The intermittent fasting has been one of the most controversial issues of recent times, both in the sporting world, whether in health care. However, this popularity may not exactly match its true benefits and results, both physiologically and metabolically.
This practice corresponds to a dietary pattern in which food intake is limited to a short and defined period of time during the day . We can not talk about the term “diet,” since it tells us nothing about what foods should be included in a food plan, but about the time of eating. In fact, intermittent fasting takes place in any diet, being quite common in the low-carb and paleo models .
Before we go any further, it is important to make a note: whatever approach we take, we must realize what the impact on our health is,and whether it is sustainable as a healthy lifestyle.
The Different Ways of Intermittent Fasting
The popularization of this practice has led to the creation of several “methodologies” of how it should be done, existing of everything a little.
Time constrained feed (or 16: 8 method)
In this case, a period of time per day is defined in which the person can not eat, and the food is concentrated in the remaining moments of the day. The most common method is the 16-hour fasting, where meals should take place within 8 hours. For example, eat between 12:00 and 20:00.
Fasting on alternate days (or Eat-Stop-Eat )
Once or twice a week, fast between dinner one day and dinner the next day.
Full day fast
This case specifies dietary ratios, such as the 5: 2 diet, in which people eat about 25% of their usual calories (in two days) and have a normal diet on the remaining days.
After all, does fasting do good or bad for health?
There are those who argue that you can not eat for a while, but then we can eat whatever we want, no matter what. This situation can lead to behaviors with ” binge eating “, which is characterized by uncontrolled eating at open hours. On the other hand, there are more “sensible” methodologies that advocate a balanced diet most of the time and sporadically fast for a longer period, eating “blunders” very occasionally.
Intermittent fasting has been widely disseminated through social networks and other communication channels, and we now have access to a vast amount of information, not always from credible sources. The impacts and benefits of this practice on health are still little known.
One problem associated with this practice is the lack of scientific support in good methodological studies in humans on intermittent fasting . The results observed in animal studies can not in any way be used for us nor serve as a model for a new food style. They certainly realize that, as human beings, the scientific evidence that interests us is that obtained from studies done in humans, not in laboratory animals.
Studies with humans are very scarce and with several limitations, such as diet type, duration of fasting and study, or sample size. For these reasons, it is difficult to say whether the benefits of intermittent fasting are sustainable , especially in long-term health. In a very general way, the benefits of intermittent fasting would be:
- Losing weight and / or fat mass;
- Increased insulin sensitivity ;
- Reduction in inflammation;
- Lower oxidative stress.
Studies show different results among obese and with adequate weight
Overweight or obese people
It is noteworthy that intermittent fasting has been studied mainly as a strategy to lose weight for obese or overweight individuals. Under these conditions, studies have proven to be an effective method in reducing weight and visceral fat mass. However, similar results have also been observed by maintaining a hypocaloric diet. (1)
In addition to similar weight loss effects, intermittent fasting and caloric restriction showed reductions comparable to C-reactive protein (which is a marker of inflammation), total and LDL cholesterol, triglycerides, and blood pressure. (2,3)
A review of the study (4) reports that at the level of weight loss there are no differences between intermittent fasting and a restricted diet in energy . Therefore, we can not know if the benefits associated with intermittent fasting are due to this eating pattern or the fact of losing weight. In the above review, it is reported that little evidence exists supporting the idea that both daily calorie restriction and intermittent fasting lead to the same results in the control of type 2 diabetes mellitus, cardiovascular markers (cholesterol and triglycerides), and decreased inflammatory parameters. (4)
All this to say that at the metabolic level, the benefits of fasting depend entirely on the calorie restriction it induces. Since the available studies are short (1 day to 12 weeks), it is “stretching the rope” when it is said that intermittent fasting has a major impact on cardiovascular disease, cancer, diabetes and Alzheimer’s disease.
People who are lean or have adequate weight
In the case of studies in the sample, people who are lean or have adequate weight, intermittent fasting does not appear to have great benefits and, if used alone, does not counteract the negative effects of sedentary lifestyle (1, 6).
It is noteworthy that intermittent fasting was not tested in children, adolescents, the elderly or individuals who were in the process of hypertrophy, so it is not clear the effects to be observed in this group. From the psychological point of view, negative aspects were observed such as irritability, mood alteration, energy deficit and concentration (1). This may be due to decreased production of serotonin (also known as wellness hormone).
Conclusions on fasting: attention to eating disorders and your food goal
Although several studies reported the possibility of losing weight with intermittent fasting, some individuals showed weight gain due to the compensation they did on days when they were not fasting. This type of practice can result in eating disorder behaviors , and may create an unbalanced relationship with food in more susceptible individuals.
To finish, I highlight the main points to keep:
1) Scientific studies are lacking
Not necessarily against intermittent fasting, more studies are needed to assume a clear position as to its effects at the metabolic level.
2) It is not an exclusive practice to lose weight
There are no fixed rules regarding weight loss – intermittent fasting can be a strategy among the several that exist. It all depends on a personal choice!
3) Attention to calorie restriction
In weight loss, there must be caloric restriction, ie, ingest less than what is spent. However, not all strategies are “good” for maintaining muscle mass.
4) Consult a nutritionist before you start
If you opt for intermittent fasting, fine! Provided they do so sensibly and with nutritional monitoring.
5) It can be positive depending on how you handle the food
Intermittent fasting can be a viable option for staff who do not wake up hungry or have no organization or willingness to make the various snacks throughout the day. Intermittent fasting may be the best way to deal with food.
6) Prudence and wisdom above all else
This area still lacks scientific evidence so we must act with caution. If for you, it is the best way to achieve your goals, for other people it may not be. With regard to food, we must always pay attention to the individuality of each one.
Tips on Eating After a Fast
For those who intermittently fast (and for those who do not), you should always keep in mind the quality of the food. It is not because we fast that afterwards we can eat everything we feel like.
Attention to the first meal after a long period of fasting : this should be richer in protein and fat than in carbohydrates. If for yourself carbohydrates are “life”, opt for those with low glycemic index, such as fruits.