Intermittent fasting (IF) is an eating pattern that alternates between periods of food intake and periods of fasting.

It is not a diet, because instead of focusing on what you eat, this approach emphasizes when you eat. Although the quality and nutritional value of the foods consumed at mealtimes remains crucial.

Among the most popular forms of intermittent fasting are:

Why is intermittent fasting recommended?

According to specialists and based on available evidence, intermittent fasting can be used in certain circumstances, always under professional supervision.

Below are some situations in which it is advisable to apply AI:

Weight loss: the Mayo Clinic states that “scheduled eating can cause cells to focus on repair, energy use, and balancing functions throughout the body. Research shows that intermittent fasting can improve some short-term signs of health, such as weight.”

A study published by the journal Obesity in 2022 concluded that intermittent fasting, in its various forms, can be an effective strategy for weight loss in overweight or obese adults, although they emphasize that results may vary depending on the fasting protocol and individual adherence.

Improve insulin sensitivity: The Spanish Society of Health and Integrative Medicine (SESMI) has noted that intermittent fasting “lowers glucose… and improves insulin sensitivity,” protecting the body against metabolic syndrome and associated disorders such as type II diabetes mellitus.

Research published by Cell Metabolism in 2018 found that time-restricted feeding (TRF), a form of intermittent fasting where the eating window is limited to the early hours of the day, improved insulin sensitivity and pancreatic beta cell responsiveness in men with prediabetes.

However,Once this disease is diagnosed, the situation is very different. The American Diabetes Association “emphasizes that people with diabetes who are considering intermittent fasting should consult their physician and a registered dietitian for careful management of their medications and glucose monitoring.”

Reduce markers of inflammation: Johns Hopkins Medicine acknowledges that research suggests that “intermittent fasting may help reduce inflammation, a key factor in many chronic diseases,” and that it may improve blood cholesterol levels and blood pressure.

Intermittent fasting is not for everyone

It is crucial to understand that intermittent fasting may be contraindicated in certain cases—especially in groups for whom reducing their calorie intake may be detrimental.

Among the group of people who should avoid intermittent fasting, or at least consult a health professional before considering it, are:

Pregnant or breastfeeding women: Nutrition experts strongly advise against intermittent fasting for pregnant or breastfeeding women.

“When you're breastfeeding, your body needs more calories than normal because those calories go to providing nutrients to your baby. When you're low on calories due to fasting, your milk supply and energy level can be affected,” explains Julia Zumpano, a dietitian cited by the Cleveland Clinic.

Children and adolescents: Nutrition specialists emphasize that children and adolescents are in a critical phase of growth and development, so their bodies require a constant and adequate supply of calories, proteins, vitamins, and minerals.

Along the same lines, the National Institutes of Health in the United States recommends that people under 25 years of age act with caution and consult a health professional before trying intermittent fasting.

People with eating disorders (past or present): The National Eating Disorders Association (NEDA) categorically advises against intermittent fasting in these cases, indicating that "restriction can be a trigger for binge eating and other disordered behaviors."

People who are underweight or malnourished. Intermittent fasting is contraindicated for those who are underweight or nutritionally fragile, as this practice could cause “loss of lean muscle mass due to atrophy” and other problems, according to an article in Arch Latinoam Nutr (2023).

High-performance athletes or people with very intense training:The International Society of Sports Nutrition (ISSN) recommends caution and professional advice for athletes considering IF, noting that “nutrient timing and total caloric intake are vital for performance and recovery, and intermittent fasting may not be compatible with all training demands.”