Fasting, an age-old practice of restricting food intake, has seen a resurgence in popularity, particularly water fasting. This article delves into the 19-day water fasting challenge, exploring its potential benefits and associated risks, while considering its suitability for different individuals. Water fasting, which involves consuming nothing but water, has gained traction as a quick weight loss method and for its purported health benefits.
What is Water Fasting?
Water fasting is a type of fast where you consume nothing besides water. Most water fasts typically last for 24-72 hours, and it's generally not recommended to extend this period without medical supervision due to potential health risks. Some individuals undertake water fasting for religious or spiritual reasons, while others aim to lose weight, "detox," or reap specific health benefits, or even in preparation for a medical procedure. Popular diets, such as the lemon detox cleanse, are modeled after the water fast, allowing only a mixture of lemon juice, water, maple syrup, and cayenne pepper for up to 7 days.
How to Approach a Water Fast
Currently, there aren't any established scientific guidelines for initiating a water fast. However, it is advisable to prepare your body for the absence of food over 3-4 days if you're new to water fasting. This preparation can involve reducing portion sizes at each meal or fasting for a portion of the day.
During the Water Fast (24-72 Hours)
During this phase, you are restricted to consuming only water. Due to potential health risks, it's crucial to avoid extending the water fast beyond 72 hours without medical supervision. Some individuals may experience weakness or dizziness during this period, necessitating caution when operating heavy machinery or driving to prevent accidents.
Post-Fast (1-3 Days)
After completing the water fast, resisting the urge to consume a large meal is important. A large meal post-fast can trigger uncomfortable symptoms. Instead, it's recommended to break the fast with a smoothie or smaller meals. As you feel more comfortable, you can gradually reintroduce larger meals throughout the day. The post-fast phase is particularly crucial after longer fasts to mitigate the risk of refeeding syndrome, a potentially fatal condition characterized by rapid shifts in fluid and electrolyte levels. While this phase typically lasts a day, individuals fasting for 3 or more days may require up to 3 days to comfortably resume larger meals.
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Potential Benefits of Water Fasting
Both human and animal studies have associated water fasting with several potential health benefits.
Autophagy Promotion
Autophagy is a process where old or damaged cell parts are broken down and recycled. Animal studies suggest that autophagy may offer protection against diseases like cancer, Alzheimer's, and heart disease. For instance, autophagy can prevent the accumulation of damaged cell components, which is a risk factor for various cancers, potentially hindering cancer cell growth. Animal studies have consistently demonstrated that water fasting aids in promoting autophagy and may extend lifespan. However, human studies on water fasting, autophagy, and disease prevention remain limited, necessitating further research before it can be recommended to promote autophagy.
Blood Pressure Reduction
Research indicates that longer, medically supervised water fasts can help individuals with high blood pressure lower their blood pressure. One study involving 48 overweight or obese participants found that water fasting for an average of 17 days under medical supervision led to reductions in systolic blood pressure and improvements in LDL (bad) cholesterol and inflammation levels. Similarly, another review concluded that water fasting could significantly reduce blood pressure levels and body weight in individuals with hypertension. Nonetheless, more research is warranted to assess the relationship between short-term water fasts (24-72 hours) and blood pressure.
Enhanced Insulin and Leptin Sensitivity
Insulin and leptin are essential hormones that influence metabolism. Insulin aids the body in storing nutrients from the bloodstream, while leptin promotes feelings of fullness. Research suggests that water fasting may enhance the body's sensitivity to leptin and insulin, thereby increasing their effectiveness. Greater insulin sensitivity means that the body becomes more efficient at reducing blood sugar levels. Enhanced leptin sensitivity can improve the processing of hunger signals, reducing the risk of obesity.
Reduced Risk of Chronic Diseases
Some evidence suggests that water fasting may lower risk factors associated with chronic diseases like diabetes, cancer, and heart disease. A 2013 study involving 30 healthy adults who underwent a 24-hour water fast revealed significantly lower blood levels of triglycerides, a risk factor for heart disease, post-fast. Some research also indicates that water fasting may protect the heart against damage from free radicals, unstable molecules that can damage cell components and play a role in many chronic diseases. Moreover, studies in animals and humans have found that water fasting may suppress genes that promote cancer cell growth and improve the effects of chemotherapy. However, it's important to note that only a limited number of studies have analyzed the effects of water fasting in humans, emphasizing the need for more human research before making definitive recommendations.
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Potential Risks and Dangers of Water Fasting
Despite potential benefits, water fasting carries health risks.
Loss of the Wrong Type of Weight
Initially, much of the weight loss may come from water, carbohydrates, and even muscle mass.
Dehydration
Paradoxically, a water fast can lead to dehydration. Approximately 20-30% of daily water intake comes from food. If you're drinking the same amount of water but not consuming food, you might not be adequately hydrated. Symptoms of dehydration include dizziness, nausea, headaches, constipation, low blood pressure, and reduced productivity. To avoid dehydration, it may be necessary to increase water intake.
Orthostatic Hypotension
Orthostatic hypotension, a drop in blood pressure upon standing, can cause dizziness, lightheadedness, and fainting. If experienced during fasting, it may be necessary to avoid driving or operating heavy machinery due to the risk of accidents. If these symptoms occur during a water fast, it may not be a suitable option.
Worsening of Medical Conditions
Water fasting may exacerbate certain medical conditions. Individuals with the following conditions should consult a healthcare professional before attempting a water fast:
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- Gout: Water fasting may increase uric acid production, a risk factor for gout attacks.
- Eating disorders: Fasting may encourage disordered eating behaviors in some individuals.
Water Fasting and Weight Loss
Like other forms of fasting, water fasting can aid in weight loss. However, alternative approaches like intermittent fasting and alternate-day fasting may be more effective for weight loss with fewer risks. These fasts offer similar health benefits but can be followed for extended periods, as they allow food consumption, reducing the risk of nutrient deficiencies.
Prolonged Fasting: A Deeper Dive
Prolonged fasting, characterized by minimal or no food or caloric beverages for several days to weeks, includes water-only fasting and Buchinger fasting. Water-only fasting involves consuming 2-3 liters of mineral or distilled water daily without food. Buchinger fasting, medically supervised, allows small amounts of food daily, totaling 200-300 kcal and 25-35 g of carbohydrates.
Metabolic Switch
The mechanism behind the benefits involves a metabolic switch. After 12 to 36 hours of fasting, the body shifts from using glucose to fatty acids and ketones for energy. Adipocytes release free fatty acids, converted into ketones by the liver. Ketone levels plateau after 5-10 days, serving as the primary energy source and providing physiological benefits.
Impact on Metabolic Health
Prolonged fasting's effects on metabolic health measures, including body weight, blood pressure, plasma lipids, and glycemic control, have been studied. Research reveals that prolonged fasting for 5-20 days increases circulating ketones and causes mild to moderate weight loss (2-10%). However, approximately two-thirds of the weight lost is lean mass, raising concerns about muscle protein breakdown. Systolic and diastolic blood pressure consistently decrease, but the impact on plasma lipids is less clear, with some trials showing decreases in LDL cholesterol and triglycerides, while others show no benefit. In individuals with normal glucose levels, reductions in fasting glucose, fasting insulin, insulin resistance, and glycated hemoglobin (HbA1c) were observed. However, these factors remained unchanged in patients with type 1 or type 2 diabetes.
Refeeding Effects
The effects of refeeding were examined in a few trials, revealing that metabolic benefits were no longer observed 3-4 months after the fast, even with maintained weight loss. Adverse events, including metabolic acidosis, headaches, insomnia, and hunger, were noted in some studies.
Prolonged Fasting vs. Intermittent Fasting
Intermittent fasting, with short periods of food abstention (16 to 36 hours), is a popular form of fasting. Prolonged fasting appears to be a moderately safe diet therapy for clinically significant weight loss (>5%) over a few days or weeks.
10-Day Complete Fasting Study: Effects on Metabolic Homeostasis
A study investigated the safety and time effects of metabolic homeostasis and health indexes during prolonged fasting. Thirteen participants underwent a 10-day complete fast (CF) under medical supervision, including a 3-day baseline (BL), 10-day CF, 4-day calorie restriction (CR), and 5-day full recovery (FR). Body healthy status was assessed by surveying pulse, blood pressure, body weight (BW), blood glucose and ketones, body composition, and nutritional and biochemistry indexes at different times.
Key Findings
BW declined about 7.28 kg (-9.8%) after 10-day CF, accompanied by increased pulse and decreased systolic blood pressure, but there were no changes to the myocardial enzymogram. Body composition analysis showed fat mass was constantly lost, but lean mass could recover after CR. The energy substrate switch from glucose to ketone occurred and formed a stable dynamic balance between 3-6 days of CF. The lipid metabolism presented increased total cholesterol, LDL-C, ApoA1, and almost no changes to TG and HDL-C. Prolonged CF did not influence liver function, but induced a slight decrease of kidney function. The interesting results came from the marked increase of lipid-soluble vitamins and a significant decrease of sodium and chlorine.
Conclusion of the Study
Adults could well tolerate a 10-day CF, and a new metabolic homeostasis was achieved. The study suggests that no vitamins but NaCl supplement should be considered.
Who Should Avoid Water Fasting?
Water fasting is not safe for everyone. The following individuals should either avoid fasting or only do so under medical supervision:
- Children and adolescents
- Adults over the age of 75
- People who are pregnant or nursing
- Individuals with an eating disorder
- Those who are underweight
- Those with a heart condition or issues with their heart
- Those with type 1 diabetes
- Those who have uncontrolled migraines
- Those who are undergoing a blood transfusion
- Those who are taking medications
Guidelines During and After Fasting
During fasting, it is recommended to consume 2-3 liters of water daily, especially mineralized water, to replace essential minerals lost during fasting. Most types of fasting should not last for more than 24 hours. Anyone who would like to fast for longer should discuss the risks and benefits with a healthcare professional. Healthcare professionals may recommend avoiding strenuous and highly physical activities during fasting. Experts recommend reintroducing food in small increments after fasting and preparing one’s body for this by practicing it before beginning fasting. This can include dividing food intake into five smaller meals a day: breakfast, lunch, dinner, and two snacks. They also recommend that a person avoid processed foods before and after fasting. Some say that following a Mediterranean diet can help. This includes eating a diet of whole grains, fresh fruits and vegetables, legumes, and nuts. It also typically includes lean proteins, such as fish, over red meat. Following fasting, especially longer-term fasting, it is important to introduce food to the body slowly to prevent developing refeeding syndrome. This serious condition occurs when there are medical complications due to rapid changes in fluid and electrolyte levels. Fasting deprives the body of the fuel it needs, so expect to feel tired and low on energy. A lack of food can also make people feel dizzy, weak, or nauseous, and if these symptoms are particularly bad, it is important to eat something. It is also important to drink enough water to prevent dehydration. Getting plenty of rest, sitting down, and avoiding intense exercise can help to conserve energy. It is natural to feel irritable or tired from a lack of food. However, if someone begins to feel disoriented or confused while fasting, they should seek medical advice.
Alternate-Day Fasting
Alternate-day fasting (ADF) is a restrictive type of intermittent fasting that is often used for weight loss. Alternate-day fasting, as the name suggests, involves fasting every other day. When you fast, your body starts to burn stored fat for energy, a process known as lipolysis. When done correctly, ADF can also give you the benefits of fasting beyond weight loss. However, most people will find fasting every alternate day challenging.
Potential Benefits of Alternate-Day Fasting
Alternate-day fasting may be able to improve cardiometabolic health, encourage cell repair, reduce inflammation, and improve longevity. It enables autophagy, which is an internal housekeeping process that your body uses to repair or dispose of damaged cells and molecules. Within four weeks of practicing alternate-day fasting, participants had higher levels of beta-hydroxybutyrate in their blood. Alternate-day fasting can be an effective way to achieve weight loss. However, weight loss depends on various factors. For instance, making sure you exercise while you're following this fasting regimen can help you preserve muscle mass while losing fat.
Other Side Effects of Fasting
Other side effects of fasting include fatigue, hunger, low mood, irritability, difficulty concentrating, food-related thoughts, and fear of losing control and overeating on non-fasting days.
Alternative Fasting Methods
- 5:2 fasting: Instead of fasting every alternate day, 5:2 fasting involves eating normally for five days a week and fasting twice a week. On fasting days, you consume 25% of your normal calorie intake.
- 18:6 fasting: 18:6 fasting is a form of time-restricted eating that involves fasting for 18 hours a day and eating within a six-hour window.
- 12-hour fast: 12-hour fasting is another form of time-restricted eating that involves fasting for 12 hours and feeding for 12 hours. This is one of the easiest forms of intermittent fasting to practice since you're likely to be sleeping for six to eight hours of the fasting period.
Intermittent Fasting
Over the last several years, intermittent fasting has become increasingly popular for its promises of improved health and weight control. Proponents claim that extended fasting periods promote cellular repair, improve insulin sensitivity, increase levels of human growth hormone, and alter gene expression in a way that promotes longevity and disease protection.
Potential Side Effects of Intermittent Fasting
- Intermittent fasting may make you feel sick.
- It may cause you to overeat.
- Intermittent fasting may cause older adults to lose too much weight.
- It may be dangerous if you're taking certain medications.