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Why Do I Feel Sick after Eating Fruit?

author avatar Dr. Eric Berg 08/31/2023

Most people believe that fruits are nutritious and part of a healthy diet, but is this really the case? The answer is no—most fruits aren’t a healthy addition to your diet. 

Fruits can contain staggering amounts of sugar and can make you feel sick. Let's look into why fruits are the wrong choice for your health and not a keto-friendly food.  

Fruit high in fructose

Is fruit healthy?

The majority of calories in fruit come from fructose, a type of sugar found only in fruit.

 

Most fruits offered in supermarkets today are selectively grown for their sweetness, catering to the ever-increasing sweet tooth of the consumer. Depending on the variety, some fruit can contain as much as 90 grams of fructose. 

Too much sugar can cause obesity, diabetes, and many other health conditions—so classifying fruit as healthy food is inaccurate.

Fructose is sweet, but it’s not the same as table sugar or refined carbs. Fructose isn’t converted to blood sugar and has to be metabolized by your liver. While your liver can process some fructose, large amounts can quickly overwhelm your liver’s capacity, resulting in metabolic and hormonal imbalances. 

Research confirms that consuming fructose contributes to insulin resistance, elevated cholesterol, and imbalanced blood lipids and is linked to the development of diabetes. 

Because fructose intake has metabolic consequences, eating fruit prevents weight loss, pushes you out of ketosis, and overburdens your liver. Watch the below video to learn more about why eating fruit isn’t the best way to support a healthy body.

Reasons you don’t feel well after eating fruit

There are several reasons why you may feel sick after eating fruit. 

Eating fruit on an empty stomach can lead to nausea. Fructose draws water into your stomach resulting in bloating, digestive issues, and feeling sick.

Fructose feeds harmful bacteria in your gut, and eating fruit can cause small intestinal bacterial overgrowth, also called SIBO. As fructose gets fermented by bacteria, you can feel nauseous and experience abdominal pain and diarrhea.

You may also feel sick after eating fruit if you have a food intolerance, causing nausea, diarrhea, and other digestive system issues.

Insulin resistance explained

Insulin is a pancreatic hormone that regulates blood sugar levels and energy metabolism. It's mainly produced in response to carbs and sugars. However, protein and eating foods in general also cause insulin to rise.

Insulin opens your cells to either use blood sugar for energy production or to store unused sugars as fat. However, elevated insulin levels over long periods can cause your cells to become less responsive to insulin, leading to insulin resistance.

Insulin resistance causes disruptions in energy production and metabolic functioning, weight gain, especially belly fat, and increases your risk of diabetes and heart disease.   

Signs of insulin resistance:

  1. Need for frequent meals and snacks

  2. Inability to lose weight and belly fat

  3. High cholesterol

  4. High blood pressure

  5. Excessive urination at night

  6. Feeling tired and fatigued 

Sugary foods

Seven health consequences of sugar

Experts have long confirmed that sugar is addictive and linked to adverse health effects. Avoiding simple carbohydrates and sugary snacks supports healthy weight, helps maintain steady energy levels, and improves nutritional deficiencies.

Let's take a look at the health consequences of sugar intake.

1. Sugar causes weight gain 

Sugary foods cause high blood sugar levels and raise insulin. While sugar can be used as a fuel source, high blood glucose levels after eating sugar are likely to provide more energy than you will need. 

Insulin signals your body's cells to store excess sugar as fat, explaining why eating sugary snacks leads to weight gain.

2. Sugar drains energy and causes fatigue 

Sugar raises your blood glucose levels sharply, and your body releases more insulin than is needed to keep blood sugar levels balanced. This results in low blood sugar levels, also known as hypoglycemia, shortly after eating the sugary food. 

Hypoglycemia causes fatigue, brain fog, and headaches. More importantly, low blood sugar triggers sugar cravings to quickly raise blood sugar levels back to normal. This sets you up for a blood sugar rollercoaster ride of cravings and low energy throughout your day.    

3. Sugar causes insulin resistance 

Insulin is released in response to eating carbs and sugars. Over time, your body's cells can become less reactive to insulin, resulting in insulin resistance. 

Insulin resistance is a serious metabolic imbalance linked to diabetes and heart disease. 

Obese man

4. Sugar increases risk of diabetes 

Elevated blood sugar has profound health consequences. Once your cells become insulin resistant, your body can no longer control blood sugar levels, resulting in diabetes. 

Uncontrolled blood sugar causes red blood cells to combine with sugar and become stiff and dysfunctional. These glycated blood cells are larger in size. They can block blood flow to nerve endings and tissues like the retina, causing nerve damage and vision loss, both side effects of diabetes.

5. Sugar worsens inflammation

Insulin doesn't just control blood sugar. It also is involved in inflammation. 

Your immune cells produce inflammatory compounds whenever insulin is elevated, explaining why sugar intake worsens inflammatory conditions like acne, eczema, or arthritis

6. Sugar depletes nutrients 

Eating sugar takes a toll on your nutrient stores. Carbohydrate metabolism requires vitamin B1, chromium, and magnesium. Frequent sugar intake can deplete your body of essential nutrients.  

Nutrient deficiencies slow energy metabolism, imbalance hormone production, and worsen insulin resistance.

7. Sugar impacts your mental well-being

Imbalanced blood sugars can negatively impact your mental health. Your brain relies on steady levels of fuel to function. 

Too much sugar in your bloodstream creates a stressful environment for your central nervous system, triggering anxiety attacks and worsening depression symptoms.

Woman holding sugar cubes

Key takeaways

Fruits are typically high in fructose, with some varieties containing as much sugar as candy. Large amounts of fructose can overwhelm your liver and negatively impact your metabolism, increasing your risk of weight gain, insulin resistance, and diabetes.

Fructose can trigger digestive issues and bloating and can explain your nausea and abdominal pain after eating fruits.   

Avoiding sugars will help keep your blood glucose levels healthy, balance insulin, and support weight loss. Read nutrition labels to spot added sugars to benefit from lower inflammation, increased energy, and improved mental well-being.

Take this body type quiz to help determine the best diet and nutrition for your body type.

FAQ

1. Why do I feel sick after having fruit?

Fruits are high in fructose, a simple sugar found in fruit. Fructose can draw fluids into your stomach, causing bloating, nausea, and sickness.

Fruits can also worsen small intestinal bacterial overgrowth or SIBO. Fructose feeds harmful bacteria in your small intestine resulting in digestive symptoms like diarrhea and nausea. 

2. Why do I feel sick after eating sugar?

If you are feeling sick after eating sugar, your body might not be very effective in controlling blood glucose. Sugar intolerance, insulin resistance, nutrient deficiencies, or eating too much sugar can make you feel sick.

Sugar can also cause elevated blood glucose levels, also known as hyperglycemia. Chronic hyperglycemia increases the risk of insulin resistance and diabetes.

Early warning signs of diabetes include increased need for urination, thirst, headache, and nausea. 

Low blood sugar, also known as hypoglycemia, may cause you to feel sick after eating sugar. Sugary foods raise blood glucose levels sharply and your body responds by releasing more insulin than is needed to keep blood sugar levels balanced. This results in low blood sugar levels shortly after you eat sugar. Nausea and feeling sick are common symptoms of low blood sugar.

3. Is nausea a symptom of diabetes?

Yes, nausea is a common symptom of diabetes. Diabetic ketoacidosis, diabetic gastroparesis, and some injectable medications used to treat diabetes increase the risk of nausea.

You may use sugar alternatives if you have diabetes. Some sugar alcohols and other artificial sweeteners can cause digestive issues and nausea.

4. What is insulin resistance?

Excessive amounts of carbohydrates and added sugar lead to chronically elevated insulin to keep blood sugar within a healthy range. Over time, your cells become less reactive to insulin,  leading to resistance. When left untreated, insulin resistance can contribute to serious health conditions like diabetes, high blood pressure, and heart disease.

5. How do I know if I have insulin resistance?

Early warning signs of insulin resistance are the inability to lose weight and belly fat, high blood pressure and cholesterol, need for frequent meals and snacks, excessive urination at night, and feeling tired.

If you experience any of these symptoms, consult your doctor to determine your blood sugar and insulin levels.

6. Can I eat fruit on keto?

While most fruits are high in carbs and not a keto-friendly option, berries are nutritious, rich in fiber, and small amounts won’t interfere with ketosis. Blackberries, black currants, blueberries, and raspberries are great additions to your Healthy Keto® diet.

7. Can I have fruit after I become keto-adapted?

Most fruits are high in simple sugars. It would be best if you avoided them to stay in ketosis and take advantage of keto’s many health benefits.

8. What kind of fruit can I have on keto?

Berries are rich in fiber and are excellent sources of nutrients. Small amounts of low-carb berries won’t push you out of ketosis and are okay to include as part of your Healthy Keto diet. 

Choose low-carb berries like raspberries, blueberries, strawberries, and blackberries. 

9. How much fruit can I have on keto?

You can enjoy around one cup of low-carb fruits like raspberries, blueberries, strawberries, and blackberries daily.

10. Are berries safe on keto?

Berries are low in net carbs, and adding around one cup per day is safe on keto.

11. Does sugar cause inflammation?

Yes, sugar worsens inflammation. Sugar leads to weight gain and visceral fat, the type of fat surrounding your organs. Visceral fat slows your metabolism, increases the risk of heart disease, and increases inflammation.

Your immune cells produce inflammatory compounds whenever insulin is high, explaining why eating sugar can make inflammatory conditions like acne, eczema, or arthritis worse. 

12. Is fruit juice keto-friendly?

No, fruit juice isn’t keto-friendly. The large fructose content of fruit juice can quickly overwhelm your liver's capacity to process fructose. Fruit juices are also heavily processed, resulting in the loss of fiber and most nutrients. 

13. How much sugar will kick me out of ketosis?

To maintain ketosis, consume no more than 20 to 50 grams of net carbs daily. Count all sugars, syrups, and honey towards your daily net carb count to stay within your daily carb limit.

Healthy Keto Guide for Beginner

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