Intermittent fasting: what a new study says about its effect on weight loss

Many modalities are implemented with the goal of losing weight. And even within the same pattern, there are many ways to carry them out. This is what happens with intermittent fasting. A new study focused on the method that leads to eating without caloric restriction but over a limited period of time. The result? "Moderate" weight loss. This is the conclusion reached regarding intermittent fasting in adults with prediabetes, obesity, or type 2 diabetes controlled by diet. The study, funded by the National Institutes of Health and the American Heart Association, and published in the journal Obesity, presents the most recent findings of an ongoing investigation led by Daisy Duan, an endocrinologist at Johns Hopkins Medicine, on how time-restricted eating (but without caloric restriction) can change body weight and other functions. Intermittent Fasting There is no single way to practice intermittent fasting. This is how the three most common modalities are implemented: - Alternate-day fasting: alternating a day where food is consumed normally with a fasting day where 500 calories are consumed in a meal. - The 5:2 Diet: a modified version of alternate-day fasting that includes five days of regular intake and two fasting days per week. - Time-restricted eating: limiting food intake to a specific number of hours, generally from 4 to 10 hours daily, without caloric restrictions during the eating period. This last one is the basis for the study. Cardiometabolic Complications Obesity and prediabetes carry a greater risk of suffering cardiometabolic complications, such as hypertension, heart attack, and stroke, and it is predicted that the figures for those who suffer from them will increase. Subscribe to Buena Vida Every fifteen days, Florencia Cunzolo tells you the latest to take care of your health and feel good. Register here. Intermittent fasting, a general term that encompasses structured patterns of fasting and eating that focus on modifying meal schedules rather than reducing calories or avoiding certain foods, has been widely associated with weight loss and can benefit people with one or both conditions. In order to expand clinical knowledge about time-based dietary interventions, Duan's team investigated whether the health benefits linked to intermittent fasting and other time-based dietary plans are solely due to weight loss or if other biological mechanisms are also involved. The Study The study was based on time-restricted eating (TRE), a form of intermittent fasting that consists of eating only during a constant daily period of 8 to 10 hours. Unlike other studies on time-restricted eating, this one focused on determining whether restricting meal schedules, while maintaining a constant caloric intake, would modify other factors related to obesity, such as eating behavior, inflammation, and the hormones that regulate appetite. In the 12-week study, a cohort of adults aged 18 to 69 years, predominantly female (92%) with obesity and prediabetes or type 2 diabetes controlled by diet were randomly assigned to a time-restricted eating (TRE) program of 10 hours, or a habitual eating pattern of 16 hours. All study participants received the same adapted diet from the Approaches to Stop Hypertension (DASH), a heart-healthy diet that emphasizes limiting the consumption of red meats, fatty foods, sugar, and salt. Caloric intake was personalized to maintain their initial weight, and all meals were prepared and provided by the ProHealth Clinical Research Unit at Johns Hopkins in Baltimore, Maryland, under the supervision of dietitians. Before and after the study, participants provided fasting blood samples to measure markers of inflammation and appetite hormone levels. Furthermore, they completed a Three-Factor Food Questionnaire, a tool that evaluates how a person interacts with food and how they think about it. The researchers used both instruments to record and compare the physical and psychological changes over time. Upon concluding the study, the researchers observed similar and moderate weight loss in both the group that followed time-restricted eating (median of 2.7%) and the group that followed the habitual eating pattern (median of 2.5%). Participants from both groups reported greater self-control in relation to food, less tendency to eat under stress, and lower general hunger. However, appetite hormones (ghrelin and leptin) and inflammation markers (C-reactive protein, cortisol, and sRAGE) were comparable between participants in both groups. "We observed that people who followed a 10-hour time-restricted eating schedule lost weight and positively modified their eating habits without restricting calories," Duan admitted. "But we did not identify any overall health benefits linked to this dietary strategy beyond that," she countered. Intermittent Fasting vs. Traditional Diet In line with this study, another article published a few years ago in the journal Annual Review of Nutrition based on the evidence review from more than 25 studies involving the three types of intermittent fasting, researchers from the University of Illinois in Chicago (UIC) pointed out that intermittent fasting can produce clinically significant weight loss and improve metabolic health in people with obesity. But, is it better than a traditional diet?, the researchers asked. "We noticed that intermittent fasting is not better than a regular diet; both produce the same amount of weight loss and similar changes in blood pressure, cholesterol, and inflammation," summarized Krista Varady, a nutrition professor at the College of Applied Health Sciences at UIC (United States) and author of the article Cardiometabolic Benefits of Intermittent Fasting. According to the evidence review conducted by her team, all the forms of fasting analyzed produced a slight to moderate weight loss, from 1% to 8% of initial weight, which represents results similar to those of more traditional and calorie-restricted diets. In the same vein, at the beginning of this year, a review was published by the Cochrane Iberoamerica Network, which analyzed the available evidence on the topic (up to November 2024). After analyzing 22 randomized clinical trials involving almost 2000 adults from various countries, their authors concluded that intermittent fasting for weight loss "does not live up to its fame." The researchers stated that it is unlikely that practicing intermittent fasting favors greater weight loss in adults with overweight or obesity compared to following traditional eating advice or doing nothing. Who Should Not Practice Intermittent Fasting Finally, it is important to note that there are several groups that should not do intermittent fasting, according to studies: ✔ Pregnant or breastfeeding women. ✔ Those under 12 years old. ✔ Those with a history of eating disorders. ✔ People with a body mass index (BMI) less than 18.5. ✔ Shift workers. Studies showed that they may have problems with fasting regimens due to changing work schedules. ✔ People who need to take medications with food at regulated times. *** Do you have any health and wellness questions you would like us to address in the section notes? Write your query to buenavida@clarin.com. Clarín Newsletter Receive all the news, stories, and analyses from Clarín journalists in your mail I WANT TO RECEIVE IT