# Comparative effectiveness of morning and evening aerobic exercise on weight loss and physical fitness in Chinese college students with overweight and obesity

## TL;DR

Morning aerobic exercise is more effective than evening exercise for weight loss and improving body shape in overweight and obese Chinese college students.

## Contribution

This study demonstrates that morning exercise leads to greater reductions in waist circumference and skinfold thickness compared to evening exercise.

## Key findings

- Morning exercise significantly reduced minimum waist circumference, scapular skinfold thickness, and upper arm skinfold thickness.
- BMI was positively associated with vital capacity and negatively associated with physical fitness test performances.
- Morning exercise showed superior benefits for weight loss and body shape improvement compared to evening exercise.

## Abstract

Physiological and metabolic processes are influenced by biological rhythms. However, whether exercising in the morning or evening is more beneficial, given that these periods are two key time windows to incorporate exercise, has remained unclear. This study aimed to investigate the effects of morning versus evening exercise on weight loss, morphometric indicators, and physical fitness among Chinese college students with overweight and obesity.

A total of 31 students with overweight and obesity (18–22 years old) were randomly assigned to exercise in the morning (7 am to 10 am, n = 16) or evening (6 pm to 9 pm, n = 15). The morning exercise group had an average age of 19.69 ± 1.01 years and a body mass index (BMI) of 27.13 ± 2.66 kg/m². The evening group had an average age of 19.47 ± 0.99 years and a BMI of 27.91 ± 3.40 kg/m². In the morning group, 87.5% of participants were male, while 73.3% were male in the evening group. The intervention was aerobic running exercise for 60 min, five times a week for 10 weeks. Measurements were taken before and after the 10-week intervention.

The BMI values of male and female college students were significantly and positively associated with vital capacity (p < 0.001) and significantly and negatively associated with vital capacity weight index, 50-meter, 800-/1,000-meter, standing long jump, and chin-ups and sit-ups test performances (p < 0.001). Participants who trained in the morning showed significant reductions in minimum waist circumference (MWC) (p = 0.043, d = 0.77), scapular skinfold thickness (ST) (p = 0.002, d = 1.30) and upper arm ST (p = 0.006, d = 1.05) compared with those who trained in the evening.

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 living with overweight and obesity.

Chinese Clinical Trial Registry ChiCTR2400089594. Date of registration 11/09/2024.

The online version contains supplementary material available at 10.1186/s13102-025-01149-8.