Will Eating Fruit Stop My Low-Carb Ketosis?

by Anthony Marrone

About Anthony Marrone

Anthony Marrone holds a Ph.D. in kinesiology from the University of Michigan where he worked in both the athletic and nutrition departments. He began writing in 1985 and his writing has appeared in the "Journal of Strength and Conditioning Research" and the "American Journal of Clinical Nutrition."


Many diets help you lose body fat. For example, a ketogenic -- or low-carbohydrate -- diet is an effective method. You must restrict your total carbohydrate intake and specifically avoid certain types of carbohydrates to remain in ketosis. Consult a health care professional before beginning any dietary program.


Ketogenesis is the state where you are primarily burning free fatty acids, or ketones, for fuel. While your body will always burn sugar and amino acids to a degree, when your freely available sugar is depleted, your body may turn to ketones as its primary fuel. To achieve a ketogenic state, you must avoid all non-fibrous carbohydrates to deplete your glycogen, or sugar levels. This is accomplished more quickly with regular, intense exercise. Exercise depletes the glycogen in your muscles, and the more you deplete, the faster you achieve ketosis.

Glycemic Index

All non-fibrous carbohydrates have an effect on your blood sugar levels. Whether your source is fruit, grains or soda, all carbohydrates raise your blood sugar a hour or two after consumption. The degree to which your blood sugar is raised depends on both the quantity of carbohydrates you consume and the type. This is called the glycemic index, which is a rating scale from 1 to 100. The higher the number, the greater the spike in blood sugar levels. Fructose has a low glycemic index, generally around 20. This means fructose does not generate a large spike in your blood sugar levels, but will instead have a slower, more modest release of energy, according to a study published in the July 2002 American Journal of Clinical Nutrition.


While on the surface it may seem like fructose is the ideal choice due to its limited effect on your blood sugar and insulin levels, it is more complicated than that. One critical aspect of maintaining ketosis is the metabolic state of your liver. The more sugar your liver is processing, the harder it is for you to achieve and maintain a ketogenic state. Unfortunately, fructose is primarily metabolized in the liver by a specific enzyme. So while fructose does not have a great effect on your blood sugar levels, it will quickly shunt you out of ketosis. And depleting your liver will take some time again. So on a ketogenic diet it is best to avoid fructose.

Fruit Alternatives

If you are hungry for fruit, a good working knowledge of which fruits are high in fructose and which are high in other sugars can help satisfy cravings. Strawberries and blueberries, while healthy, contain fructose in one of its highest naturally occurring sources, and you should avoid them on a ketogenic diet. Fruits like watermelon are much lower in fructose although high in sugar. The only time you can consume a food like this is immediately after a workout. Assuming you have worked hard enough to deplete muscle glycogen, consuming simple sugars like those found in watermelon will be used to primarily refill your depleted muscle glycogen stores; do this sparingly.

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This article reflects the views of the writer and does not necessarily reflect the views of Jillian Michaels or JillianMichaels.com.