A recent meta-analysis has sparked interest in the potential benefits of combining intermittent fasting with exercise for weight loss. This study, which synthesizes data from 15 separate studies, suggests that this combination could be a promising strategy for managing body weight. The research encompassed trials of varying lengths, with six studies spanning four weeks, seven lasting eight weeks, and one extending beyond 12 weeks.
The analysis primarily focused on a type of intermittent fasting known as time-restricted eating. In these studies, participants were generally allowed to consume food during a mid-day eating window, typically between noon and 9 p.m. This flexible approach to meal timing was accompanied by various forms of exercise, including aerobic, resistance, or a combination of both. Despite the diversity in study designs and participant demographics, the results consistently indicated that intermittent fasting paired with exercise could lead to reductions in body fat percentage and fat mass.
However, the studies were not without limitations. Thirteen of the studies involved participants with body mass indexes (BMIs) of 25 or less, which raises questions about the applicability of the findings to individuals with higher BMIs. Despite this, the researchers concluded that factors such as BMI, exercise type, age, energy intake, and study duration did not significantly impact the outcomes. The average age of participants was approximately 29 years old, and all were healthy adults without cardiometabolic conditions.
“You’d think that the average BMI [of the participants] would be in the overweight to obese category,” noted Kalyn True, RDN, LD.
The majority of the studies were conducted in the United States, with nine featuring exclusively male participants. This demographic detail emphasizes the need for more diverse research samples in future studies. The researchers acknowledged that their data collection methods and inclusion and exclusion criteria might have constrained their findings.
“While [time-restricted eating] with exercise could complement weight management strategies, its application must be individualized,” remarked Ryan Glatt, CPT, NBC-HWC.
Despite the potential for weight loss, the evidence remains inconclusive regarding whether time-restricted eating offers advantages over traditional calorie control paired with regular exercise routines. The meta-analysis estimated a possible reduction of 1.3% in body fat percentage and a decrease of 1.3 kg in fat mass. Yet, experts caution against jumping to conclusions without further evidence.
“Evidence remains inconclusive about whether [time-restricted eating] offers advantages over traditional calorie control and regular exercise routines. More rigorous, controlled trials are needed to confirm the effectiveness of [time-restricted eating] with exercise, particularly in diverse populations. Studies should also examine long-term adherence and real-world feasibility, as these factors heavily influence outcomes in practical settings,” emphasized Ryan Glatt.
The studies included were either randomized crossover studies or randomized controlled trials lasting at least four weeks. The researchers highlighted that it typically takes at least 12 weeks to observe significant body composition changes, underscoring the necessity for longer-term studies.
“Typically, it will take at least 12 weeks to see proper body composition changes regardless of time-restricted eating,” stated Kalyn True.
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