A recent study led by the University of Granada (UGR), in collaboration with the Public University of Navarre and CIBER, has brought new evidence to light regarding the benefits of intermittent fasting. This increasingly popular strategy appears to be effective for weight loss, improving certain health markers, and—surprisingly—it does not negatively impact sleep quality, mood, or general well-being, regardless of the chosen eating schedule. But is it as promising as it seems?
An Effective and Well-Tolerated Strategy
The research, published in the prestigious journal Nature Medicine, involved nearly 200 participants aged 30 to 60 with overweight or obesity. They were divided into four groups: one receiving standard nutritional guidance and three practicing intermittent fasting with different eating windows—early (9:00 a.m. to 5:00 p.m.), late (2:00 p.m. to 10:00 p.m.), and self-selected (on average, 12:00 p.m. to 8:00 p.m.).
After 12 weeks of intervention, the results were clear: all intermittent fasting groups lost more weight—on average, 3 to 4 kilograms more—than those who only received conventional dietary recommendations. Furthermore, the strategy was well-tolerated, with no serious adverse effects reported and high adherence levels—typically one of the main challenges in any weight loss plan.
No Negative Impact on Sleep or Mood
One of the novel aspects of this study is that, beyond weight, it assessed key indicators such as sleep quality, stress, anxiety, depression, and quality of life. The findings are encouraging: intermittent fasting showed no negative effects in any of these areas, not even among women, who often report higher levels of emotional discomfort or sleep disorders.
Researchers used a combination of 14-day accelerometry and validated questionnaires to measure these parameters, adding robustness to the conclusions.
What Is TRE and Why Is It Gaining Ground?
The studied approach is known as Time-Restricted Eating (TRE), which involves limiting the number of hours during the day in which food is consumed. Compared to the typical Spanish pattern—between 12 and 14 hours of daily eating—TRE proposes reducing this window to just 8 hours.
This pattern not only supports a lower caloric intake but also better synchronizes the body’s circadian rhythms, helping to maintain a more stable hormonal and metabolic balance. Eating at irregular hours or late at night can disrupt melatonin production and other biological processes, negatively impacting sleep and overall well-being.
A More Sustainable Alternative Than Traditional Diets?
The authors of the study also emphasize a key point: long-term adherence. While many hypocaloric diets fail due to participants abandoning the program, intermittent fasting may prove to be a more sustainable strategy over time, as it focuses more on when you eat rather than what you eat.
But Is It All Good News?
Despite these encouraging results, not all scientific consensus supports intermittent fasting. Some recent research, such as that published by the American Heart Association, warns of potential risks when this practice is undertaken without medical supervision.
This particular study, based on data from more than 20,000 individuals, found that extending daily fasting to 16 hours may be associated with a significant increase in cardiovascular mortality. Similarly, experts like Dr. Giuseppe Russolillo, president of the Spanish Academy of Nutrition and Dietetics, have warned of the dangers of adopting such strategies as quick-fix or miracle weight loss solutions.
“If you use intermittent fasting to lose weight for 10 years without medical control, you will definitely increase your cardiovascular risk,” Russolillo recently cautioned.
The data from the UGR-led study is solid and promising. Time-Restricted Eating, as a form of intermittent fasting, appears to be an effective, safe, and well-tolerated tool for weight loss and improving general health, with no adverse effects on sleep or emotional well-being.
However, like any nutritional strategy, it is not suitable for everyone and should not be implemented without professional supervision. People with preexisting health conditions, eating disorders, or specific needs should consult their physician or registered dietitian before starting such a protocol.
Intermittent fasting is not a magic wand, but it can be a valuable ally—as long as it is integrated within a comprehensive healthy lifestyle, grounded in scientific evidence and guided by professional support.
