Intermittent fasting (IF) is a diet pattern that has received a lot of attention due to its potential health benefits. Some IF users report more energy, weight loss, and improved metabolic health. (1) But intermittent fasting isn’t right for everyone. Here are some health considerations to think about before you begin.
Some research suggests that people with certain health conditions, such as health conditions that affect digestion or blood sugar, or those in certain life stages, should use caution before starting intermittent fasting. (4) Let’s break down the research-based considerations to help you decide if intermittent fasting is right for you and your lifestyle.
Medical Conditions and Medications: Who should avoid intermittent fasting?
Before jumping on the intermittent fasting bandwagon, you should consider your personal medical history, any medications you are currently taking, and, as always, consult your doctor. In particular, people with diabetes, kidney stones or gastroesophageal reflux disease should approach fasting cautiously and receive individualized advice before starting a fast. (4)(5)
Additionally, if you are taking medications for heart disease, blood sugar, high blood pressure, or medications that require food for proper absorption, intermittent fasting may affect the functioning of those medications or cause negative side effects. (6) and people with a history of eating disorders should avoid intermittent fasting. That’s because any type of diet plan can lead to unhealthy patterns associated with food restriction and binge eating. (7)
Health conditions that may make intermittent fasting a bad idea
If you are taking medication for a medical condition, including heart disease, diabetes, high blood pressure, or medications such as insulin and blood thinners, you may need regular intake of food for proper absorption and intermittent fasting may not be right for you . (6)
Other health conditions that may make intermittent fasting the wrong approach include:
- diabetes: Fasting can affect your blood sugar levels, causing them to drop to dangerous levels or cause unpredictable spikes. (4)
- kidney stones: Fasting may increase the risk of stone formation by affecting hydration status and meal intake.(5)
- underweight individuals: Fasting can lead to additional weight loss, so it should be done under the supervision of a doctor and through regular health checkups. (8)
- History of Eating Disorders: Fasting can lead to unhealthy eating habits and may not be safe for people with past or current eating disorders. (7)
How Intermittent Fasting Affects Metabolism
One of the most widely discussed benefits of intermittent fasting is its effect on metabolism. Studies have shown that fasting initiates fat burning through a process called ketosis. This is when your body burns fat for energy in the absence of carbohydrates. (1)
Intermittent fasting can also improve insulin sensitivity, which can lower blood sugar levels and improve blood sugar control, potentially reducing the risk of developing type 2 diabetes. (9)
However, some notable studies indicate that when put head-to-head with other types of calorie-restricted diets, fasting is not associated with greater weight loss than other types of calorie-restricted diet plans. (10)
This means that any type of diet that’s right for you can help you achieve your weight loss goals, even if you’re not suited to fasting.
Another metabolic benefit is autophagy, a cellular repair and regeneration process that occurs with any type of calorie restriction. (11) This process is associated with longevity and can help prevent age-related diseases by eliminating damaged cells. (11)
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Hormonal Effects: Why Fasting Is Different for Women
Because women’s bodies are very sensitive to changes in calorie intake, intermittent fasting may affect female hormones such as estrogen and progesterone. (12)
Studies have shown that prolonged fasting can disrupt a woman’s reproductive hormone balance, potentially leading to irregular menstrual cycles and unpleasant symptoms. (12) Importantly, it is recommended that women trying to become pregnant avoid long fasting periods, as calorie restriction can negatively impact fertility. (12)
For women who are pregnant or breastfeeding, fasting can lead to nutritional deficiencies and insufficient calorie intake, which can affect the health of both mother and baby. (13) If you are a woman at this stage, talk to your health care team before trying intermittent fasting.
Even when not pregnant, women with hormonal imbalances such as polycystic ovarian syndrome (PCOS) should be careful about fasting. It may worsen your symptoms. (13)
Ultimately, some research suggests that women may benefit from shorter fasting periods, such as 12 to 14 hours, instead of a more restrictive 16-hour schedule. (14)
About our experts:
Caroline Thomason A nutritionist and diabetes educator who combines a love of nutrition and the power of making better health easy to understand. During her 12 years in the industry, she has published in more than 40 publications and served as a CPG consultant and advisor, speaker, on-air spokesperson, and recipe developer.
Joanna Gregg, RD a is the food data curator at MyFitnessPal. She earned her bachelor’s degree in nutrition from Georgia State University and her master’s degree from the University of Nebraska.
Cortisol and Stress: The Science of Fasting and the Stress Response
Intermittent fasting may also affect levels of cortisol, a hormone that manages the body’s stress response. (15)
Long periods of fasting can increase cortisol production, especially if you are already stressed or sleep-deprived. (15) Elevated cortisol levels appear to be associated with weight gain, especially in the abdominal area, which may offset the weight loss benefits associated with fasting. (16)
Moreover, high cortisol levels can make eating stressful at the end of a fasting period, creating a vicious cycle of overeating followed by limited fasting. (17) This is a form of irregular eating, and if you find yourself falling into this pattern, fasting may not be for you. (17)
Overall, if you’re prone to stress or have trouble managing stress-related cravings, intermittent fasting may not be the best option for you.
Blood Sugar Sensitivity: Who Should Watch Out?
If you have concerns about blood sugar levels, such as diabetes or hypoglycemia, you should be especially careful about intermittent fasting. (4) Fasting can improve insulin sensitivity, but long-term fasting can be dangerous for people with diabetes because it can cause blood sugar levels to drop dangerously low. (9)
Fasting, especially if you take insulin or other medications that affect blood sugar, may increase your risk of hypoglycemia, which can cause serious symptoms such as dizziness, brain fog, confusion, or fainting. (18)
Even in people without diabetes, prolonged fasting can cause a drop in blood sugar, which can lead to irritability or general fatigue. (19) If you have a blood sugar-related condition, consider a shorter fasting period or consult with your healthcare professional to determine the safest method.
Bottom line: Is intermittent fasting right for you?
Although intermittent fasting has become popular due to its potential benefits for metabolic health, it is not suitable for everyone. Before you begin, consider how fasting may affect your hormones, metabolism, stress levels, and blood sugar control.
Talk to your health care provider, such as a nutritionist or your doctor, about a new diet. If fasting isn’t right for you, there are endless options for nutritional plans that can help you reach your goals instead.
And if you decide to give it a try, be sure to check it out. intermittent fasting tracker Inside the MyFitnessPal app.
Frequently Asked Questions
Does intermittent fasting cause or worsen gastroesophageal reflux disease (GERD)?
Research on intermittent fasting is mixed. There is limited data showing that fasting may improve GERD symptoms. (20)
What should be your first meal when intermittent fasting?
When breaking your fast during intermittent fasting, it is important to choose a balanced diet that provides essential nutrients. It is recommended that you eat a diet based on whole foods that provide lean protein, complex carbohydrates, and healthy fats.
What can I drink for breakfast while intermittent fasting?
If you want to avoid the quick fixation on calorie-free drinks like water, black coffee or tea.
How can MyFitnessPal help you?
If you’ve already been doing intermittent fasting or are simply curious about the potential health benefits of your eating habits, MyFitnessPal’s premium intermittent fasting tracker feature can help! You can choose one of three fasting patterns depending on your lifestyle or goals.
12:12 — 12-hour fasting, 12-hour eating window. This pattern is ideal for aligning your eating with your circadian rhythm.
14:10 — 14-hour fasting, 10-hour eating window. This pattern will help you reduce your intake of regular meals and snacks throughout the day.
16:8 – 16 hours fasting, 8 hours eating period. This pattern typically involves skipping morning or afternoon meals.
You can then track your daily fasting period along with your meals, water, and exercise in your diary. Are you ready to give it a try? Start your free MyFitnessPal premium trial today.
The post What You Need to Know Before Starting Intermittent Fasting: 5 Scientific Considerations appeared first on the MyFitnessPal Blog.
