Which type of intermittent fasting is best for weight loss, according to science?

Recent research has shown that reducing calorie intake on three non-consecutive days a week is more effective for weight loss than daily calorie restriction. They claim this approach is easier to sustain over time.

                                                                        

A recent study published in the Annals of Internal Medicine showed that 4:3 intermittent fasting, which involves reducing calories over three non-consecutive days a week, may be more effective for weight loss than traditional daily calorie restriction diets.
According to the researchers, over the course of a year, study participants not only lost more weight, but also showed improvements in metabolic parameters such as blood pressure, cholesterol, and fasting glucose.

What the study on the scope of intermittent fasting consisted of.

The trial, conducted in Denver, Colorado, and led by Dr. Victoria Catenacci, an associate professor of medicine at the University of Colorado, randomly assigned 165 overweight or obese adults to two groups: one practicing 4:3 intermittent fasting and the other following a daily calorie restriction (DCR) diet.
The first group reduced their calorie intake by 80% for three non-consecutive days of the week, while on the remaining days they ate without restrictions, although with recommendations to choose healthy foods.
In the case of the second group, they were asked to reduce their daily calorie intake by 34% to achieve an equivalent weekly energy deficit.
 
And while the research does not specify the number of hours of fasting the first group engaged in, at the end of the year, the results showed that those who practiced intermittent fasting lost 7.6% of their body weight, while the daily calorie restriction group only achieved a 5% reduction.
 
The difference, although modestly significant, suggests that intermittent fasting may be a more effective strategy for those seeking sustainable weight loss.
Why it is better to fast for three days
Catenacci explained that the greater effectiveness of intermittent fasting could be due to the fact that this approach is easier to maintain over time.

“Counting calories can be cognitively taxing, and having to do it only three days a week may have made it easier to adhere to over time,” the researcher said in an interview with ABC News.
 
In addition to weight loss, participants in the intermittent fasting group also showed improvements in their metabolic health. The data revealed that this group experienced decreases in blood pressure, total cholesterol levels, and fasting glucose. The combination of weight loss with improvements in these key parameters is crucial for cardiovascular and metabolic health.
 
Behavioral support was key to success

One of the study's highlights was the comprehensive behavioral approach implemented to support participants. Both groups received support in the form of group meetings led by dietitians and personalized follow-up.

Dr. Danielle Ostendorf, co-author of the study and assistant professor at the University of Knoxville, emphasized the importance of this support: “This program really gave participants accountability and offered them social support. They were able to learn from each other,” she shared.

The behavioral component was essential to ensuring participants remained committed to the plan throughout the year, which partly explains the greater adherence to intermittent fasting compared to daily calorie restriction.         

Controversies and critical perspectives of the study

Despite the positive results, intermittent fasting is not without its critics. Some experts, such as Adam Collins, professor of nutrition at the University of Surrey, point out that the difference in weight loss between the groups is not as great as it might seem at first glance.

He argued that although participants in the intermittent fasting group showed more significant weight loss, data analysis suggests that the measurement of calorie intake may have underestimated actual intake, as only fasting days were recorded.

“It’s possible that participants who practiced intermittent fasting may have also eaten less on non-fasting days, although not consciously,” Collins opined. However, the 4:3 approach appears to have been more sustainable for participants, which may have helped maximize long-term benefits.

Medical recommendations on intermittent fasting

Intermittent fasting has gained popularity recently, but it's not suitable for everyone.

Nutritionist and diabetologist Marianela Aguirre Ackermann stated, "Intermittent fasting can be a useful tool for some overweight people, but it's not for everyone, and it should always be personalized and supervised by a healthcare professional."

Aguirre Ackermann emphasized that for sustainable and healthy results, any dietary approach must be tailored to individual needs.

 Regarding the duration of adherence to fasting, the expert recommends a flexible approach. "Some people can maintain it long-term, not necessarily every day," she noted. She also emphasized that unnecessary sacrifices should not be made that could lead to nutritional deficiencies or affect one's relationship with food.

 Is intermittent fasting a long-term solution?

The Annals of Internal Medicine study provides significant evidence in support of 4:3 intermittent fasting as an effective weight loss strategy, particularly given its long-term sustainability.

However, as Catenacci emphasizes, “the best diet for any person is one they feel they can maintain over time.” This reflects the importance of personalization and consultation with healthcare professionals before embarking on any significant dietary change.

Although intermittent fasting shows promise, it is not a magic bullet. It is crucial to approach weight loss in an individualized and mindful manner, with a balanced approach that considers each person's specific needs and goals. Ultimately, the success of any dietary approach depends on the ability to maintain it sustainably and healthily over the long term.