and Afternoon Aerobic Exercise on Appetite of Overweight Women. Alizadeh, Z., Mostafaee, M., Mazaheri, R., et al.[2020]

In a study involving 16 healthy participants, evening exercise led to a significantly higher post-exercise energy intake (152 kcal more) compared to morning exercise, despite similar subjective appetite levels before and after workouts.

Morning exercise resulted in greater resting energy expenditure and carbohydrate oxidation, suggesting that while exercise timing affects energy balance, it does not impact immediate exercise performance.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Effects of Morning Vs. Evening exercise on appetite, energy intake, performance and metabolism, in lean males and females. Mode, WJA., Slater, T., Pinkney, MG., et al.[2023]

Exercise is a popular strategy for weight loss among adults, but its effectiveness can vary, potentially influenced by the time of day it is performed, with some studies suggesting morning exercise may lead to better weight and fat loss, while others indicate evening exercise could be more effective.

Understanding the impact of exercise timing on weight management could help tailor personalized treatment plans, as it may affect related behaviors like physical activity levels, energy intake, and sleep patterns.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Examining the Role of Exercise Timing in Weight Management: A Review. Blankenship, JM., Rosenberg, RC., Rynders, CA., et al.[2022]

Citations

1. pmc.ncbi.nlm.nih.gov pmc.ncbi.nlm.nih.gov/articles/PMC10108225/

The efficacy of morning versus evening exercise for weight ... The aim of this study was to investigate the influence of morning versus evening exercise on weight loss, cardiometabolic health, and components of energy ...

2. pubmed.ncbi.nlm.nih.gov pubmed.ncbi.nlm.nih.gov/36502286/

The efficacy of morning versus evening exercise for weight ... Conclusions: Adults with overweight and obesity experience modest weight loss in response to an exercise program, but there does not appear to ...

3. sciencedirect.com sciencedirect.com/science/article/pii/S2451865418301625

The feasibility and acceptability of morning versus evening ... Both intervention groups displayed improvements to their cardiometabolic risk profile; cardiorespiratory fitness improved by 5.2 ± 4.7, and 4.6 ± 4.5 mL kg−1.

4. nature.com nature.com/articles/s41366-025-01721-9

Diurnal timing of physical activity in relation to obesity and ... Afternoon and evening activity provide greater metabolic health benefits than morning activity, while nighttime activity is discouraged.

5. bmcsportsscimedrehabil.biomedcentral.com bmcsportsscimedrehabil.biomedcentral.com/articles/10.1186/s13102-025-01149-8

Comparative effectiveness of morning and evening aerobic ... Exercise in the morning, compared with that in the evening, has superior beneficial effects on weight loss and improving body shape in Chinese college students.

6. sydney.edu.au sydney.edu.au/news-opinion/news/2024/04/10/does-the-time-of-day-you-move-your-body-make-a-difference-to-you.html

Does the time of day you move your body make a ... Undertaking the majority of daily physical activity in the evening is linked to the greatest health benefits for people living with obesity.

7. pmc.ncbi.nlm.nih.gov pmc.ncbi.nlm.nih.gov/articles/PMC8591839/

Examining the Role of Exercise Timing in Weight Management Both morning exercise and evening exercise resulted in favorable changes in BMI and percent body fat compared to control. Because of the limited sample size, ...