Can Crash Diets Affect Your Health?
Key takeaways:
Crash diets usually involve restricting calories and/or excluding certain foods or food groups with the goal of losing weight rapidly.
The risks of crash diets include poor nutrition, hormonal changes, and gallstones. Crash diets can also cause mood changes and patterns of unhealthy or disordered eating.
A healthy approach to weight loss involves eating a nutritious and balanced diet, practicing mindful eating, and getting regular exercise.
Table of contents
“Crash diets” are restrictive eating plans that are intended to help you lose weight very fast. These diets often involve excluding many types of foods, and therefore come with some health risks.
Below we’ll cover the difference between safe and harmful diets for weight loss, and talk about how to make sustainable changes to the way you eat as you find an approach that’s right for you.
What is a crash diet?
Crash diets are extreme eating plans. They usually require you to exclude specific foods — or entire food groups — from your diet. Crash diets can be difficult to follow, and even more difficult to stick to over time.
Discover a simple way to manage diabetes
Patients can use GoodRx to save up to 40% on OneTouch Ultra Strips.
Crash diets often:
Promise rapid results
Require a drastic reduction in the amount of calories you eat
Tell you to follow a specific eating plan that’s very different from your current diet
Exclude many different foods or food groups
Extreme diets don’t usually work in the long run. Most people end up gaining back the weight they lost.
What are the risks of a crash diet?
Crash diets are often tempting to people because they promise a quick “fix.” But they come with some serious risks to your health.
Weight gain
One of the biggest problems with crash diets is they often result in long-term weight gain. Crash diets may be effective at first, but they aren’t sustainable. So weight loss from a crash diet is almost always temporary. This is because the pounds you shed in a crash diet are mostly water and muscle loss, not fat loss.
Crash diets can also lead to dangerous weight cycling, commonly called yo-yo dieting. This is when someone loses weight quickly, then regains weight after they stop the crash diet. And the health risks associated with yo-yo dieting go well beyond weight gain. They include an increase in conditions like heart disease and diabetes.
Is fast weight loss healthy? When you lose weight quickly, you’re likely losing water and muscle, not fat. And fast weight loss can cause nutrient deficiencies and other health issues.
Health risks associated with yo-yo dieting: Yo-yo dieting often results in long-term weight gain instead of weight loss. And it can harm your health by increasing your risk of heart disease, diabetes, and depression.
Can you target fat loss? Trying to shed fat in one specific area of the body? Science says “spot fat reduction” isn’t effective. Here’s what does work.
Malnutrition
Malnutrition is when you don’t get enough macronutrients (like fat, carbohydrates, or protein) or micronutrients (vitamins and minerals) in your diet. Crash diets that involve severe calorie restriction can lead to malnutrition.
This can cause:
Poor growth and development, specifically of muscle and bone
Dehydration
Weakened immune system
Poor energy and weakness, which can lead to worse performance at work, in school, and other daily activities
Difficulty staying focused
Hormonal changes
Losing weight too fast can delay puberty or stop your period. This can affect the way your hormones work and may make it difficult to get pregnant later in life.
Mood changes
What you eat can affect your mood. Certain foods (and lack of certain foods) can increase the likelihood of depression, anxiety, and irritability. Crash diets can also make you feel tired and affect your concentration. And being focused on a crash diet can get in the way of spending time with friends and family.
On the other hand, enjoying a wide variety of nutritious foods — like healthy fats, fruits, vegetables, and whole grains — can really boost your mood. That’s because the body needs the nutrients in food to make important brain chemicals, like serotonin.
Changes to your body’s metabolism and/or hunger cues
Calorie restriction is often part of crash diets. This can cause permanent changes to how the body deals with food and responds to hunger.
Read more like this
Explore these related articles, suggested for readers like you.
For example, your brain may no longer be able to tell when you’re full. This may make it easier to overeat. In other cases, your metabolism can slow down. When this happens, your body doesn’t burn calories as quickly or efficiently. A slowing metabolism can cause weight gain and/or make it more difficult to lose weight.
Disordered eating thoughts or behaviors
Some evidence links crash diets to disordered eating and eating disorders, mental health conditions that affect your body image and relationship to food. Sometimes, crash dieting can actually be a symptom of an eating disorder. Of course, not everyone who goes on a diet has an eating disorder. But there can be some overlap.
Problems with body image
Crash dieting can cause you to feel dissatisfied or unhappy with your body and lead to low self-esteem. As a result, you may become more likely to diet even more, creating an unhealthy cycle that’s tough to break.
Gallstones
Losing weight very quickly increases your risk of developing gallstones. This can be confusing because a higher weight is associated with an increased risk of gallstones. So losing weight is generally thought to be a good thing when it comes to gallstones. But research shows that if you lose weight very quickly (more than 3.3 lbs per week) or lose a lot of weight (more than 25% of your body weight), you have a higher chance of developing gallstones.
Use of diet pills, diet supplements, or diet teas
Some crash diets recommend drinking diet teas or taking diet pills or other supplements to promote weight loss. Many of these products are available at local drugstores. But they’re not recommended, and they can be harmful to your health.
Studies have found that some of the ingredients in these supplements can cause dangerous side effects like seizures and an abnormal heart rate. And it’s also important to remember that just because a product uses the word “natural” on its packaging doesn’t mean it’s healthy.
Signs that a diet is an unhealthy crash diet
There are certain telltale signs that a diet may be unhealthy. Consider it a red flag if a diet:
Asks you to avoid an entire food group (such as carbohydrates)
Uses the words “cleanse” or “detox”
Promises quick weight loss, and/or weight loss of more than 2 lbs per week
Has an extremely low calorie limit
Tells you that a specific product — such as a pill or tea — is all you need
Doesn’t share any reliable or reputable research to support its health claims
Sounds too good or too easy to be true
Examples of unhealthy crash dieting plans
Some examples of eating plans that may be considered crash or fad diets include:
South Beach diet
Atkins diet
Liquid diets (such as SlimFast or “juice cleanse” diets)
Cabbage soup diet
The grapefruit diet
Raw food diet
Whole30
Keto diet
And remember: Unless you have a food allergy or other health condition, no foods need to be completely off limits. Crash diets create a false perception that some foods are “good” and others are “bad.” But this can be a harmful way to think about food. And it can create undue stress around food choices. It’s important to enjoy food and the way it can connect you to memories, people, and celebrations. Just make sure you’re eating a balanced diet overall, and focusing on nutritional powerhouses, like fruits, veggies, and whole grains.
How can you lose weight safely?
If weight loss is a health goal for you, there are ways to do it safely.
Ultimately, the key to healthy weight loss is to do it in a way that feels sustainable and enjoyable to you. And this usually means doing it slowly. Below are some tips to help with healthy weight loss.
Eat a nutritious and balanced diet
A balanced and nutritious diet includes a wide variety of foods. This provides your body with a range of nutrients that support healthy growth, development, and protection from disease. Instead of following crash diets, try to focus on consuming:
Plenty of fruits and vegetables
A variety of whole grains from foods like whole-wheat products, brown rice, and quinoa
Lean proteins from foods like fish, poultry, meat, soy, and beans
Healthy fats from foods like avocados, olive oil, nuts, and seeds
Plenty of water to keep you hydrated
Eating a balanced and nutritious diet also means eating enough food to meet your daily needs. Individual calorie needs vary widely from person to person depending on age, activity level, and other factors. But in general, experts recommend 1,600 to 2,400 calories per day for women, and 2,200 to 3,000 calories for men. Unnecessarily restricting your calorie intake (or restricting which foods provide those calories) can lead to some of the health issues mentioned above.
Practice mindful eating
Take time to slow down when you’re eating. This is also called mindful eating.
In mindful eating, the goal is to combine awareness with the act of eating your food. Different people will define mindful eating differently. But the key points of mindful eating include:
Not labeling foods as good or bad: Avoid lifting up certain foods and demonizing others. Instead neutralize language around food.
Listening to your appetite: This means paying attention to your hunger and fullness cues.
Eating with balance: By being tuned into your senses, you know which foods your body needs.
The sensory awareness that comes with mindful eating can ultimately help you feel more comfortable in your body. And when you truly have a nonjudgmental attitude toward food, it can be a source of joy rather than stress.
Be physically active every day
Any physical activity is better than none at all. But this doesn’t mean you need to engage in strenuous workouts. Simply moving your body in a way that feels positive to you is most important. So the best physical activity is one that you enjoy and will be excited to do day after day.
Experts recommend that adults do cardio and strength-training workouts several times a week. But how often you work out and the types of activities you do will depend on factors like your age, overall health, goals, and personal preference.
Prioritize good sleep
You may think that sleep is unrelated to weight and weight loss. But not getting enough good quality sleep is linked to tiredness, lower activity levels, and changes in how the brain makes decisions about food.
Try these tips to get a better night’s sleep (ideally at least 8 hours per night):
Stick to a regular bedtime and wake-up time.
Turn off your screens and devices at least 1 hour before bedtime.
Keep your bedroom cool and dark.
Limit caffeine from sodas, energy drinks, and coffee or tea for several hours before bedtime.
Lose weight slowly
If your primary care provider recommends that you lose weight, do so slowly. Rushing weight loss is not healthy for the body. For safe and successful weight loss, aim for a slow-and-steady loss of about 1 lb to 2 lbs per week.
Frequently asked questions
It’s unhealthy to attempt to lose 10 lbs in 3 days. Fast weight loss plans may be “successful” in the short term, but they’re temporary. In a crash diet, you lose mostly water and muscle, not fat. This makes it likely you’ll gain back the weight quickly. And crash diets usually fall short on essential nutrients, and therefore can cause health issues. If your goal is weight loss, aim to shed 1 lb to 2 lbs per week at most.
The 7-day crash diet is a structured, weeklong fad diet that focuses on a different food group each day. It’s an extreme, unsustainable crash diet that isn’t recommended. It reduces calories, cuts out entire food groups, and can negatively affect your health. Like other crash diets, the 7-day crash diet isn’t a good choice.
Yes. Sometimes, people need to follow a specific diet. You may have a food allergy or other medical condition that affects what you’re able to eat. You may have cultural or religious beliefs that may restrict some foods. But this is not the same thing as a crash diet.
Examples of different eating patterns include:
Vegetarian: This means not eating meat, fish, or poultry. But it allows for eating eggs and dairy products.
Vegan: A vegan diet means not eating any type of animal product.
Gluten-free diet: This diet avoids all grains that contain gluten. This includes wheat, barley, and rye as well as all foods made with them. This diet is usually only for people who have been diagnosed with celiac disease or an intolerance or allergy to gluten.
Allergen-free diet: This might include cutting out groups of foods that you are allergic to like nuts, milk, eggs, or soy.
The bottom line
Crash diets aren’t the answer to good health. One of the best things you can do for your health is create a healthy relationship with food. This means eating plenty of nutrient-rich foods every day and staying away from trendy “quick-fix” diets that can damage your physical and mental health. There are many things you can do to improve your health and well-being. What you eat is just one part of the journey.
Why trust our experts?
References
American Heart Association. (2024). American Heart Association recommendations for physical activity in adults and kids.
Ashtary-Larky, D., et al. (2017). Rapid weight loss vs. slow weight loss: Which is more effective on body composition and metabolic risk factors? International Journal of Endocrinology and Metabolism.
Barrea, L., et al. (2019). Nutritionist and obesity: Brief overview on efficacy, safety, and drug interactions of the main weight-loss dietary supplements. International Journal of Obesity Supplements.
BetterHealth Channel. (2023). Body image and diets.
Bourke, C. D., et al. (2016). Immune dysfunction as a cause and consequence of malnutrition. Trends in Immunology.
Centers for Disease Control and Prevention. (2024). Physical activity basics and your health.
Eunice Kennedy Shriver National Institute of Child Health and Human Development. (2017). What causes amenorrhea? National Institutes of Health.
Ferraro, Z. M., et al. (2015). Unhealthy weight control practices: Culprits and clinical recommendations. Clinical Medicine Insights. Endocrinology and Diabetes.
Firth, J., et al. (2020). Food and mood: How do diet and nutrition affect mental wellbeing? BMJ.
Greer, S. M., et al. (2013). The impact of sleep deprivation on food desire in the human brain. Nature Communications.
Joshi, S., et al. (2018). Pros and cons of some popular extreme weight-loss diets. The Indian Journal of Medical Research.
Martins, V. J. B., et al. (2011). Long-lasting effects of undernutrition. International Journal of Environmental Research and Public Health.
Memon, A. N., et al. (2020). Have our attempts to curb obesity done more harm than good? Cureus.
National Centre for Eating Disorders. (n.d.). The effects of under-eating.
National Institute of Diabetes and Digestive and Kidney Diseases. (2017). Dieting and gallstones. National Institutes of Health.
National Institute of Diabetes and Digestive and Kidney Diseases. (2020). Eating, diet, and nutrition for celiac disease. National Institutes of Health.
O’Connor, A. (2021). How food may improve your mood. The New York Times.
Penn Medicine. (2018). Want to lose weight quickly? Here are 7 reasons why crash diets probably won’t work.
Redman, L. M., et al. (2011). Caloric restriction in humans: Impact on physiological, psychological, and behavioral outcomes. Antioxidants and Redox Signaling.
Saunders, J., et al. (2010). Malnutrition: Causes and consequences. Clinical Medicine.
Shufelt, C. L., et al. (2017). Hypothalamic amenorrhea and the long-term health consequences. Seminars in Reproductive Medicine.
Soylu, O. B. (2013). Clinical findings of functional and secondary constipation in children. Iranian Journal of Pediatrics.
Stokes, C. S., et al. (2021). Excess body weight and gallstone disease. Visceral Medicine.
U.S. Department of Agriculture. (2020). Dietary guidelines for Americans 2020-2025.
