Intermittent fasting combined with exercise promotes weight loss in obese adults

A trial led by the Joint University Institute for Sport and Health shows benefits regarding weight, body fat, and cardiorespiratory fitness in people with obesity.

A research team led by the Joint University Institute for Sport and Health (iMUDS) at the University of Granada, in collaboration with the Granada Institute for Biomedical Research and the Biomedical Research Network Center, has studied the effects of combining intermittent fasting and supervised exercise in people with obesity as part of the TEMPUS project. The study, published in the prestigious journal Nature Communications, shows that combining intermittent fasting and supervised exercise promotes greater weight and body fat loss, in addition to improving cardiorespiratory fitness in people with obesity, although no greater reduction in accumulated liver fat was detected compared to standard care.

The trial included 187 obese adults, approximately half of whom were women. The participants were randomly assigned to four groups: standard care, intermittent fasting, supervised exercise, and fasting combined with exercise. For 12 weeks, all groups received education on the Mediterranean diet and physical activity. In addition, those who practiced intermittent fasting concentrated their meals within an eight-hour window each day. The exercise groups followed a supervised program that combined strength training and high-intensity aerobic exercise.

The primary objective was to determine whether these strategies led to a greater reduction in liver fat—measured by MRI—and an improvement in cardiovascular health. The results showed that liver fat decreased in all four groups. However, no statistically significant differences were found between the interventions and standard care, nor among the three interventions themselves.

Participants who fasted, with or without exercise, lost more weight than those who exercised only or received standard care. In both fasting groups, weight loss was, on average, about 2.2 kilograms greater than in the standard-care group. The combination of fasting and exercise also resulted in greater body fat loss than standard care and exercise alone. Meanwhile, the two groups that exercised improved their cardiorespiratory fitness, a marker of cardiovascular health.

These results allow us to assess the effects of the interventions beyond weight, also taking into account changes in liver fat deposits, as well as total body fat and physical fitness.”

Antonio Clavero Jimeno, co-lead author of the study and predoctoral researcher, University of Granada (UGR)

The study, which is part of Antonio Clavero Jimeno’s doctoral dissertation, also examined the response to the interventions in men and women. Among men, the combination of fasting and exercise produced a greater reduction in liver fat than standard care. This additional difference was not observed among women. Alba Camacho Cardeñosa, co-lead author of the study and a postdoctoral researcher at ibs.GRANADA, notes, however, that “for now, these analyses alone do not allow us to conclude that the intervention works differently depending on sex.”

Furthermore, among participants with fatty liver at the start of the study, approximately 30% of those who combined fasting and exercise no longer met the criteria used to diagnose this condition, compared to 6.5% in the standard-of-care group.

One year after completing the program, no differences were found between the groups in changes in liver fat. Furthermore, the differences in weight and body composition observed at the end of the 12 weeks were no longer detectable. These results suggest that it is necessary to analyze longer-term interventions, especially in people with high levels of liver fat, as well as strategies to help maintain the benefits.

This study was led by the PROFITH CTS-977 research group at the iMUDS of the University of Granada, in collaboration with the ibs. GRANADA, the San Cecilio University Clinical Hospital (HUCSC), and the Virgen de las Nieves University Hospital in Granada, together with the CIBER on Obesity (CIBEROBN) and the CIBER on Frailty and Healthy Aging (CIBERFES). The TEMPUS study (ref. PID2022-141506OB-I00) was funded by MICIU/AEI /10.13039/501100011033 and by the ERDF, EU.