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In a nutshell
Combining time-restricted eating with exercise led to approximately 1.3 kg (2.9 pounds) more fat loss compared to exercise alone, without compromising muscle mass
Most studies used a 16:8 schedule (16 hours fasting, 8 hours eating) with feeding windows between noon and 8 P.M., with exercise performed during feeding hours
The benefits of this approach were consistent across different exercise types (aerobic, resistance, or combined training) and participant characteristics
UNIVERSITY, Miss. — There’s promising news for fitness enthusiasts looking to optimize their body composition: combining a time-restricted eating (also known as intermittent fasting) regimen with your exercise routine may help reduce body fat while preserving muscle mass.
Researchers have discovered that coordinating when you eat with your exercise routine might significantly improve body composition results, according to a comprehensive study published in the International Journal of Obesity. The new meta-analysis by scientists at the University of Mississippi, along with colleagues from Texas Tech University, reveals an intriguing fitness strategy that doesn’t involve fancy equipment, expensive supplements, or complicated diet plans.
The secret to a truly fit body may be all about timing your meals and your workout in concert with one another.
The Power of Time-Restricted Eating with Exercise
Time-restricted eating (TRE) involves limiting all food consumption to a specific window—typically 4-12 hours daily—while fasting for the remaining hours. Unlike other dietary approaches that dictate specific foods or calorie counts, TRE focuses simply on when you eat.
The research team analyzed 15 studies involving 338 participants who followed TRE protocols while engaging in structured exercise programs. They compared these individuals to control groups who performed identical exercises but ate without time restrictions.
The results were clear: people who combined TRE with exercise lost approximately 1.3 kg (2.9 pounds) more fat and reduced their body fat percentage by an additional 1.3% compared to those who exercised without meal timing restrictions. Perhaps most importantly, muscle mass wasn’t significantly affected, indicating that TRE doesn’t compromise muscle preservation during exercise programs.
Intermittent fasting is already linked to many health benefits. Now researchers say that when it’s paired with an exercise routine, individuals should see greater fat-burning benefits. (Credit: MIA Studio/Shutterstock)
Most studies used a 16:8 schedule—16 hours fasting, 8 hours eating—with feeding windows typically between noon and 8 P.M. Importantly, exercise was performed during feeding hours, not while fasting, which likely helped preserve muscle mass and optimize performance.
“[T]ime-restricted eating appears to induce a small decrease in fat mass and body fat percentage while conserving fat-free mass in adults adhering to a structured exercise regimen, as opposed to exercise-matched controls without temporal eating restrictions,” the authors write.
Why This Combination Works
Several mechanisms might explain why restricting your eating window enhances fat loss beyond exercise alone.
For many people, TRE naturally reduces caloric intake by limiting opportunities to eat. However, benefits persisted even in studies that controlled for calories, indicating that timing itself matters regardless of how much you eat.
Eating during daylight hours may better align with our body’s natural biological rhythms—the internal clocks that regulate numerous physiological processes. This alignment could optimize metabolic function compared to the typical modern pattern of eating from early morning until late night.
TRE may also trigger beneficial hormonal changes, including increased levels of compounds that enhance fat burning (adiponectin, noradrenaline, growth hormone) while decreasing stress hormones like cortisol. Additionally, fasting periods activate metabolic pathways that promote fat oxidation, potentially amplifying exercise’s effects.
The research examined multiple exercise approaches, including aerobic training (running, cycling), resistance training (weightlifting), and concurrent training (combining both). The benefits held across these different exercise modes, indicating the TRE plus exercise formula works regardless of your preferred workout style.
When paired with exercise, time-restricted eating – eating only within a certain time period each day – can help healthy people lose fat without losing lean tissue, according to a University of Mississippi study. (Photo illustration by Stefanie Goodwiller/University Marketing and Communications)
What This Means for Your Fitness Routine
Before rushing to adopt this approach, however, several factors deserve consideration. The benefits, while statistically significant, were moderate in size. Individual responses likely vary considerably based on factors not fully captured in current research. And since most studies were short-term (typically 4-8 weeks), the long-term sustainability and effects remain largely unknown.
It’s also worth noting that most participants were already experienced exercisers in good metabolic health, with relatively few studies including those with obesity. Whether the same benefits apply to beginners or those with significant metabolic challenges remains unclear.
For active individuals looking to fine-tune their approach to body composition, this research provides preliminary support for a simple yet potentially effective strategy: timing meals alongside exercise may help optimize fat loss while preserving valuable muscle tissue.
As always before making any changes to your diet or daily health regimens, you should always talk to your doctor first.
Paper Summary
Methodology
The researchers conducted a systematic review and meta-analysis following established scientific guidelines. They searched five major research databases for relevant studies published between October 2016 and February 2023. From an initial pool of 1,005 articles, they narrowed the selection to 15 studies that met all inclusion criteria.
To qualify, studies needed to be randomized controlled trials or randomized crossover studies involving healthy adults who followed a TRE protocol while exercising. Each study required a control group that performed the same exercises but without time restrictions on eating. All studies measured body composition (fat mass, body fat percentage, or fat-free mass) before and after the intervention and lasted at least 4 weeks.
The researchers used statistical methods to calculate the overall effect of TRE plus exercise compared to exercise alone. They also conducted analyses to determine whether factors like BMI, exercise type, study duration, and energy intake influenced the results.
Key Results and Findings
The meta-analysis revealed that combining TRE with exercise led to greater reductions in fat mass and body fat percentage compared to exercise alone, without compromising muscle mass.
For fat mass, the effect size was -0.20 (95% CI = -0.28 to -0.13, p < 0.001), translating to approximately 1.3 kg (2.9 pounds) additional fat loss in the TRE plus exercise groups compared to control groups.
Body fat percentage showed a similar pattern, with an effect size of -0.23 (95% CI = -0.35 to -0.11, p < 0.001), equating to roughly a 1.3% greater reduction in body fat percentage.
No significant difference emerged in fat-free mass between TRE and control groups (p = 0.07), suggesting that TRE did not lead to muscle loss when combined with exercise.
When performing subgroup analyses, the researchers found that age, BMI, exercise type, study duration, and energy intake did not significantly explain variations in outcomes. This suggests the benefits of TRE with exercise may apply across different populations and exercise approaches.
Limitations of the Research
The researchers acknowledged several important limitations to their findings. Most studies were relatively short-term, typically lasting only 4-8 weeks, with just one study exceeding 12 weeks. This makes it difficult to draw conclusions about long-term effects.
All studies relied on self-reported dietary intake, which often underestimates actual food consumption. This makes it challenging to determine precisely how energy intake influenced the results.
The researchers observed significant heterogeneity across studies, suggesting many factors affecting individual responses to TRE plus exercise remain unidentified or understudied.
Different body composition measurement methods were used across studies, potentially introducing additional variability. These included bioelectrical impedance analysis, dual-energy x-ray absorptiometry, and 4-compartment models.
Most participants were metabolically healthy and experienced exercisers, with few studies including individuals with BMI ≥ 30 kg/m². This limits the generalizability of findings to broader populations, particularly those with obesity or metabolic disorders.
Discussion and Takeaways
The findings align with previous research showing that intermittent fasting approaches can reduce fat mass while preserving lean mass when combined with resistance training.
Several mechanisms might explain these benefits. TRE may naturally limit calorie intake by restricting eating opportunities. However, the benefits persisted regardless of energy intake levels, suggesting additional mechanisms.
Most studies used TRE protocols with feeding windows during daylight hours, potentially aligning eating patterns with natural circadian rhythms. This alignment may improve metabolic function, as eating patterns that conflict with circadian rhythms have been linked to obesity and metabolic disorders.
TRE may also trigger beneficial hormonal changes and activate metabolic pathways that enhance fat burning during fasting periods.
For practical application, the research suggests that active individuals may benefit from incorporating TRE alongside their exercise regimen. The most common protocol involved a 16:8 schedule (16 hours fasting, 8 hours eating) with feeding windows typically between noon and 8 PM. Importantly, exercise sessions were performed during the feeding window, which may have helped preserve muscle mass and optimize performance.
Publication Information
This systematic review and meta-analysis titled “Effects of time-restricted eating with exercise on body composition in adults: a systematic review and meta-analysis” was published in the International Journal of Obesity in January 2025. The authors were Harry M. Hays, Pouria Sefidmooye Azar, Minsoo Kang, Grant M. Tinsley, and Nadeeja N. Wijayatunga from the University of Mississippi and Texas Tech University.
The study was funded by the Dean’s Office of the School of Applied Sciences at the University of Mississippi and Startup Funds from the University of Mississippi. One author, Grant M. Tinsley, disclosed being an inventor on an international patent related to “Compositions and methods of use of beta-hydroxy beta-methylbutyrate (HMB) associated with intermittent fasting,” which represents a potential conflict of interest. The remaining authors reported no conflicts of interest.