Is it okay to not eat once a week? The health benefits and risks of 24-hour intermittent fasting

October 7, 2025 •

6 min read

According to a 2022 review of 43 studies, intermittent fasting can lead to significant reductions in body weight and fat mass. This has prompted many to ask, "Is it okay to not eat once a week?" as a strategy for weight management and metabolic health, but it's important to understand the full picture before adopting such a practice.

Quick Summary

This article examines the practice of not eating for 24 hours once a week, known as the Eat-Stop-Eat method. It covers the potential health benefits, such as weight loss and improved metabolic markers, along with important risks and side effects.

Key Points

For healthy adults, weekly 24-hour fasting is a safe form of intermittent fasting. It is often called the 'Eat-Stop-Eat' method and can be performed once or twice a week.
Weekly fasting offers metabolic benefits and can aid in weight loss. It promotes metabolic switching from using sugar to burning fat for energy, which helps with weight and fat reduction.
Potential benefits include improved insulin sensitivity, heart health, and cellular repair. Regular fasting can lower blood pressure and cholesterol, reduce inflammation, and trigger autophagy, a cellular cleaning process.
Common side effects include hunger, headaches, and fatigue. These are most common during the initial adjustment period and can be managed by staying well-hydrated.
Certain groups should avoid fasting. Pregnant or breastfeeding women, individuals with eating disorders, and people with type 1 diabetes should not fast.
Safe fasting requires proper planning and nutrition. On eating days, focus on nutrient-dense foods. On fasting days, drink plenty of water and avoid strenuous exercise.
Other sustainable alternatives exist. Calorie-controlled diets, mindful eating, and regular exercise can also achieve significant health benefits without a strict fasting schedule.

Understanding the 24-Hour Fast

Intermittent fasting, or IF, is an eating pattern that cycles between periods of eating and fasting. A 24-hour fast performed once a week is one of the more structured forms, often called the "Eat-Stop-Eat" method. For example, one might choose to fast from dinner on Monday until dinner on Tuesday. During the fasting period, only calorie-free beverages like water, black coffee, and unsweetened tea are consumed. On non-fasting days, a person eats normally, focusing on a healthy, balanced diet.

The physiological process behind this method is known as "metabolic switching". After about 12 to 14 hours without food, the body depletes its stores of glucose (sugar) and begins to break down stored fat for energy. This process is called ketosis and is a key mechanism behind many of the health benefits associated with fasting. Regular, brief periods without food are believed to prompt this metabolic shift, which is different from the prolonged and dangerous state of starvation mode.

The potential health benefits

For healthy adults, incorporating a weekly 24-hour fast can offer several science-backed advantages:

Weight loss and fat reduction: By limiting total calorie intake over the week, a 24-hour fast can effectively lead to weight loss. Studies have shown it can be as effective as traditional calorie-restricted diets for shedding pounds. In particular, fasting may lead to greater reductions in body fat and belly fat compared to continuous calorie restriction.
Improved metabolic health: Regular fasting has been linked to improvements in insulin sensitivity and blood sugar management. This can help lower the risk factors for type 2 diabetes and metabolic syndrome by allowing the body to transport glucose more efficiently.
Enhanced heart health: Research indicates that intermittent fasting can improve blood pressure, lower levels of LDL (bad) cholesterol, and reduce triglycerides. These improvements can collectively contribute to a lower risk of heart disease.
Cellular repair and detoxification: Fasting triggers a process known as autophagy, where cells clean out and recycle old, damaged components. This cellular renewal is linked to a variety of health benefits, including better immune function and potentially a longer lifespan.
Reduction in inflammation: Some studies have found that intermittent fasting can decrease markers of inflammation in the body. Chronic inflammation is a driver of many diseases, so reducing it is beneficial for long-term health.

The risks and side effects of weekly fasting

While weekly 24-hour fasting can be beneficial, it is not without its risks and side effects. For many, the initial adjustment period can be challenging, both physically and mentally.

Common side effects

Hunger and cravings: The most immediate and obvious side effect is intense hunger, especially in the early stages. Some people may also experience heightened cravings for unhealthy foods.
Headaches and fatigue: Fasting headaches are common and may be caused by dehydration, caffeine withdrawal, or low blood sugar. Fatigue and irritability are also frequent, as the body adjusts to using fat for fuel instead of glucose.
Dehydration: It is crucial to drink plenty of water and calorie-free fluids during a fast, as the body loses fluids and electrolytes when food intake is stopped. Dehydration can exacerbate other side effects like fatigue and dizziness.
Potential malnutrition: If a person does not consume a healthy, nutrient-dense diet on their eating days, there is a risk of nutrient deficiencies. The goal is not just to eat less, but to eat well.
Risk of overeating: Some individuals may feel the urge to binge or overeat after a fast, undoing the potential benefits of the calorie restriction. It is essential to break the fast gently and mindfully.

Who should avoid fasting?

Certain individuals should avoid fasting entirely or only do so under strict medical supervision:

Pregnant or breastfeeding women: Nutritional needs are higher during these periods.
Individuals with a history of eating disorders: Fasting can be a trigger for disordered eating behaviors.
People with type 1 diabetes: The risk of hypoglycemia is significant, and fasting requires careful management of insulin and blood sugar.
Children and adolescents: Young people need consistent nutrition for growth and development.
People on medication: Some medications must be taken with food, and fasting could interfere with their effectiveness.

Alternative intermittent fasting methods

If weekly 24-hour fasting seems too challenging or is not suitable, other forms of intermittent fasting may be more sustainable. Each method offers different pros and cons, which can be tailored to individual lifestyles and goals.


Method	Frequency	What to Eat/Drink	Potential Benefits	Potential Drawbacks	Sustainability
Weekly 24-Hour Fast (Eat-Stop-Eat)	Once or twice per week	Water, black coffee, unsweetened tea	Significant weekly calorie reduction, triggers autophagy	Strong hunger, fatigue, irritability, risk of malnutrition if not careful	Challenging for beginners; may not be sustainable long-term
16:8 Time-Restricted Eating	Daily	All meals and snacks within an 8-hour window	Convenient, easier to maintain, aligns with circadian rhythm	May cause headaches initially, can interfere with social events	Higher sustainability; good for beginners
5:2 Method	Two non-consecutive days per week	500-600 calories on fasting days, normal diet otherwise	Flexibility on fasting days, moderate calorie reduction	May still cause hunger and low energy on fast days, can be difficult to count calories	Moderate sustainability; allows for some food on fast days

How to practice weekly fasting safely

For those who are healthy and cleared by a doctor, the Eat-Stop-Eat method can be safely integrated with proper planning. Here are some guidelines for a safe and effective fast:

Stay hydrated: Drink plenty of water throughout the fasting period. This can help manage hunger and prevent dehydration, which is a common cause of headaches and fatigue.
Plan your eating days: Focus on a balanced, nutritious diet with plenty of fiber, protein, healthy fats, and micronutrients. Avoid overcompensating with high-calorie junk food on non-fasting days, as this will negate the benefits.
Ease into it: Don't jump into a full 24-hour fast. Consider starting with shorter time-restricted eating periods, like 12 or 16 hours, to let your body adjust.
Listen to your body: Pay attention to how you feel. If you experience severe dizziness, confusion, or other concerning symptoms, end the fast immediately.
Modify exercise: Avoid intense workouts on your fasting day. Light exercise like walking or yoga is acceptable, but strenuous activity should be reserved for your eating days when your body has fuel.
Mindful refeeding: When breaking your fast, eat a small, balanced meal rather than a large, heavy one. A big meal after a prolonged fast can cause digestive discomfort.

Beyond fasting: other ways to improve nutrition

Fasting is just one tool in the nutritional toolbox. Many people can achieve similar health benefits through consistent, non-fasting dietary and lifestyle changes. These include:

Calorie-controlled diets: Creating a modest calorie deficit every day is a proven way to achieve gradual, sustainable weight loss.
Focusing on whole foods: Prioritizing a diet rich in fruits, vegetables, whole grains, and lean proteins ensures you get the necessary vitamins and minerals.
Increasing fiber and protein intake: High-fiber and high-protein foods increase satiety, helping you feel full for longer and naturally reducing overall calorie consumption.
Regular exercise: Combining regular physical activity, including both aerobic and strength training, with a healthy diet is a powerful strategy for weight management and overall health.

Conclusion

In summary, is it okay to not eat once a week? For most healthy adults, a weekly 24-hour fast is a relatively safe form of intermittent fasting that can offer metabolic benefits like weight loss, improved heart health, and cellular repair. However, it is not a universally suitable practice and comes with potential side effects such as hunger, headaches, and fatigue. Importantly, individuals with certain health conditions, pregnant women, and those with a history of eating disorders should avoid it. Before beginning any fasting regimen, it's crucial to consult with a healthcare provider to ensure it aligns with your specific health needs and goals. Many people may find that focusing on a balanced, nutritious diet and consistent exercise offers a more sustainable and less strenuous path to improving health.

For more evidence-based information on intermittent fasting, visit the Johns Hopkins Medicine page on the subject: Intermittent Fasting: What is it, and how does it work?.

Frequently Asked Questions

When you fast for 24 hours, your body first uses up its stored glucose for energy. After about 12 to 14 hours, it switches to burning stored fat in a process called ketosis. This can lead to weight loss and other metabolic benefits.

For most healthy adults, fasting for one day a week is generally safe. However, people with certain medical conditions, pregnant or breastfeeding women, and those with a history of eating disorders should avoid it and consult a doctor first.

On a fasting day, it is crucial to stay hydrated by drinking plenty of water, black coffee, or unsweetened tea. You should also listen to your body and avoid intense physical activity.

Common side effects include feelings of hunger, headaches, fatigue, and irritability. These symptoms often decrease over time as your body adjusts.

Short-term fasting, such as a 24-hour fast once a week, is not typically associated with significant muscle loss. The body primarily burns fat for fuel during this period. Long-term, prolonged fasting, however, can lead to muscle breakdown.

You should break your fast gently with a small, balanced meal rather than a large, heavy one. A meal with lean protein, healthy fats, and vegetables is a good choice to avoid digestive discomfort.

Alternatives include less intense intermittent fasting methods, like the 16:8 plan, or focusing on other sustainable healthy habits. This can involve increasing protein and fiber, eating mindfully, and exercising regularly.