What intermittent fasting is, how it works in the body, its potential benefits, and the risks of applying it incorrectly.
Intermittent fasting has become one of the most popular nutritional strategies in recent years, especially among individuals looking to lose weight. While it can offer metabolic and health benefits, it is not without risks if practiced without proper knowledge or supervision.
Adriana Martín Peral – Neolife Nutrition Unit
What Is Intermittent Fasting?
Intermittent fasting is not a diet per se, but rather an eating pattern that alternates periods of food intake with periods of fasting. It focuses less on what you eat and more on when you eat. Unlike traditional diets, it is not based on restricting specific foods, but on structuring the timing of meals.
Main Types of Intermittent Fasting
16:8 Fasting
This involves fasting for 16 hours and concentrating food intake within an 8-hour window. It is the most popular protocol due to its ease of integration into daily life.
14:10 Fasting
A more flexible version, recommended for beginners or individuals with higher energy demands.
5:2 Method
Five days of normal eating and two non-consecutive days with significantly reduced caloric intake.
Alternate-Day Fasting
Alternates days of normal eating with days of complete or partial fasting. It is more demanding and less sustainable for many people.
How Does Intermittent Fasting Work in the Body?
During the first hours of fasting, the body uses stored glucose in the form of glycogen. Once these reserves are depleted, it begins to rely on body fat as a source of energy.
This process is accompanied by:
- A decrease in insulin levels
- An increase in glucagon
- Activation of cellular repair mechanisms
These changes explain many of the effects associated with intermittent fasting.
Positive Effects of Intermittent Fasting
When properly implemented and adapted to the individual, intermittent fasting may offer several benefits:
1. Improved Insulin Sensitivity
Lower insulin levels promote better blood glucose control, which may be beneficial for individuals with insulin resistance or risk of type 2 diabetes.
2. Fat Loss
By promoting fat utilization as fuel, it may contribute to weight loss, especially when combined with a balanced diet.
3. Metabolic Health
Some studies associate intermittent fasting with improvements in markers such as cholesterol, triglycerides, and blood pressure.
4. Possible Activation of Autophagy
Fasting activates cellular recycling processes known as autophagy, which are linked to cellular health and longevity, although their impact in humans is still under investigation.
Negative Effects if Done Incorrectly
Intermittent fasting is not suitable for everyone, and improper implementation may lead to adverse effects:
1. Nutritional Deficiencies
Reducing eating windows without proper planning may result in insufficient intake of protein, vitamins, and minerals.
2. Digestive Issues and Fatigue
Skipping meals without prior adaptation can cause dizziness, weakness, constipation, headaches, or gastrointestinal discomfort.
3. Unhealthy Relationship with Food
In some individuals, it may promote disordered eating behaviors, binge eating, or a rigid relationship with food.
4. Not Recommended in Certain Cases
It is not advisable for:
- Pregnancy and breastfeeding
- Individuals with eating disorders
- Individuals with eating disorders
- People with certain medical conditions without professional supervision
Common Mistakes When Practicing Intermittent Fasting
- Overeating during the eating window
- Prioritizing ultra-processed foods
- Not meeting protein requirements
- Forcing excessively long fasting periods
- Ignoring the body’s signals
Recommendations for Safe Intermittent Fasting
- Start gradually (14:10 before 16:8)
- Prioritize fresh, nutrient-dense foods
- Maintain proper hydration
- Adapt fasting to lifestyle and activity level
- Consult a nutrition professional
Conclusion
Intermittent fasting can be a useful tool within a healthy eating approach, but it is not a universal solution. Its success depends on the individual, the context, and proper nutritional planning. When practiced with knowledge and supervision, it may provide benefits; when applied incorrectly, it can lead to more harm than good.
BIBLIOGRAPHY
(1) Mattson, M. P., Longo, V. D., & Harvie, M. (2017). Impact of intermittent fasting on health and disease processes. Ageing Research Reviews, 39, 46–58.
(2) Anton, S. D., et al. (2018). Flipping the metabolic switch: understanding and applying the health benefits of fasting. Obesity, 26(2), 254–268.
(3) Patterson, R. E., & Sears, D. D. (2017). Metabolic effects of intermittent fasting. Annual Review of Nutrition, 37, 371–393.
(4) Organización Mundial de la Salud (OMS). Healthy diet factsheet.