Pros and Cons of Intermittent Fasting 

Intermittent fasting (IF) describes the restricting or eliminating of one’s caloric intake for specified periods [1]. The two primary types of IF regimes are whole-day fasting, wherein one fasts for at least an entire day, and time-restricted feeding, in which caloric intake is limited to specific hourly windows during the day [2]. Since its surge in popularity, many alleged advantages and disadvantages of IF have come to light, but in some cases, the evidence backing them is tenuous [3]. This article will discuss the pros and cons of intermittent fasting, along with the evidence supporting these points, to assess the efficacy of this dieting strategy. 

The claimed benefits of intermittent fasting are numerous. They include short-term weight loss, increased brain-derived neurotrophic factor (BDNF), improved metabolic outcomes, reduced cancer risk, and slowed aging [1, 2, 4]. However, some of the claims of the pros of intermittent fasting are not well supported by existing research, and there are also the cons to consider. While various studies support the idea that, at least in some populations, IF can result in significant reductions in weight [5], some researchers have identified no difference in metabolic outcomes between IF and standard caloric restriction diets [1]. Additionally, the evidence supporting BDNF secretion is also unclear. Although IF increases BDNF levels and, thus, can produce mental health benefits in nonhuman animals, this result has not consistently carried over to human studies [1]. Similarly, it remains unclear whether IF causes slowed aging and decreased cancer risk in humans, suggesting that IF’s central benefit may be limited to weight loss [4].  

It is important to note that different forms of intermittent fasting produce different benefits. For instance, some researchers have identified an association between periodic fasting and weight loss, improved insulin sensitivity, decreased blood pressure, and lowered postprandial lipemia [6]. Meanwhile, time-restricted feeding seemingly led to sustained muscle mass and decreased fat mass in resistant-trained males according to one study; another, however, found no significant changes in weight among participants, while their oxidative stress decreased and their insulin sensitivity rose [6]. In view of this conflicting data, more research is necessary to confirm the benefits of these respective forms of IF. 

Having discussed the potential pros of intermittent fasting, we can now look at the cons. Fortunately, the most common risks associated with intermittent fasting tend to be moderate in nature [6]. They include fatigue, headaches, weakness, irritability, and halitosis [1, 6]. Nevertheless, more serious risks are possible: They can range from malnutrition, hypotension, insomnia, and anxiety [1]. Hypoglycemia may also occur in patients with Type 2 diabetes [5]. And women may be particularly vulnerable to risks because of the potential link between IF and adverse effects on reproductive and bone health [1]. 

Along with the possibility of adverse events, another disadvantage of IF is backsliding. As a reward for adhering to an IF regime, or perhaps as a result of fatigue or excessive hunger, people may engage in compensatory overeating [1]. Pre-existing emotional dysregulation or baseline disinhibition may be indicators of a person’s likelihood to engage in binge eating while on an intermittent fasting diet [1]. With adherence rates being reportedly low according to some studies [5], the risk of overeating is non-negligible and may jeopardize the overall success of the diet. 

Before deciding whether to direct a patient to adopt an IF regime, medical professionals should consider the pros and cons of the strategy in light of a patient’s individual circumstances. While intermittent fasting may not be appropriate for everyone, it may be an alternative to traditional weight loss methods. 


[1] S. Harding, “Intermittent Fasting: Clinical Considerations,” The Journal for Nurse Practitioners, vol. 17, no. 5, p. 545-548, May 2021. [Online]. Available:  

[2] R. L. Taft, “Intermittent Fasting for Weight Loss: Pros and Cons for People With Diabetes,” AADE in Practice, vol. 7, no. 4, p. 42-46, July 2019. [Online]. Available:

[3] G. M. Tinsley and B. D. Horne, “Intermittent fasting and cardiovascular disease: current evidence and unresolved questions,” Future Cardiology, vol. 14, no. 1, December 2017. [Online]. Available:  

[4] “Not so fast: Pros and cons of the newest diet trend,” Harvard Health Publishing, Updated July 31, 2019. [Online]. Available:  

[5] S. Anton et al., “The effects of intermittent fasting regimens in middle-age and older adults: Current state of evidence,” Experimental Gerontology, vol. 156, p. 1-8, December 2021. [Online]. Available:  

[6] R. Freire, “Scientific evidence of diets for weight loss: Different macronutrient composition, intermittent fasting, and popular diets,” Nutrition, vol. 69, p. 1-11, January 2020. [Online]. Available: