Intermittent fasting (IF) is a dietary pattern that has received widespread attention for its potential health benefits. Some IF-ers report having more energy, losing weight, and improving their metabolic health. (1) But intermittent fasting isn’t for everyone. Before you get started, there are some health considerations you may want to consider.
Some research suggests that people with certain health conditions, such as those that affect digestion or blood sugar, or at certain stages of life, should be cautious before starting intermittent fasting. (4) Let’s break down the research-backed 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 and current medications, and as always, consult your doctor. In particular, people with diabetes, kidney stones, or gastroesophageal reflux should approach fasting with caution and receive personalized 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 their function or cause negative side effects. (6) Anyone with a history of eating disorders should avoid intermittent fasting, as any type of eating plan can trigger unhealthy patterns related to food restriction and overeating. (7)
Health conditions that may make intermittent fasting a bad idea
If you are taking medications for any health condition, including heart disease, diabetes, high blood pressure, or medications such as insulin and blood thinners that may require regular food intake for proper absorption, intermittent fasting may not be right for you. (6)
Here are other health conditions that may make intermittent fasting not suitable for you:
- diabetes: Fasting can affect blood sugar levels, causing dangerous drops or unpredictable rises. (4)
- kidney stones: Fasting may affect hydration status and dietary intake, increasing the risk of stone formation.
- underweight individuals: Fasting can lead to further weight loss, so it should be done under medical supervision and with regular medical check-ups. (8)
- Eating disorder history: Fasting may lead to unhealthy eating patterns that are unsafe for people with past or current eating disorders. (7)
Effects of intermittent fasting on metabolism
One of the most widely discussed benefits of intermittent fasting is its effect on metabolism. Research shows that fasting initiates fat burning through a process called ketosis. That’s when the body burns fat for energy in the absence of carbohydrates. (1)
Additionally, intermittent fasting can improve insulin sensitivity, potentially reducing the risk of type 2 diabetes by lowering blood sugar levels and promoting better blood sugar control. (9)
However, some noteworthy studies indicate that when compared to other types of calorie-restricted diets, fasting does not result in more significant weight loss than other types of calorie-restricted eating plans. (10)
This means that if fasting isn’t right for you, any diet that works for you can still help you achieve your weight loss goals.
Another metabolic benefit is autophagy, a cell repair and regeneration process that occurs with any type of caloric restriction. (11) This process is associated with longevity and may prevent age-related diseases by clearing damaged cells. (11)
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Hormonal effects: Why fasting may be different for women
Women’s bodies are highly sensitive to changes in calorie intake, which is why intermittent fasting affects female hormones like estrogen and progesterone. (12)
Research suggests that prolonged fasting may disrupt a woman’s reproductive hormone balance, potentially leading to irregular menstrual cycles and unpleasant symptoms. (12) Importantly, women trying to conceive may wish to avoid prolonged fasting because caloric restriction can negatively impact fertility. (12)
For women who are pregnant or breastfeeding, fasting can lead to nutritional deficiencies and insufficient caloric intake, which can affect the health of both mother and baby. (13) If you are a woman in this stage of life, talk to your healthcare team before trying intermittent fasting.
Even outside of pregnancy, women with hormonal imbalances such as polycystic ovary syndrome (PCOS) should be cautious about fasting. It may worsen symptoms. (13)
Ultimately, some research suggests that women may benefit from shorter fasting periods, such as 12 to 14 hours, rather than a stricter 16-hour schedule. (14)
About the experts:
Caroline Thomason is a nutritionist and diabetes educator who combines her love of nutrition with the power of making better health accessible. She has 12 years of experience in the industry, has been published in over 40 publications, is a CPG consultant and advisor, speaker, radio speaker and recipe developer.
Joanna Gregg, RD Is the food information manager for 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 also affects cortisol levels, a hormone responsible for managing the body’s stress response. (15)
Prolonged fasting can increase cortisol production, especially if you’re already stressed or sleep-deprived. (15) Elevated cortisol levels appear to be associated with weight gain, particularly in the abdominal region, which may counteract the weight loss effects of fasting. (16)
What’s more, once your fasting window is over, high cortisol levels may cause you to stress eat, creating a cycle of overeating and restrictive fasting. (17) This is a form of eating disorder, and if you find yourself falling into this pattern, fasting may not be right for you. (17)
Overall, if you’re prone to stress or have trouble controlling stress-related cravings, intermittent fasting may not be the best approach.
Blood sugar sensitivity: Who should be careful?
If you have blood sugar problems, such as diabetes or hypoglycemia, you need to be especially careful with intermittent fasting. (4) While fasting may improve insulin sensitivity, it may be risky for people with diabetes, as prolonged fasting can lead to dangerously low blood sugar levels. (9)
Especially if you take insulin or other medications that affect blood sugar, fasting may increase your risk of hypoglycemia, which can lead to serious symptoms such as dizziness, brain fog, confusion, or fainting. (18)
Even in people without diabetes, fasting for long periods of time can cause blood sugar to drop, leading to irritability or a general feeling of fatigue. (19) If you have a blood sugar-related condition, consider shortening your fast or consult a health care professional to find the safest approach.
Bottom line: Is intermittent fasting right for you?
While intermittent fasting has become popular for its potential benefits for metabolic health, it isn’t suitable for everyone. Before you begin, consider how fasting may affect your hormones, metabolism, stress levels, and blood sugar regulation.
As with any new eating habits, consult a health care provider such as a nutritionist or doctor. If fasting isn’t for you, there are countless options for your nutrition plan to help you achieve your goals.
If you decide to give it a try, be sure to check out the intermittent fasting tracker within the MyFitnessPal app.
FAQ
Can intermittent fasting cause or worsen gastroesophageal reflux disease (GERD)?
Research on intermittent fasting is mixed. There is some limited data to suggest that fasting may improve gastroesophageal reflux symptoms. (20)
What should I eat as my first meal while intermittent fasting?
When breaking your fast during intermittent fasting, it is important to choose a balanced diet that provides essential nutrients. Meals based on whole foods that provide lean protein, complex carbohydrates, and healthy fats are a good choice.
What can you drink in the morning during intermittent fasting?
If you want to avoid breaking your fast, stick to non-calorie drinks like water, black coffee, or tea.
How MyFitnessPal can help
Whether you’ve already started intermittent fasting or are just curious about the potential health benefits of this eating pattern, MyFitnessPal’s advanced intermittent fasting tracker feature can help! You can choose one of 3 fasting modes based on your lifestyle or goals:
12:12 — 12 hours fasting, 12 hours eating window. This mode is great for synchronizing meals with your circadian rhythm.
14:10 — 14 hours fasting, 10 hours eating window. This model encourages regular meals throughout the day and reduces snacking.
16:8 – 16 hours fasting, 8 hours eating window. This pattern usually involves skipping the morning or afternoon eating period.
You can then record your daily fasting times in your diary, as well as your diet, water, and exercise. Ready to give it a try? Start your free trial of MyFitnessPal Premium today.
The post What You Need to Know Before Starting Intermittent Fasting: 5 Scientific Considerations appeared first on MyFitnessPal Blog.