Intermittent Fasting, how to do it correctly?
What is intermittent fasting?
Intermittent fasting (IF) is a dietary pattern that involves alternating regular periods of unrestricted eating with prolonged periods of fasting. It is important to note that due to caloric restriction, it is recommended that this type of diet be implemented and monitored by a medical specialist. The mechanisms by which intermittent fasting produces not only weight reduction but also metabolic benefits are:
- Regulating enzymes involved in ketogenesis and fatty acid oxidation, and thus efficiently utilizing them as a source of energy.
- Reducing caloric intake leading to an energy deficit, which results in weight and fat mass loss over time.
- Improving insulin sensitivity, reducing inflammation, and promoting cellular repair.
Benefits of intermittent fasting
There is extensive clinical data on the benefits of intermittent fasting on health indicators. Let's take a look at some of them.
- Weight and adiposity reduction. Studies implementing the IF diet demonstrate a reduction in body mass index (BMI) of 4.3% and waist circumference by 3-8 cm12. Additionally, visceral fat is significantly reduced, while lean mass is maintained.
- It decreases total cholesterol, LDL, and increases HDL (good cholesterol).
- Clinical evidence has shown that it improves insulin resistance, reduces fasting glucose, and inflammatory markers. It is important to note that in diabetic patients, the use of this diet may cause hypoglycemia, so they must consult their physician.
- Circadian rhythm. Implementing intermittent fasting has shown positive effects on the circadian rhythm of eating. Limitations in the feeding windows allow for synchronization and have a positive effect on glucose levels, pancreatic function, body weight, metabolism, and oxidative stress.
- Cognition. The regulation of inflammatory markers has shown that intermittent fasting can have a neuroprotective effect. By influencing metabolic mechanisms, it optimizes neuronal bioenergetics, plasticity (capacity to learn), and stress resistance, thereby maintaining or improving cognitive performance. In fact, studies have shown that intermittent fasting improves memory, executive function, and working memory.
- Due to its action in improving cardiovascular health indicators, metabolism, adiposity, cellular repair, and cognition, intermittent fasting directly affects life expectancy. Furthermore, it has been found to stimulate the increase of growth hormone levels.
Intermittent fasting method for weight loss
It is advisable to transition to fasting at a rate that our body can handle. For this, it is suggested to start with the 16/8 protocol, which is easier to adapt to metabolically. It is important to note any symptoms of fatigue, tiredness, or headaches, as the absence of these symptoms is an indication that the same pace can be maintained or, conversely, that another diet modality should be considered.
As mentioned earlier, it is important to stay hydrated with calorie-free beverages during fasting. During meal times, the recommended intake should mainly consist of proteins, complex carbohydrates, fruits, and vegetables. The fats that are recommended to be consumed come from seeds or nuts, or from vegetable oils containing omegas, all in limited quantities. The attending physician may suggest the best suitable combination based on individual requirements.
What can you eat during intermittent fasting?
The proportion of foods follows the rule of which one provides the most calories... and fats are the most caloric. During fasting, you can drink non-energy drinks such as unsweetened coffee and tea, water, natural unsweetened lemonade or water with salt. During the eating period, it is suggested to mainly include proteins, complex carbohydrates, fruits and vegetables. The recommended fats are those that come from seeds or nuts, or from vegetable oils that contain omega, all in limited quantities.
How to control hunger?
The sensation of hunger follows a natural circadian rhythm. The hormone ghrelin is responsible for hunger, and its peak occurs around 8 p.m. When intermittent fasting begins, ghrelin levels increase during the first two days and then stabilize. This is because this type of diet synchronizes the circadian rhythm of hunger/satiety.
During those first two days, it is recommended to slowly consume abundant liquids in the form of sugar-free herbal infusions or "light" beverages (with sweeteners) to help alleviate hunger. Additionally, choose foods that provide greater satiety during meals by including more fiber, vitamins, and minerals. Engaging in physical activity such as yoga helps with relaxation and controlling the feeling of hunger.
Tips for Intermittent Fasting
- Drink water at regular intervals, as it helps with digestion and increases the feeling of fullness or satiety.
- Do not deprive yourself of water or calorie-free beverages (such as plain tea and coffee), which are allowed during fasting.
- The adaptation period lasts approximately one month, so be prepared and do not get discouraged.
- Maintain physical activity throughout the day to build muscle tone and "burn" fat. Exercise helps effectively digest and metabolize nutrients.
- After breaking a fast, focus on healthy and nutritious foods like vegetables, fruits, whole grains, and lean sources of protein.
- Try to eat earlier in the day, rather than at night before going to bed.
- Maintain a regular sleep schedule, as sleep helps your mind and body regain normal energy levels.
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- Canicoba, M. Aplicaciones clínicas del ayuno intermitente. Rev. Nutr. Clin. Metab. 2020; 3(2).
- Elortegui Pascual, P. et al. A meta-analysis comparing the effectiveness of alternate day fasting, the 5:2 diet, and time-restricted eating for weight loss. Obesity (Silver Spring). 2023 Feb; 31(Suppl 1): 9–21.
- Elsworth, R. L. et al. The Effect of Intermittent Fasting on Appetite: A Systematic Review and Meta-Analysis. Nutrients. 2023 Jun; 15(11): 2604.
- Fung, J. & J. Moore. The Complete Guide to Fasting. Victory Belt Publishing, 2016. ISBN 9781386313427.
- Liu, S. et al. The Health-Promoting Effects and the Mechanism of Intermittent Fasting. J Diabetes Res. 2023; 2023: 4038546.
