The Science Behind Intermittent Fasting
Intermittent fasting and calorie restriction continue to gain popularity as effective methods for losing weight and adopting a healthier lifestyle. However, does the science support these benefits?
Intermittent fasting involves alternating periods of fasting and non-fasting. These methods include alternate-day fasting (one day non-fasting, next day fasting), the 5:2 method (regular eating for five days and fasting for two), and others.
Calorie restriction is a continuous regime of limiting daily calorie intake.
The research paper “Health effects of intermittent fasting: hormesis or harm? A systematic review.” [1] Conducted a comprehensive and methodological review of evidence through various criteria [1]. This paper aims to identify research up to January 2015 that provides strong evidence that these fasting methods benefit people [1]. In doing so, the findings from this review came from five reports [1].
What Does the Science Show?
One of these studies spread over 12 weeks with 32 non-obese subjects who conducted alternate-day fasting and lost 6.5% of their body weight [1]. There were also indicators of improvements in cardiovascular and metabolic health [1]; however, the design of the experiment may have weakened the reliability of these results [1]. The study also did not evaluate the safety of fasting [1], thus raising questions about its appropriateness for medical applications.
Another study with 32 subjects over 12 weeks found that the subjects were in angry, tense, and confused moods [1]. In addition, there were changes in blood pressure, total cholesterol, LDL cholesterol, weight, and fat mass [1]. However, this review fails to mention whether these changes are positive or the extent of these changes. Therefore, these particular results cannot be analysed. Again, no data on the safety of fasting was gathered [1].
In addition, the paper also mentions a separate study that initially investigated how smoking rates in certain states affected cardiovascular disease risk [1]; however, when they wanted greater insight into the low risk of cardiovascular disease in these states, they investigated the fasting histories of the subjects [1]. They found that those who conducted routine fasting had a lower risk of cardiovascular disease compared to those who did not fast [1]. They also found that fasting in this group results in lower chances of diabetes [1].
An additional study investigated similar variables with a different cohort and had the same results as the previous study [1], thus seeming to display the accuracy and validity of the health benefits of fasting. It also found that fasting led to lower glucose concentrations and BMI (body mass index) [1], thus strengthening evidence that fasting could decrease the chances of diabetes. However, this article does not mention what specific method of intermittent fasting these studies conducted.
Can We Trust These Results?
What limits previous studies is the lack of dietary history recorded [1]; thus, perhaps other factors may have caused these results. Furthermore, different intermittent fasting methods may have different effects on health, such as having better effects on diabetes and cardiovascular disease [1].
Potential Safety Concerns.
In addition, there is a significant lack of safety data on intermittent fasting [1], with suggestions that it could cause harm if conducted too frequently or for too many consecutive days [1]. Thus, having timelines for the best and most considerable fasting period could significantly increase the safety of fasting.
Moreover, fasting can result in headaches, light-headedness, dehydration, weakness, eating disorders, malnutrition, a greater risk of disease, and damage to organs [1].
A study in rats displayed that alternate-day fasting caused left atrial diameter damage, mycofridabl fibrosis, and reduced cardiac reserves [1], thus indicating that perhaps intense intention fasting may be damaging to humans [1]. Therefore, there needs to be significant research to ensure that this method is safe and appropriate for people [1].
How Can We Start Taking Intermittent Fasting Seriously?
It is essential that for intermittent fasting to move on from just a popular weight loss method to clinical advice, there need to be significant advancements in research on humans for health benefits and the safety of people in the short and long-term as well as in different circumstances (such as diets, diseases, heights, weights, health histories, etc.) [1].
In conclusion, the paper reports that there is significant evidence for benefits when it comes to decreasing cardiovascular disease risk and metabolic risks [1] and that various animal studies that show significant health benefits and improvements in longevity [1] should highly encourage further human trials into the effectiveness and safety of fasting, especially in those that are healthy, have improved health, suffer from diseases, and are high-risk individuals [1].
A reminder that this is not medical advice and that people must consult with their doctor before making any drastic changes to their diet. These methods do not affect or suit everyone the same; thus, it is always important to consider your case.
References
Reference paper “Health effects of intermittent fasting: hormesis or harm? A systematic review.”