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What happens to your body when you start a juice cleanse?


A juice cleanse is a type of diet that involves consuming only fresh fruit and vegetable juices for a set period of time, typically ranging from 3 to 7 days. The goal of a juice cleanse is to “detox” or “cleanse” the body by flooding it with vitamins, minerals and phytonutrients while eliminating processed foods, dairy, gluten, meat, and other potential allergens or inflammatory foods.

Proponents of juice cleanses claim that going on a juice fast can improve energy levels, reduce bloating and inflammation, promote weight loss, remove toxins, and “reset” your metabolism or taste buds. However, many health professionals argue there is little scientific evidence to support these claims.

So what really happens, both good and bad, when you embark on a juice cleanse? Here is an overview of the potential effects, with subheadings on different bodily systems and functions.

Digestive System

Lack of fiber can cause issues: One potential downside of juice cleanses is that they contain very little fiber since the pulp is removed from fruits and vegetables during the juicing process. Fiber is important for healthy digestion and elimination. Without adequate fiber, you may experience constipation, bloating, and discomfort.

Nutrient absorption may be impacted: Some nutrition experts believe that removing the pulp from produce can impact how your body absorbs and utilizes certain nutrients. For example, fat-soluble vitamins A, D, E and K may not be absorbed as well without the fat and fiber from whole fruits and vegetables.

Detox claims are questionable: Many cleanses claim to “detoxify” your digestive system, but there is limited scientific evidence that juice cleanses can remove toxins. Your liver and kidneys naturally filter out toxins without the need for dramatic cleanses.

May impact gut bacteria: Consuming a limited diet for several days can alter the diversity of microbes in your gastrointestinal tract. It’s unclear if this is beneficial or could disrupt your gut health over the long term. More research is needed.

Weight Loss

You’ll likely lose weight temporarily: One of the biggest appeals of a juice cleanse is rapid weight loss, often between 2-7 pounds over a week. However, most of this initial weight loss is water weight or loss of muscle mass, not fat.

Muscle loss is a risk: Juice cleanses typically provide inadequate calories and protein. Without proper protein intake, your body may start breaking down lean muscle mass for energy, which can slow your metabolism.

Weight rebound is common: The low number of calories on a juice cleanse nearly always causes rebound weight gain after you finish. This yo-yo effect can be frustrating and unhealthy. For lasting weight loss, better to make sustainable diet changes.

Not a long-term solution: While juice cleanses may produce quick weight loss, they are extremely restrictive and difficult to maintain. They encourage deprivation rather than moderation. For long-term health, it’s better to develop balanced eating habits.

Energy Levels

Initial surge from nutrients: All the nutrients flooding your system during a juice cleanse may provide an initial boost of energy. However, this surge is often followed by decreased energy.

Calorie deficit can reduce energy: Your body relies on adequate calories and carbohydrates for energy. The very low calorie intake during juice cleanses can leave you feeling tired, dizzy and lethargic.

Blood sugar crashes: The high glycemic index of most fruit and veggie juices causes blood sugar spikes and crashes, which can drain your energy and mood. It’s better to eat whole produce which has fiber to slow sugar absorption.

Caffeine withdrawal may occur: Avoiding coffee while juice cleansing can lead to caffeine withdrawal headaches, fatigue, and brain fog. Caffeine has energizing effects for most people.

Lack of calories is unsustainable: While a short juice cleanse may provide an initial energy boost, continuing to deprive your body of adequate calories, protein, fat, and carbohydrates is unhealthy and unsustainable.

Immune System

May help if you cut inflammatory foods: Some nutritionists believe that removing inflammatory foods like dairy, gluten, meat, and processed foods may temporarily reduce inflammation and improve immune function. However, more research is needed.

Not proven to “boost” immunity: There is limited evidence that juice cleanses directly “boost” your immune system or help fight off illnesses. Your body’s immune response depends on adequate calories, protein, and nutrients, which cleanses lack.

Could have negative immune effects: Restricting calories and nutrients for multiple days may actually weaken immunity by depleting protein stores needed for immune cells. Micronutrient deficiencies are also possible.

Extreme diets add stress: The hunger, low energy, headaches, and other physical stress during a juice cleanse places additional strain on your body. This stress inhibits your body’s ability to fight viruses and other immune threats.

Can reduce gut bacteria diversity: Some research indicates juice cleanses can decrease the natural gut microbe diversity needed for a healthy gastrointestinal immune response.


“Resetting” metabolism is a myth: Claims that juice cleanses can “reset” or “rev up” your metabolism are not scientifically proven. Your metabolism is a complex system that adjusts based on age, muscle mass, genetics and calorie intake.

Calorie deficit can slow metabolism: Consuming too few calories during a juice cleanse can potentially slow your basal metabolic rate (BMR). When you reduce calories, your body tries to compensate by burning fewer overall calories.

Loss of lean mass slows metabolism: Juice cleanses provide inadequate protein, which may lead to loss of lean muscle mass. Having more muscle boosts your BMR, so losing muscle can slow your metabolism.

Temporary increase after cleanse: Your BMR may temporarily increase right after a juice cleanse as your body craves more food to make up for the deficit. However, this increase is unlikely to persist.

No shortcuts to boost metabolism: There are no quick fixes or “resets” for your metabolism. Achieving long-term increases in metabolic rate requires regular exercise and building lean muscle over time.


High in vitamins and minerals: Fresh fruit and vegetable juices are packed with vitamins, minerals, and plant compounds like antioxidants. However, juice cleanses still lack many essential nutrients.

Risk of calorie and protein deficiency: Juice cleanses typically provide only around 1000 calories per day or less, as well as inadequate protein intake. Consuming enough calories and protein is vital.

Lack of fat causes issues: Fat promotes the absorption of fat-soluble vitamins and provides fatty acids essential for your hormones and cell membranes. Juice cleanses contain almost zero fat.

Fiber intake is very low: Juices have minimal fiber since it is removed when the produce is juiced. Fiber is important for digestion, cholesterol levels, heart health, and feeling full after eating.

Nutrient absorption may decrease: Some studies find that nutrient uptake can be compromised without the fat and fiber of whole fruits and vegetables to help shuttle vitamins through your digestive tract.

Potential Side Effects

Here are some possible side effects that may occur during and after a juice cleanse:

– Headaches, dizziness, fatigue from low calorie intake
– Nausea, stomach pain from rapid change in diet
– Constipation, diarrhea from lack of fiber
– Hunger pangs, food cravings, mood swings
– Dehydration if not consuming enough water
– Irregular heartbeat from electrolyte imbalance
– Nutrient deficiencies long term if cleanses are repeated
– Weight gain after cleanse ends as body retains calories

These negative effects reinforce why health professionals advise against long or frequent juice cleanses. Moderation and a balanced diet is best.


While juice cleanses may seem like an appealing quick fix, they can often do more harm than good when it comes to your digestive health, energy levels, weight, immunity and nutrition. The extreme calorie and nutrient restriction can cause short term problems, as well as lasting complications if cleanses become a regular habit.

Instead of a juice detox, focus on getting your daily recommended fruit and vegetable intake from whole produce, not juices. Aim for balance, moderation and variety from all food groups. Be skeptical of any diet promising a “cleanse”, “reset” or “detox”. Your body already has its own built-in detoxification systems. The best way to support them is through adequate nutrient intake, not deprivation.

Pros Cons
  • Floods body with vitamins and minerals
  • Promotes initial feeling of energy and lightness
  • May support short term weight loss
  • Eliminates inflammatory or allergenic foods
  • Extreme calorie and nutrient restriction
  • Loss of lean muscle mass and slowed metabolism
  • Lack of protein, fat, and fiber
  • Blood sugar crashes and energy depletion
  • Weight rebound after cleanse ends
  • Starvation mode

In summary, while juice cleanses may seem tempting, their benefits are limited and temporary. You can get antioxidants, phytonutrients, vitamins, and minerals from whole fruits and veggies without the risks of calorie/nutrient deprivation. Focus on creating sustainable, healthy eating habits for the long-term rather than quick fixes and cleanses.