What will happen if I only eat fruits and vegetables for 3 days?

December 5, 2025 •

4 min read

According to a Northwestern University study, a vegetable and fruit juice-only diet for just three days can trigger shifts in gut bacteria linked to inflammation and cognitive decline. While often marketed as a 'cleanse' or 'detox,' restricting your diet to only produce for 72 hours can have a surprising array of effects on your body, both positive and negative.

Quick Summary

A 3-day diet of only fruits and vegetables is extremely restrictive, leading to an initial energy boost and potential water weight loss. It can also cause digestive discomfort, such as gas and bloating, and lacks essential nutrients like protein, healthy fats, iron, and B12. Sustainable, balanced eating is recommended for long-term health.

Key Points

Digestive Discomfort: A sudden spike in fiber from an all-produce diet can lead to gas, bloating, and cramps in the first 24-48 hours.
Initial Energy Boost, Followed by Fatigue: You may feel an initial lift from cutting out processed foods, but this is often followed by fatigue due to a severe caloric deficit and lack of protein.
Temporary Water Weight Loss: Any quick weight loss is likely from shedding water weight, not fat, and will return once you resume normal eating.
Nutrient Deficiencies: The diet severely lacks essential macronutrients like protein and healthy fats, as well as crucial vitamins like B12 and minerals like iron.
Mental and Emotional Toll: Restrictive eating can cause mental fogginess, intense cravings, and potentially lead to an unhealthy relationship with food.
Natural Detoxification is Key: Your body naturally detoxifies itself through organs like the liver and kidneys, and a restrictive diet is not necessary for this process.
Gradual Reintroduction of Foods: Coming off a restrictive diet requires care; reintroducing foods slowly is necessary to avoid digestive issues.

Day 1: The Initial Rush and Digestive Changes

On the first day of an all-fruit and vegetable diet, your body will likely experience some rapid changes. You are flooding your system with vitamins, minerals, and antioxidants, potentially leading to a temporary energy boost. The high water content in produce also promotes hydration. However, for many people, the most noticeable effect is digestive upset. The sudden, significant increase in fiber can overwhelm your system, potentially leading to gas, bloating, and abdominal cramps.

Morning: You might wake up feeling surprisingly energized, a result of removing processed, high-sugar foods from your diet. The high water content from fruits like melon or berries can leave you feeling refreshed.
Afternoon: You might feel full due to the high volume of fiber and water in your meals, but also still feel hungry because of the low-calorie density. Cravings for more calorie-dense foods, like fats and proteins, might start to creep in.
Evening: As your digestive system continues to process the high fiber intake, you may notice increased gas and bloating. Dinner could consist of a large salad, which adds more bulk and roughage to your system.

Day 2: Fatigue and Nutrient Deficiencies Appear

By the second day, the initial energy spike might give way to fatigue. This is because your body is operating on a significant calorie deficit, and without sufficient protein, it can't properly repair and build muscle. Fruits and vegetables, while packed with micronutrients, do not provide the complete nutritional profile your body needs for sustained energy. Crucial macronutrients like protein and healthy fats are severely lacking.

Lack of protein: Without protein, your body can begin to break down muscle tissue to supply essential amino acids. This can cause weakness and contribute to the fatigue you feel.
No healthy fats: Essential fatty acids, particularly Omega-3s, are not present in fruits and vegetables. These are critical for brain function and reducing inflammation. A lack of these fats over even a short period can start to impact your mood and focus.
Possible blood sugar fluctuations: Eating a large amount of fruit can cause natural sugar spikes, especially for individuals with blood sugar sensitivities, though the fiber helps to mitigate this. This can cause energy levels to yo-yo throughout the day.

Day 3: Continuing Side Effects and What's Next

The final day often brings the cumulative effects of the previous 48 hours. The digestive issues may persist as your gut microbiome adjusts to the new, high-fiber intake. Fatigue and mental fogginess are likely to be more pronounced as your body continues to conserve energy due to the low caloric intake. While some people experience temporary water weight loss, this is not true fat loss and will likely be regained once a normal diet is resumed. The restrictive nature of the diet can also lead to intense cravings and a potential for binging afterward, which can be detrimental to healthy eating habits.

Comparison of a 3-Day All-Produce Diet vs. a Balanced Diet


Feature	3-Day All-Produce Diet	Healthy, Balanced Diet
Calorie Intake	Significantly low, often leading to a large deficit.	Varied, to meet daily energy needs for optimal function.
Macronutrients	Deficient in protein and healthy fats.	Includes adequate protein, fats, and carbohydrates from diverse sources.
Micronutrients	High in some vitamins and minerals, but deficient in others like B12 and iron.	Balanced and comprehensive intake from a wide variety of foods.
Energy Levels	Initial spike followed by significant fatigue and potential sluggishness.	Stable and sustained energy throughout the day.
Weight Loss	Primarily temporary water weight loss.	Gradual and sustainable fat loss, when combined with exercise.
Gut Health	Risk of digestive upset, gas, bloating, and potential microbiome disruption.	Fiber promotes healthy digestion and a balanced gut microbiome.
Sustainability	Not sustainable and can lead to unhealthy eating cycles.	A sustainable lifestyle approach to long-term health.

Conclusion

While a 3-day all-fruit and vegetable diet can be a refreshing and vitamin-rich reset for some healthy individuals, it is not a sustainable or nutritionally complete long-term solution. For a short period, it might result in temporary water weight loss and an initial boost of energy from cutting out processed foods. However, the associated risks, including digestive issues, significant calorie deficits, and deficiencies in essential macronutrients like protein and healthy fats, outweigh the purported 'detox' benefits. Your body has natural detoxification systems, and a balanced diet with a variety of food groups is the most effective and safest approach for sustained well-being. Anyone considering a restrictive diet should consult a healthcare professional first.

Transitioning Off the Diet Safely

If you have completed a short-term cleanse, the reintroduction of solid foods must be done carefully to avoid further digestive upset. Start with small portions of easily digestible foods like cooked vegetables, plain yogurt, and broth before moving on to grains, beans, and lean proteins. A gentle transition can help your system readjust and prevent bloating or discomfort.

For more information on transitioning back to a balanced diet, reputable sources like WebMD offer guidance on easing back into regular eating patterns. A mindful and gradual approach is key to maintaining any positive effects and avoiding a post-cleanse crash.

This article is for informational purposes only and is not medical advice.

Frequently Asked Questions

You may experience a temporary loss of water weight, but not significant or sustainable fat loss. Any lost weight will likely return once you resume your regular diet.

No, a diet of only fruits and vegetables is nutritionally incomplete. It lacks essential nutrients like protein, healthy fats (Omega-3s), Vitamin B12, and iron, which are vital for proper body function.

For most healthy individuals, a short-term cleanse is unlikely to cause serious harm, but it is extremely restrictive and unbalanced. It's not recommended for those with pre-existing health conditions, and you should always consult a doctor before starting.

Common side effects include digestive issues like gas, bloating, and cramps due to the high fiber intake. You may also experience fatigue, weakness, and mood fluctuations.

You might feel an initial burst of energy from cutting out processed foods, but this is often short-lived. A low-calorie and protein-deficient diet will likely lead to low energy and increased fatigue.

Reintroduce solid foods slowly, starting with small portions of easily digestible foods like cooked vegetables, broth, and plain yogurt. Gradually add grains, beans, and lean protein back into your meals.

It is generally better to eat whole fruits and vegetables to retain the fiber. Juicing removes much of the beneficial fiber, which can lead to blood sugar spikes and potentially disrupt your gut microbiome.