Fasting is not a universal solution, as it can cause serious issues in people with underlying health conditions.
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Intermittent fasting is popular for weight loss and improving metabolic health, but it’s not safe for everyone. People with eating disorders, pregnant or breastfeeding women, children, frail seniors, diabetics, underweight individuals, and those on certain medications face real risks. Experts stress fasting is a tool, not a universal solution, and medical guidance is essential before trying it.
Social media sites are riddled with before and after pictures of individuals who claim that intermittent fasting helped transform their physiques. And truth be told, there have been numerous scientific studies which support some of its positive effects, such as improved glucose levels and weight loss. However, there’s one thing missing in these influencer posts.
For some people, it doesn't just not help, it can actually do damage.
Intermittent fasting essentially involves eating during a certain number of hours and fasting the remaining hours of the day.
One of the most popular versions is the 16: 8 method, fast for 16 hours and eat 8. Easy, right? However, the response of the body to fasting is not the same in all people.
It actually varies depending on their health conditions and stages in life. What is perfect for a healthy adult in their thirties can be dangerous for someone on medication for diabetes or the still-growing teenager.
Before you get into the trend, here's who must really avoid it.
This group is the most important group, yet the least spoken about in the wellness sector. If you fall into the category of those diagnosed with anorexia, bulimia, binge eating disorder, or any disordered eating, definitely don’t try intermittent fasting.
A study published in BMC Clinical Diabetes and Endocrinology has cautioned against the recommendation for people with an eating disorder, or even someone with a history of disordered eating, to take up intermittent fasting.1
Furthermore, adolescents and young adults should be approached with extreme caution, particularly those who identify as female or gender diverse.
The reason for this is that intermittent fasting involves intentionally ignoring hunger signals and restricting foods to specific windows. A person who has previously struggled with controlling or punishing their relationship with food can find that structure quickly slide into eating in ways that are harmful to them. The evidence is clear that fasting can instigate the restriction-binge cycle in vulnerable persons – and with it, dangers.
Maternity and breastfeeding are demanding in terms of nutrition. The body requires a constant and consistent supply of calories, protein, vitamins and minerals throughout the day.
Any fasting, even for a few hours stops this supply in ways that can affect the mother and child.
A publication in Frontiers in Nutrition has noted that some types of intermittent fasting in pregnant women are linked to negative health outcomes for mothers and offspring, resulting in fatigue, dehydration, and a possible impact on the fetus.
The availability of calories has been linked to the milk supply and quality of lactating women. Intermittent fasting may impact reproductive hormones, according to animal studies on women trying to conceive. It's written in black and white, according to dietitians and medical professionals, you shouldn't fast during pregnancy and lactation.
Type 1 diabetes is when the pancreas makes little or no insulin. Blood sugar is controlled by injecting insulin from outside the body. When we fast, blood sugar will drop.
When people take insulin medication, that drop can become dangerously severe hypoglycemia, which can cause dizziness, confusion, fits and in some cases, loss of consciousness.2
The message from medical experts is quite clear - Type 1 diabetes patients should not fast. The American Diabetes Association does not recommend intermittent fasting as a treatment for diabetes.
Even in people with type 2 diabetes taking insulin, fasting poses a real risk of hypoglycemia and should only be attempted with medical supervision and an adjustment of medications beforehand.
Kids and teens are in stages of active growth. Children require constant nourishment throughout the day to support their bones, brains, hormones, and growth. Caloric restriction affects the recovery from them, even time-restricted eating.
Researchers have explicitly stated that children and elderly individuals should not participate in intermittent fasting due to the lack of research on safety and efficacy in these populations. 3
Beyond the nutritional angle, there is also the eating disorder risk. Teenagers, especially young women, are among the most vulnerable demographic for developing disordered eating. Introducing a structured food restriction protocol at this life stage, particularly one that is heavily glamorized on social media, is a risk that no wellness benefit justifies.
As people get older their ability to maintain muscle strength decreases. It is essential to consume sufficient protein and calorie intake.
The elderly people who have frailty should not skip their main meals because doing so will lead them to the two conditions of malnutrition and muscle loss, which decrease their quality of life in senior years.
This one catches many people off guard. Intermittent fasting doesn't just affect what you eat, it affects when and how medications work in the body. Several drugs are required to be taken with food, and some actively interact with fasting in dangerous ways.
Blood pressure medications, certain cholesterol drugs, and some mental health medications can all cause problems when taken while fasting, including dizziness, dangerous drops in blood pressure, or reduced efficacy.
Fasting increases the chances that blood levels of electrolytes may get dangerously low in people who take blood pressure or heart disease medications. 4
Anyone on regular prescription medication should speak to their doctor before trying any fasting protocol, and this is not optional advice.
Intermittent fasting serves as the primary method for weight reduction. The solution to this problem exists because they already maintain an underweight status.
The practice of maintaining eating times between two specific intervals creates difficulties, which makes it hard for people to reach their required calorie intake because of their limited ability to eat and their inability to control their hunger.
Underweight individuals already face risks of weakened immunity, bone density loss, hormonal disruption, and poor wound healing.
This creates additional weight loss dangers, which become more severe.
Such people need to focus on complete food consumption because they should not face limitations on when they can eat.
A 2024 analysis of over 20,000 adults presented at the American Heart Association's Scientific Sessions found that people who limited their eating to less than 8 hours per day were more likely to die from cardiovascular disease compared to those who ate across a 12 to 16-hour window.5
The findings showed danger to people who had heart conditions, which already existed because further research needed to be conducted on the preliminary results.
None of this means intermittent fasting is inherently dangerous . For healthy adults without the conditions listed above, the evidence for its benefits remains solid.
But the wellness industry has a habit of flattening nuance in favor of trends. Intermittent fasting is not a universal prescription. It is a dietary tool, and like all tools, it causes damage when applied to the wrong situation.
If you fall into any of the groups above, the conversation to have is with your doctor or a registered dietitian, not your Instagram feed.
Why should people with a history of eating disorders avoid intermittent fasting?
Intermittent fasting involves restricting eating windows and ignoring hunger signals, which can trigger harmful eating patterns such as the restriction-binge cycle in individuals with a history of eating disorders like anorexia or bulimia. Studies caution against recommending fasting to this vulnerable group as it may worsen their relationship with food and lead to health risks.
Is intermittent fasting safe for pregnant or breastfeeding women?
No, pregnant and breastfeeding women should avoid intermittent fasting. Adequate and consistent nutrition is crucial during these stages to support both mother and child. Research indicates fasting during pregnancy can cause fatigue, dehydration, and negatively affect fetal development and milk quality, making it unsafe for these groups.
Can people with type 1 diabetes try intermittent fasting safely?
People with type 1 diabetes should not practice intermittent fasting as it can lead to dangerously low blood sugar (hypoglycemia). Since type 1 diabetes requires external insulin, fasting can cause severe drops in glucose levels, increasing risks of dizziness, confusion, seizures, and loss of consciousness.
What are the risks of intermittent fasting for older adults, especially those who are frail?
Older adults, particularly frail individuals, risk malnutrition and muscle loss from intermittent fasting due to insufficient calorie and protein intake during fasting periods. Maintaining muscle mass and adequate nutrition is vital to their quality of life, so fasting protocols that restrict eating times may be harmful.
How can intermittent fasting affect people taking prescription medications?
Fasting alters the timing and effectiveness of some medications. Drugs such as blood pressure medications, cholesterol treatments, and mental health prescriptions may cause dizziness, dangerous drops in blood pressure, or reduced efficacy when taken without food. People on medications should consult their doctor before attempting intermittent fasting.
References:
1. National Library of Medicine | Intermittent fasting: consider the risks of disordered eating for your patient
2. National Library of Medicine | Effect of intermittent fasting on diabetic patients-A narrative review
3. National Library of Medicine | Intermittent fasting and immune aging
4. Bastyr University | 5 Times You Should Avoid Intermittent Fasting
5. Newsroom.heart.org | 8-hour time-restricted eating linked to a 91% higher risk of cardiovascular death
Disclaimer: This content is for general informational purposes only and should not replace professional medical advice. Always consult a qualified healthcare provider with any questions about your health or treatment options.
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