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August 28, 2024

How Long Should You Do Water Fasting (Water Diet)?

What is Water Fasting?
Different Types of Water Fasting
Claimed Benefits vs. Evidence
Risks of Water Fasting
Tips and Alternatives
Healthy Meal Prep London

Water fasting - sometimes called the water diet or the water detox diet - is often promoted online as a quick fix for weight loss or detoxification. It typically involves consuming only water or extremely limited calories for one or more days. While the idea may sound appealing in its simplicity, water fasting is not supported by strong scientific evidence and is not recommended for health or weight management.

Despite widespread claims, abstaining from food does not enhance detoxification, accelerate sustainable fat loss, or “reset” the body. Instead, it places unnecessary stress on physiological systems that rely on a regular supply of energy and nutrients to function optimally.

What Is Water Fasting?

A water fasting diet generally refers to intentionally abstaining from food while consuming only water for a set period, ranging from 24 hours to several days. It’s often framed as a way to “reset” the body, eliminate toxins, or accelerate fat loss.

However, from a physiological standpoint, the body does not require food deprivation to detoxify. The liver, kidneys, lungs, and gut already perform this function continuously. Removing food does not enhance detoxification - it simply removes essential nutrients.

Different Types of Water Fasting (and Why They’re Still Problematic)

Water-only Fasting

This is the most extreme version, involving zero food intake. While short-term weight loss may occur, it is largely due to loss of water and glycogen, not body fat. This approach significantly increases the risk of fatigue, dizziness, electrolyte imbalance, and nutrient deficiency - particularly if extended beyond 24 hours.

High-Water Foods Mislabelled as Fasting

Water fasting is sometimes incorrectly grouped with diets based on fruits and vegetables. While these foods are hydrating, this approach is not fasting and is far safer because it provides carbohydrates, fibre, vitamins, and minerals. Even so, it can still be nutritionally incomplete if followed for too long, and we would not actively recommend pursuing such a diet.

Fluid-Only or “Detox” Drinks

Some versions allow herbal teas or flavoured waters but still exclude food entirely. Despite claims, these drinks do not cleanse toxins and deprive the gut of fibre and energy, which can impair digestion, blood sugar regulation, and mood.

Dates and Water Diet

The dates and water diet involves eating solely dates (21 per day to be precise) and water for a given period. This is highly restrictive and lacks protein, fats, as well as key micronutrients. While dates provide energy, this approach does not meet basic nutritional needs and should not be considered a healthy reset.

Claimed Water Fasting Benefits - What Does the Evidence Say?

Water fasting is often associated with claims such as improved hydration, appetite control, clearer skin, and toxin removal. However, these effects are either temporary, misunderstood, or unrelated to fasting itself.

Weight loss is largely water loss, and is commonly regained once normal eating resumes
Reduced appetite is often short-lived and may rebound strongly
Skin improvements are more closely linked to hydration, sleep, and overall nutrition
Detoxification is already handled by the body without fasting

In contrast, prolonged calorie restriction can slow metabolism, disrupt hormones, and negatively impact your relationship with food.

The Risks of Water Fasting

Water fasting carries several well-documented risks, particularly when undertaken without medical supervision. While it is often framed as a “natural” or “cleansing” practice, removing food entirely disrupts multiple physiological systems that rely on a steady intake of energy and nutrients. These risks tend to increase the longer fasting continues and are often understated in popular online advice.

Electrolyte and Mineral Imbalance

When food intake stops, the body loses a key source of electrolytes such as sodium, potassium, and magnesium. These minerals are essential for nerve signalling, muscle contraction, fluid balance, and heart rhythm. During water fasting, levels can drop rapidly, particularly if large volumes of water are consumed.

This imbalance can lead to symptoms such as headaches, dizziness, weakness, palpitations, and difficulty concentrating. In more severe cases, electrolyte disturbances may cause fainting or cardiac complications. These effects are not signs of “detox” but rather indicators that the body is struggling to maintain normal function in the absence of adequate nutrition.

Nutrient Deficiency

Even short periods of water fasting eliminate the intake of essential nutrients, including protein, essential fatty acids, vitamins, and trace minerals. Protein is particularly important for preserving muscle mass, supporting immune function, and maintaining metabolic rate. Without it, the body begins breaking down lean tissue to meet basic needs.

Micronutrients such as B vitamins, iron, zinc, and calcium are also required daily for energy production, oxygen transport, bone health, and immune defence. Repeated or prolonged fasting increases the risk of deficiencies, which can contribute to fatigue, low mood, impaired immunity, and reduced physical performance.

Poor Sustainability and Rebound Effects

Water fasting is not a sustainable approach to eating or weight management. While short-term weight loss may occur, it is largely due to water loss and depleted carbohydrate stores rather than meaningful fat loss. Once normal eating resumes, weight is commonly regained.

More importantly, extreme restriction often triggers cycles of deprivation followed by rebound eating. This pattern can disrupt hunger and fullness cues, increase preoccupation with food, and make long-term consistency more difficult. Over time, repeated fasting may undermine metabolic health rather than support it.

Increased Risk for Vulnerable Groups

Water fasting poses heightened risks for certain populations and should be avoided entirely. Individuals with diabetes, gout, or other metabolic conditions rely on regular nutrient intake to manage blood sugar and uric acid levels. Fasting can destabilise these conditions and increase the risk of complications.

Those with a history of eating disorders may find that fasting reinforces restrictive behaviours and unhealthy thought patterns. Pregnant or breastfeeding women, adolescents, and older adults have higher nutrient requirements and are particularly vulnerable to deficiencies. For these groups, water fasting is not only inappropriate but potentially harmful.

**So, How Long Should You Do Water Fasting?**

There is no recommended or necessary duration for water fasting from an evidence-based nutrition perspective. Even short periods offer no unique health benefits compared to safer alternatives - and carry avoidable risks.

If your goal is:

Better digestion
Improved energy
Weight management
A “reset” after overindulgence

You do not need to stop eating to achieve it.

What to Do Instead: Safer, Effective Alternatives

Rather than fasting, evidence supports approaches that nourish the body while reducing excess intake, such as:

Eating regular, balanced meals
Increasing vegetables, fibre, and protein
Staying well-hydrated
Reducing ultra-processed foods temporarily
Prioritising sleep and gentle movement

These strategies support metabolic health without triggering nutrient deficiencies or stress responses.

Healthy Meal Delivery UK

If you’re looking for a healthier reset without extreme restriction, Calo’s offers balanced, portion-controlled meals designed to support energy, digestion, and long-term wellbeing.

Rather than removing food entirely, Calo helps you eat consistently, nutritiously, and sustainably - all year round.

Download the Calo app to get started

FAQ

Is water fasting safe for weight loss?

No. Any weight lost is largely water weight and is typically regained. Water fasting also increases the risk of nutrient deficiencies and metabolic disruption. Aim for a lifestyle change that you’ll be able to commit to on an indefinite basis.

Does water fasting detox the body?

No, the body detoxifies itself through the liver and kidneys. Fasting does not enhance this process.

Can drinking water help control appetite?

Staying hydrated can support appetite regulation, but water alone cannot replace balanced meals or essential nutrients. It’s void of all three macronutrients and many micronutrients, too.

Despite its popularity online, water fasting is not a safe or effective approach to health or weight management. It offers no proven detox benefits and carries real risks - especially when compared to evidence-based, nourishing alternatives.

If you’re interested in sustainable approaches to nutrition, explore:

How to Stay Energised with Healthy Snacks

Should You Consume Smoothies for Gut Health

Visit the Calo Blog for expert-led, evidence-based guidance on nutrition, wellness, and long-term health.