In recent years, intermittent fasting has gained popularity due to its potential health benefits and weight management advantages. The concept suggests that it’s simpler to drastically reduce calorie intake a few days per week or restrict eating to a shorter “eating window” each day than to moderately decrease calories during every meal, every day.
Advocates assert that prolonged fasting periods (beyond the typical time between meals) can enhance cellular repair, improve insulin sensitivity, raise levels of human growth hormone, and modify gene expression to promote longevity and protection against diseases. However, are there any associated risks?
To evaluate its side effects, it’s essential to understand that there are different types of intermittent fasting, and the evidence regarding its long-term safety and effectiveness remains unclear. The most common types are:
- Alternate day fasting (ADF), where fasting is required every other day.
- Modified alternate-day fasting, which entails consuming only 25 percent of your usual intake every other day.
- Periodic fasting, which involves limiting food to about 500 to 600 calories per day for only two days each week.
- Time-restricted eating, which restricts your daily “eating window.”
While some plans may result in more side effects than others, it’s crucial to discuss the potential intermittent fasting side effects with a medical professional before selecting a plan that suits your lifestyle.
Overeating
Overeating may be a potential risk of intermittent fasting. When food is restricted, the appetite hormones and hunger center in the brain become hyperactive, leading to a strong biological urge to overeat.
According to Dr. Frank Hu, Chair of the Department of Nutrition at the Harvard T.H. Chan School of Public Health, people tend to reward themselves after prolonged fasting or challenging exercise, leading to the risk of indulging in unhealthy eating habits on non-fasting days.
Research indicates that intermittent fasting can cause similar effects as calorie-restricted diets, such as a slowed metabolism and increased appetite. A 2018 study found that these effects are just as likely with intermittent fasting as they are with daily calorie-cutting. Studies on time-restricted eating have also suggested that eating during periods that conflict with the body’s natural circadian rhythm could lead to metabolic issues.
Dehydration
Dehydration is a potential side effect of intermittent fasting, as the body loses both salt and water through urination, particularly during the initial 2-4 days of fasting. Excessive salt and water loss can lead to dehydration.
Early signs of dehydration include dizziness, fatigue, and headaches. If you experience any of these symptoms during fasting, it’s recommended to increase your water intake. Severe dehydration can also impact cognitive functions such as attention, memory, and mood.
To prevent dehydration during fasting, it’s essential to drink enough water. Checking the color of urine can be helpful; if it’s dark, it could indicate dehydration.
Fatigue and brain fog
Feeling excessively tired or experiencing brain fog can be a sign that your intermittent fasting plan may not be suitable for your body or lifestyle. Skipping breakfast during intermittent fasting can lead to fatigue or difficulty concentrating, especially if you’re not consuming enough nutrient-dense foods during non-fasting hours.
It’s crucial to pay attention to what you eat during non-fasting hours to ensure that your body is getting the necessary nutrients to function properly. If you feel much better when eating breakfast, then intermittent fasting may not be the best approach for you, and it’s essential to listen to your body’s needs.
Sleep problems
Intermittent fasting may initially cause sleep disruptions due to changes in meal times that affect the body’s natural sleep-wake cycle or circadian rhythm. However, research suggests that overall, it may actually improve sleep quality.
A review of studies examining the impact of intermittent fasting on sleep found no significant negative effects. In fact, some studies even suggested that intermittent fasting could lead to better sleep quality.
If you experience sleep problems when starting this type of fasting, it’s likely due to your body adjusting to the new schedule. These problems should improve over time.
Summary
Even though intermittent fasting has been linked to several health benefits, it may not be suitable for everyone. If you decide to try intermittent fasting, be aware of these mild side effects.
Although most of them tend to go away on their own with time, you can alleviate them by drinking more water and making other small adjustments. But if the side effects are uncontrollable and won’t go away, you might have to change your fasting schedule, and necessarily consult with a healthcare professional.
Certain individuals, such as pregnant women, older adults, people with type 1 and type 2 diabetes on certain medications, and individuals with a history of disordered eating, should avoid intermittent fasting.
