Written by: THE BALANCE
Medically reviewed by Dr. Sarah Boss, MD
Last updated: February 5, 2026
Fact checked
Quick Summary
  • Intermittent fasting, in particular time-restricted eating (TRE), has become the latest dietary trend and has been linked to some health benefits.
  • It includes restricting food intake within a certain time frame, which is usually less than eight hours.
  • Studies show that it may be beneficial for blood glucose control and cholesterol levels.
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Intermittent fasting, in particular time-restricted eating (TRE), has become the latest dietary trend and has been linked to some health benefits. It includes restricting food intake within a certain time frame, which is usually less than eight hours. Studies show that it may be beneficial for blood glucose control and cholesterol levels.

Although research suggests that it can lower cholesterol, others postulate an increased risk of cardiovascular death. One of the main shortcomings of the previous research is its dependence on observational studies. While these studies may indicate a probable positive effect, they do not necessarily prove causation. 

Randomized clinical trials, including time-restricted eating plans, need to be done to confirm these results. Besides, population-based health research with populations of different ethnicities can give a better understanding of its effects on different groups of people.

At Senses Wellness Clinic, our client-centered approach will enable you to take charge of intermittent fasting confidently and safely, which will not only improve your physical health but also your mental and emotional well-being. With customized strategies and active supervision, we help you begin the process of restoring good health and wellness. Let’s have a more in-depth look at the pros and cons.

Intermittent fasting (IF) is a schedule of eating and fasting that follows a cyclical pattern. (source: USPSTF, 2022)

IF is not a diet but a pattern of eating. It’s more about when you eat, not what you eat. This refers to the cycling between eating and fasting. It is like a food plan for your body.

How Does Intermittent Fasting Work

In the course of a fast, your body starts to utilize stored fats instead of sugar as an energy source. This metabolic shift may positively impact cardiometabolic health measures including several health markers [1]:

Blood Pressure: High blood pressure, or hypertension, for instance, is one of the major risk factors for heart disease and stroke. Some studies hint that intermittent fasting may be one of the ways of dealing with hypertension and thus, helping to keep the heart healthy.

Cholesterol Levels: When there is a high level of cholesterol in the body, particularly LDL cholesterol (often called the “bad” cholesterol), this is linked with a higher chance of cardiovascular disease. With intermittent fasting, LDL cholesterol levels are decreased and HDL cholesterol levels are increased (this is the type of cholesterol that is known as “good”).

Blood Sugar Control: Developing stable blood sugar levels is a key aspect of preventing type 2 diabetes and managing it. Intermittent fasting could help to improve insulin sensitivity, and thus, it can regulate the blood sugar level and minimize the chances of insulin resistance. [2]

Body Weight: Abdominal obesity is not only a major independent risk factor but is also closely associated with a variety of cardiometabolic disorders, such as cardiovascular disease and diabetes. Intermittent fasting has been proven to help with weight loss and reduce body fat percentage, which in turn may result in positive changes in risk factors for cardiovascular disease.

Inflammation: Inflammation for a long time is thought to be the reason for the emergence of cardiovascular disease and metabolic disorders. Evidence indicates that intermittent fasting can decrease inflammatory markers in the body, and therefore it contributes to the overall cardiometabolic health.

Insulin Resistance: When the cells in the body become less sensitive to the effects of insulin, they are not able to lower the blood sugar levels effectively, which results in high blood sugar levels. Intermittent fasting can improve insulin sensitivity and lowers the risk of insulin resistance and diabetes which may lead to cardiometabolic problems.

Types of Intermittent Fasting

There are several ways to practice IF, each with varying levels of restriction [1]:

Time-restricted eating (TRE): This is the most frequently used type of intermittent fasting, which is limiting your eating time to a shorter eating duration, usually within an eight-hour window. (source: NIH NLM, 2020)

Alternate-day fasting (ADF): You take turns doing normal eating days and restricted calorie days (around 500 calories).

5:2 diet: This type of diet involves eating normally for 5 days and then having a calorie-restricted diet on 2 non-consecutive days.

Eat-Stop-Eat: The method is based on the complete fasting for 24 hours which is done once or twice a week.

Who Should Avoid Intermittent Fasting

Although intermittent fasting can work well for some people, it is not suitable for everyone and therefore should be used with caution. Intermittent fasting cardiovascular risk increases in vulnerable individuals, so it is not recommended for them.

Healthcare experts typically advise the following groups to steer clear of intermittent fasting [2]: (source: ClinicalTrials.gov, 2025)

  • Have diabetes
  • Have heart, kidney, or liver disease
  • Have a history of an eating disorder or disordered eating
  • Expectant mothers and breastfeeding moms
  • Children and teenagers
  • Frail older adults
  • People with weakened immune systems
  • Individuals in eating disorder recovery or with current eating disorders
  • People with dementia

It is also important to mention that anyone with a history of traumatic brain injury or post-concussive syndrome is highly susceptible to the adverse effects of intermittent fasting.

If you have a medical condition or are under medication, it is imperative to talk with a trusted healthcare provider who can explain the possible benefits and risks of intermittent fasting.

So despite the many reported benefits, why is intermittent fasting bad?

IF has been advocated for several traditional cardiometabolic risk factors, yet it has its hidden downside. While it might not be directly associated with adverse effects on the heart, it can indirectly affect the health of your health by the following side effects [2]:

Hunger and Cravings

It is easy to see that hunger is numbered of the most common effects of intermittent fasting. (source: World Health Organization)

When you are on a low-calorie diet or you eat less food for a long period, you are likely to have strong urges for food.

A study in the year 2018 that involved 112 persons was done with some study participants assigned to the intermittent energy restriction group. Each individual will have to follow the diet regimen of either 400 or 600 calories on two nonconsecutive days per week for a year.

The groups fasting on low-calorie intake with continuous calorie restriction reported higher hunger levels than the groups following a low-calorie diet.

Likewise, in 2020 another study of 1422 people who had been fasting 4-21 days was conducted. The vast majority of individuals who took part in the diets did not report hunger symptoms until the first few days of the routines.

Consequently, side effects like hunger may be reduced with time once your body is accustomed to fasting on regular occasions. (source: AHA, 2024)

Headaches and Lightheadedness

In a fasting method, headaches may be encountered as a consequence, usually in the first few days of fasting when your body is still adjusting to the new eating pattern.

An investigation of the studies of 2021 that were reviewed, from a set of 18, which included people who were undergoing intermittent fasting regimens. In a study that examined the side effects of the drug, some of the participants reported experiencing mild headaches.

Among other findings, a study from 2010 determined that “fasting headaches” are usually localized in the frontal brain section and tend to be of mild to moderate intensity. People with a history of headaches tend to experience them more often during fasting than those without headaches.

These studies point out that the causes of headaches during intermittent fasting might be low blood sugar levels and caffeine withdrawal.

Digestive Issues

These symptoms including indigestion, diarrhea, nausea, and bloating may occur as side effects of intermittent fasting. [7]

Intermittent fasting might be the cause of these symptoms as it reduces food intake, which in turn, can disrupt the digestion process. Besides, intestinal gas and diarrhea could also be experienced by some people due to dietary modifications associated with intermittent fasting.

Consuming foods that are high in nutrients, especially fiber, could be a relief since these digestive problems are one of the reasons why they are felt.

Irritability and Mood Changes

People may be grumpy and have ups and downs in their moods when intermittent fasting is practiced as a result of low sugar levels in the blood.

Sometimes low blood sugar, called hypoglycemia, may happen with a low-calorie diet or during fasting hours. This may result in:

·         Irritability [8]

·         Anxiety

·         Impaired concentration

A 2016 study that involved 52 women showed that the participants experienced significantly higher levels of irritability during an 18-hour fasting period compared to non-fasting periods.

However, the participants found themselves more irritable throughout the fasting period compared to the beginning.  On the other hand, at the end of the fasting period, they also had a feeling of accomplishment, pride, and self-control compared to the beginning.

Sleep Disturbances

This is true for some people who complain about sleep issues, such as the inability to fall asleep or stay asleep, as a result of intermittent fasting. (source: NIH (NHLBI), n.d.)

An analysis carried out in 2019 on 1,422 people who engaged in fasting practices for 4-21 days was the subject of the study. Preliminary research showed that 15% of participants who were fasting told that they had sleep disturbances. This was the most common complaint out of all other reported side effects.

In the beginning of intermittent fasting, fatigue can be a common symptom, since our bodies lose large amounts of salt and water through urine. As a result, the process may cause dehydration and lower salt levels. Nevertheless, the literature brings contradictory results and intermittent fasting is not shown to influence sleep patterns.

A study in 2021 conducted on 31 people with obesity showed comparable results to a group of people who followed an alternate-day fasting regimen. Also, in this study, the participants had a low-carb diet for six months. The findings showed that implementing this approach did not lead to changes in sleep quality, duration, and the severity of insomnia.

The latest research by Shanghai Jiao Tong University School of Medicine has led to some worries about the possible side effects of intermittent fasting. The findings of the study suggest that intermittent fasting is associated with a 91% chance of death from heart disease [3]. This extremely high risk of cardiovascular death is a shocking figure. This finding calls into question the idea that intermittent fasting might be a panacea for health and may serve as an incentive for further examination of its possible downsides.

The research, which was conducted on a large sample of people, found an alarming link between intermittent fasting and cardiovascular death. The fact that it is popular as a weight loss method and has purported health benefits does not mean that it is not a very serious risk factor for heart health. (source: NICE, 2023)

While intermittent fasting is popular for being able to lose weight, improve metabolism, and reduce the risk of chronic diseases, including cardiovascular disease, the dark side of this study should not be underestimated. The main concern, however, lies with the increased risk of cardiovascular mortality, which in turn questions the safety and long-term effects of intermittent fasting as a dietary strategy.

Nevertheless, it should be remembered that this study is one component of the whole picture and more research is required to verify and expand on these findings. It’s important to consider some limitations. The study relied on self-reported dietary information, which can be inaccurate. The American Heart Association emphasizes the importance of population-based health research. Future studies with more objective food intake data could provide a clearer picture of the potential benefits and risks of time-restricted eating (TRE).

Along with that, individual variables like age, gender, and underlying health conditions are other factors that can determine the link between intermittent fasting and the risk of heart disease.

The future of IF needs to take into account the pluses and minuses of the practice, to come up with a balanced approach. IF has been widely accepted because of its supposed health benefits, recent studies with cautionary findings such as a significantly higher risk of death from cardiovascular diseases, should be approached with much apprehension.

The promotion of intermittent fasting should go hand-in-hand with an in-depth analysis of its impact on various aspects of health, such as cardiovascular health, metabolic function, and general health. This assessment should be done considering individual variation, the health condition of the person, and compliance with fasting protocols. (source: BMJ, 2021)

In addition to this, it is necessary to elaborate on the mechanisms that are responsible for the possible effects of intermittent fasting and also to identify those groups of people who may be at a higher risk of adverse cardiovascular outcomes. Long-term studies with bigger population samples are required to give more accurate and reliable proof of the safety and effectiveness of intermittent fasting in various groups of people.

Personalized healthcare professionals are the key to guiding those individuals who are considering fasting intermittently, and they give recommendations based on a person’s medical history, lifestyle, and targets. The truth is that it is crucial that one has to consider the benefits and the risks and then decide whether intermittent fasting is suitable for him/her or not.

Ultimately, the promotion of intermittent fasting needs to be done with caution, highlighting the fact that such an approach should be individualized, the patients should be closely monitored, and ongoing research is mandatory to ensure the safety and efficacy of this dietary intake strategy. If intermittent fasting fits the profile of some individuals, it is not a panacea, and its adoption should be combined with a cautionary attitude and professional advice.

At Senses Wellness Clinic, we offer professional support with a holistic approach for effective intermittent fasting. By employing individual counseling, our clients are taught to observe fasting regimens with accuracy. We perform comprehensive evaluations to make sure that intermittent fasting is appropriate for each individual, taking into account medical history and lifestyle. Through monitoring cardiovascular health indicators such as blood pressure and cholesterol levels, we make sure fasting is carried out safely. 

FAQs

Is Fasting Safe For Heart Patients
The safety of intermittent fasting for heart patients is subject to several aspects including the person’s general health, medical history, and current plan of treatment. Some researchers have shown a positive effect on heart health, for example, lower blood pressure and cholesterol, but fasting may not be right for every heart disease patient. Patients with heart conditions need to consult with their healthcare provider before starting any fasting program.
Does Intermittent Fasting Influence Hormone Levels?
Indeed, intermittent fasting can lead to alterations in the levels of hormones in the body like insulin, cortisol, and growth hormone. An instance of this is that fasting intervals result in increased insulin sensitivity and cortisol secretion alterations.  These may have metabolic and energy regulation implications.
Is Intermittent Fasting Appropriate For Athletes Or Active People?
Intermittent fasting may have different results among people with different levels of physical activity. Even though some athletes and active people could be able to adhere to intermittent fasting and achieve their performance goals, others could experience energy level, recovery, and muscle mass loss issues. It is highly necessary to take into account individual needs and seek advice from a sports nutritionist or healthcare provider.
Can Intermittent Fasting Be Combined With Ketogenic Dieting?
Of course, these two methods can be used together, including the ketogenic diet. This combination, which is commonly called “keto fasting”, is simply the alternation of fasting with the consumption of a so-called “keto diet” that is rich in fats and low in carbohydrates. Some people may want to try this method as a tool for weight management, metabolic health, and cognitive performance.
Are There Any Potential Psychological Effects Of Intermittent Fasting?
The psychological effects of intermittent fasting on those individuals may include mood, cognition, and eating behavior changes. Those people may have improved mental clarity and focus during fasting, on the other hand, others may show mood swings, irritability, and feelings of deprivation. It’s indispensable to keep an eye on one’s mental health and get help if needed, especially when one practices fasting.
Is Intermittent Fasting Adaptable To People With Individual Dietary Choices Or Limitations?
Certainly, intermittent fasting can be tailored to accommodate diverse food choices and limitations like vegetarianism, veganism, or religious dietary practices. For instance, people adopting a plant-based diet can organize their fasting and eating windows accordingly, so that nutrient intake is ensured while the potential benefits of intermittent fasting are achieved. A registered dietitian or nutritionist can be consulted to adjust the fasting protocols to every individual’s needs and preferences.

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