Is Intermittent Fasting Bad for Your Heart Health?

With many people looking at weight-loss options for either appearance or health reasons, one approach that has gained popularity in recent years is intermittent fasting (IF). However, a recent study suggests that intermittent fasting could negatively affect cardiovascular risks. What are the facts?
What is Intermittent Fasting?
Intermittent fasting alternates cycles of eating and going without food. Studies have suggested that IF may have cardioprotective functions and may reduce the incidence of diabetes, among other benefits. Some studies say that intermittent fasting may lower levels of low-density lipoprotein (LDL) cholesterol, often known as the “bad” cholesterol.
Intermittent fasting also may improve the body’s response to a hormone called insulin. Insulin helps control blood sugar levels. Higher LDL cholesterol and higher blood sugar levels in diabetes are risk factors for heart disease.
Some studies demonstrate greater weight loss and fat loss with intermittent fasting than with regular calorie cutting, while another review of studies found that weight and blood sugar improvements were small. Research results on intermittent fasting are mixed, and longer studies have not confirmed the benefits.

Types of Intermittent Fasting
Time-Restricted Eating
For this type of fasting, calories are consumed within a specific time period that usually matches our circadian rhythms. Examples could be eating between the hours of 7 a.m. and 7 p.m. (a 12-hour window) or between 8 a.m. and 4 p.m (an 8-hour window). “After-hours” consumption is typically limited to liquids like water, black coffee, or unsweetened tea.
Alternate Day Fasting
The most common type of alternate day fasting includes days of eating normally alternating with days of only consuming about 500 calories or so.
5:2 Fasting
A variation of alternate day fasting is 5:2 fasting. With this approach, you eat normally five days a week. Calories are restricted to 500-600 per day the other two days of the week. The two days should have at least one non-fasting day between them.
What are the Benefits?

According to the National Library of Medicine, intermittent fasting has demonstrated the potential for weight loss, improved sleep and energy, and decreased appetite. Another report relates improvements in asthma, seasonal allergies, heart arrhythmias, menopausal hot flashes and more. The 5:2 fasting approach in particular seemed effective at reducing insulin levels and improving insulin sensitivity.
Obesity is a major medical problem around the world. IF may reduce body fat and inflammation and improve glucose metabolism. For non-obese people, it may also lower C-reactive protein (a marker for inflammation) and help the hormone leptin control hunger and appetite.
“Our culture has a very high burden of cardiometabolic disease, including type 2 diabetes, hyperlipidemia, obesity, and insulin resistance,” says Briana Costello, MD, FSCAI, an interventional cardiologist with Covenant Health’s Knoxville Heart Group.
“If done correctly, intermittent fasting can provide people with structure so that there are fewer ‘excess’ calories consumed. People who struggle with overconsumption of calories or portions may benefit from intermittent fasting for this reason. A recent article in Nature Medicine illustrates these effects on our metabolism.”
What are the Drawbacks?
Sources suggest that IF can have negative side effects. These may include:
- Dehydration, bad breath
- Dizziness/light-headedness or weakness
- Digestive issues or nausea
- Headache
- Insomnia and fatigue
- Irritability/mood changes
- Low blood sugar (hypoglycemia)
- Malnutrition, if fasting is done improperly with note enough emphasis on nutrition
Another drawback of intermittent fasting is that “when people hit the ‘time to eat’ they find themselves overeating or choosing unhealthy foods that are quick fixes for their hunger,” Dr. Costello notes.
Is Intermittent Fasting Really Bad for Heart Health?
A preliminary study released by the American Heart Association in 2024 suggested that time-restricted eating actually may be linked to a higher risk of death from heart disease. The AHA report looked at 20,000 adult participants in a multi-year study. Results showed a 91% higher risk of death from cardiovascular disease among those who restricted eating to a window of 8 or fewer hours compared to those who ate within a 12-to-16-hour window. The increased risk of death was also seen in persons living with heart disease or cancer.
It’s important to note, however, that although the study indicated an association, it does not mean that time-restricted eating caused cardiovascular death. More long-term research and peer-reviewed studies are needed to see how intermittent fasting affects heart health.
Is Intermittent Fasting Right for You?
Intermittent fasting is not recommended for everyone. You should check with your medical provider before beginning IF. Persons who generally should not use intermittent fasting include:
- Children/adolescents
- Individuals taking certain medications (consult your medical provider)
- Individuals with diabetes, kidney disease or heart-related issues (consult your medical provider)
- Individuals with a history of eating disorders
- Those with low blood pressure
- Women who are pregnant or breastfeeding
“Patients on insulin therapy should certainly consult with their endocrinologist when considering intermittent fasting and should be sure to check blood sugar more frequently. Insulin therapy may need adjustment when fasting, especially with significant weight loss,” Dr. Costello says. “Pregnant women should exercise caution with fasting, especially if they are starting pregnancy underweight.”
Short-term studies suggest there is greater weight loss with intermittent fasting than with regular calorie cutting. Some people do find intermittent fasting to be easier than continuous calorie restriction. However, IF has about the same adherence rate as traditional dieting.
Finding Your Best Strategy for Heart Health
Regardless of the method you choose for losing weight or improving your heart health, Dr. Costello encourages working with your medical provider and using approaches to healthy eating and exercise that have proven to be effective.

“The first thing I try to do with patients who need to make dietary changes is to figure out what the real problem is,” Dr. Costello says. “Is it snacking after dinner? Food choices while at work? Is the diet too high in carbohydrates? Once we identify the issues, then I try to work with patients on how to fix the problems.” She adds that she is “a huge proponent of the diet that has proven time and time again to decrease cardiovascular events: the Mediterranean diet.”
“Beyond that, I emphasize avoiding drinking empty calories – such a waste! – and trying to avoid processed or packaged food as much as possible. I do not believe in ‘cutting out’ anything a patient loves, because then they want it more. Life is a balance – if you love cookies, that’s fine. But limit it to one cookie every other day to keep you satisfied.
“I am also a big fan of doing 30 minutes of any exercise you want every day. Exercise not only helps prevent heart attacks and strokes, but dementia as well.”
Covenant Health has additional information about improving heart health, along with information about risk factors, types of heart disease, and when to see a doctor. To find a Covenant Health physician for your needs, visit CovenantHealth.com/find-a-doctor/. Learn more about Covenant Health’s cardiology services at Heart Care – Covenant Health.

Covenant Health
Headquartered in Knoxville, Tennessee, Covenant Health is a not-for-profit, community-owned, healthcare enterprise committed to providing the right care at the right time and place. Covenant Health is the area’s largest employer and has more than 11,000 compassionate caregivers, expert clinicians, and dedicated employees and volunteers.