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New food fads are not always healthy in the long run. Intermittent fasting is in the news these days. This time-limited diet consists of alternating periods of fasting and periods of normal eating. Researchers recently showed that obese people restricting food intake between 7 am and 3 pm, combined with calorie restriction, can lose more than 7 kg in 14 weeks – compared to 3.9 kg for those who had only calorie restriction. .
Intermittent fasting involves cyclic periods of eating and fasting, typically 14 to 48 hours at a time. In animals, intermittent fasting has a wide range of benefits: it reduces body weight and/or body fat, improves insulin sensitivity, lowers glucose levels, lowers blood pressure, improves cardiovascular health, slows down cellular aging, slows down the progression of cancer, improves cognitive function. . , slows down the progression of neurodegenerative diseases and even increases life expectancy.
The human body has an internal clock, and many aspects of metabolism function optimally in the morning. Thus, eating in accordance with the body’s circadian clock (early in the day) can have a positive impact on health.
Among the various types of intermittent fasting, daily intermittent fasting, now known as time-restricted fasting (TRE), has become popular. In humans, we define TRE as eating for 10 hours or less per day and fasting for the remaining 14 hours of the day.
Animal studies show that TRE can prevent and reverse diet-induced obesity, as well as improve several cardio-metabolic parameters, including glucose tolerance, cholesterol levels, and blood pressure. Several highly controlled efficacy studies in humans report that TRE improves cardiometabolic parameters such as insulin sensitivity, blood pressure, and oxidative stress, even when calorie intake is the same as that of the study group.
Recently, a group of international researchers demonstrated the effectiveness of the method by determining the consumption time zone from 7:00 to 15:00. Study author Courtney M. Peterson of the University of Alabama at Birmingham and her colleagues noted that TRE can be done an average of 6 days a week and can lead to a significant improvement in mood. Their work has been published in the journal Obesity (Silver Spring).
An old study
Back in 2014, Courtney M. Peterson’s team received funding to study the impact of this diet. This first human test follows rodent studies showing that TRF reduces body fat and reduces the risk of chronic disease in rodents.
In a human study, Peterson and colleagues followed 11 overweight men and women on the one hand for four days of eating from 8:00 am to 2:00 pm, and on the other hand, for four days from 8:00 am until 20:00. The researchers tested the effect of TRE on calories burned and appetite. Participants tried both nutrition programs, consumed the same amount of calories both times, and completed all tests under supervision.
According to the researchers, TRE does not affect participants’ total calories burned, but it reduces snacking and increases fat burning for several hours at night. It also improves metabolic flexibility, which is the body’s ability to switch between burning carbohydrates and burning fat.
Benefits in addition to weight loss
Based on this finding, in the present study, to determine the effectiveness of TRE for weight loss and cardio-metabolic health, the researchers conducted a 14-week study between August 2018 and April 2020. a body mass index (BMI) greater than or equal to 30 and did not have diabetes or a serious or unstable chronic disease.
They randomly assigned 90 participants to either a TRE with an 8-hour eating window from 7:00 am to 3:00 pm, or a 12-hour or longer time window designed to mimic typical eating habits in the United States (control group). group). All received treatment for weight loss with calorie restriction.
The authors noted that both study groups achieved clinically significant weight loss (-6.3 kg versus -4.0 kg), but RT plus calorie restriction were more effective for weight loss with an additional 2.3 kg loss.
However, the researchers noted that there were no statistically significant differences in absolute fat loss or the ratio of fat loss to weight loss. The authors noted a more pronounced improvement in cardiometabolic factors in the TRE group. In addition, based on questionnaires completed before and after the trial, intermittent eaters also reported greater improvement in their mood and less anger compared to the control group.
Cardiometabolic risk factors between the TRE group and the control group. © K.M. Peterson et al., 2022
Finally, the intermittent fasting group reported sleeping an average of 30 minutes less per day than the control group, but, paradoxically, felt less tired. The authors believe that this may be due to the body’s adaptation: having more time to rest without the process of digestion, it does this during the day while we are awake, which de facto causes a decrease in the need for sleep at night. Another explanation could be that the participants went to bed later and/or got up earlier to prepare meals for the day.
Future studies should use objective sleep measurements, such as actigraphy or polysomnography, to determine whether observed sleep changes are healthy or not in the long term.
An incomplete study that casts doubt
The authors were unable to trace this benefit in weight loss through changes in appetite, food restrictions, physical activity, or food intake. The authors acknowledge several biases such as sample size (moderate), participants who are predominantly female, and self-reported measures of sleep and physical activity (so they are highly subjective).
Dr Simon Stinson, a nutritionist at the British Nutrition Foundation who was not involved in the study, said in a statement: “One of the strengths of this new study is the study design and the number of participants compared to many previous trials. on a date. However, another study published in April this year of 139 people in China found that there was no significant difference between those on ERT or on a permanent energy restriction diet after a longer period of 12 months. .
He adds that the discrepancy between the latest and current trial is similar to the discrepancy between previous time-limited feeding trials, and emphasizes the need for larger studies to provide stronger evidence for clinical benefits. health in overweight and obese people, as well as additional studies on the effect on sleep.
In conclusion, obese adults who practice TRE for at least 5 days per week lose more weight and body fat and show greater improvements in cardio-metabolic health and mood than those who eat regularly for more than 12 hours.