Three cons of intermittent fasting (IF) include short-term side effects like headaches, fatigue, and irritability; the difficulty in meeting nutritional needs and potential for nutrient gaps; and social/lifestyle challenges, making adherence hard and potentially creating an unhealthy relationship with food, especially for vulnerable individuals.
It can be a lifestyle change ― and one with benefits. Keep in mind that intermittent fasting may have different effects on different people. Talk to your doctor if you start experiencing unusual anxiety, headaches, nausea or other symptoms after you start intermittent fasting.
A study of over 20,000 adults found that those who followed an 8-hour time-restricted eating schedule, a type of intermittent fasting, had a 91% higher risk of death from cardiovascular disease. People with heart disease or cancer also had an increased risk of cardiovascular death.
For example, a news release published last year after an American Heart Association meeting reported some potentially concerning findings — namely, that people who followed an 8-hour, time-restricted eating schedule, a type of intermittent fasting, had a 91% higher risk of dying from heart disease.
Anyone under 18, those who are pregnant or breastfeeding, and individuals who have had disordered eating should avoid intermittent fasting. If you have certain medical conditions or take certain medications, intermittent fasting may impact them, so it's important to discuss it with your doctor.
Don't Break Your Fast
The golden rule in fasting is that it is a fast, this means no calories, no nutrients, no food. Even breaking the fast slightly with some food can throw severely limit the benefits you'd otherwise experience.
As blood glucose levels fall during fasting, the pancreas secretes increased amounts of glucagon. This action also reduces insulin secretion, which in turn decreases glucose storage in the form of glycogen.
Regardless of the intermittent fasting form people choose, they tend to make the same five common mistakes:
Ideally, the association of fasting and lower blood pressure levels means a possible decrease in hypertension-related complications due to the reduction of the workload on the heart. However, the evidence supporting the direct impact of fasting on cleaner arteries is not conclusive.
Understanding the 3-3-3 Rule
Specifically, the rule suggests: Three balanced meals per day. Three hours between each meal. Three hours of movement per week.
Following an intermittent fasting skip dinner approach might be better aligned with your circadian rhythm. This way, you can improve digestion and sleep by preventing late-night overeating. Beginning your intermittent fasting with breakfast early in the morning can also help reduce your overall calorie intake.
Intermittent fasting and energy-restricted diets are effective in improving circulating total cholesterol, low-density lipoprotein cholesterol, and triacylglycerol levels. However, intermittent fasting and energy-restricted diets have no meaningful effects on high-density lipoprotein cholesterol levels.
While intermittent fasting may offer benefits, it also carries risks for older adults—especially those with existing health conditions.
Eat a higher-protein, low-carb breakfast instead, like meat and nuts, an omelet, or a low-carb protein shake. Just don't knock the intermittent fasting unless you've really tried it.
While it has been shown to help people lose excess pounds, intermittent fasting is often labeled as a fad diet. In addition, a retrospective study presented at an American Heart Association conference in March 2024 claimed intermittent fasting was linked to a higher risk of death from heart disease.
Pregnant or breastfeeding people have increased energy needs and shouldn't engage in calorie restriction. 5 Intermittent fasting may also reduce your chances of becoming pregnant and should be avoided if you're trying to conceive. 6. You have diabetes or blood sugar issues.
Early research presented at a recent scientific meeting suggested that intermittent fasting might be harmful or risky in general. It showed that people practicing intermittent fasting are twice as likely to die from heart disease or die in general than those who don't practice.
The absolute most important rule is “don't break your fast." It's more important than how many calories you eat each day, or how you structure your meal timing. The core principle needed to take advantage of intermittent fasting is consecutive non-eating hours.
When learning how to intermittent fast for weight loss, it helps to keep in mind that intermittent fasting is not a quick weight loss method; it might take a while for you to lose your first kilogram. Some people lose about one kilogram per week, while others can drop up to 5 kilograms in one month.
Stool production is significantly reduced during long-term fasting.
Signs You're Benefiting From Intermittent Fasting
For some, fasting may cause problems. For example, studies have found that people who regularly fast more than 16 or 18 hours a day have a higher risk of gallstones. They're also more likely to need surgery to remove the gallbladder.