What Happens If You Eat Sugar on Keto?

minute read | Last update: Nov 29th2022

This article is backed by studies and reviewed by a certified dietician.

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You’re only human, and that means getting cravings for foods you shouldn’t eat even when you’re dieting. You have a cheat day coming up and you’re dying for some sugar. Is it okay if you have just a little bit or is that sugar going to knock you out of ketosis?

Eating sugar can indeed stop your ketosis, which means you’re no longer burning fat. Further, your stomach could hurt, reentering ketosis a second time could be more difficult (keto flu, anyone?), and you could even incur blood vessel damage.

Whew! We know we just threw a lot at you all at once, but don’t worry. Ahead, we’ll explain the risks of ingesting sugar on the keto diet and talk about whether sugar has any spot in your cheat day meals. Make sure you keep reading!

What Happens If You Eat Sugar on the Keto Diet?

We’re sure you won’t be surprised to read that sugar isn’t good for your health. It tastes great, but it doesn’t benefit your waistline, muscle tone, or any of the health goals you’re trying to achieve.

Yet the real risk of eating sugar on the keto diet is that sugar is laden with carbohydrates.

One teaspoon of table sugar contains 4.2 grams of carbs. Now think of how many teaspoons of sugar you dump into your morning coffee or your favorite baked good recipe.

A teaspoon of packed brown sugar contains 4.5 grams of carbs, and a teaspoon of unsifted powdered sugar has eight grams.

Keeping all that in mind, here’s what can happen if you make sugar a part of your diet on keto.

Could Stop Ketosis

Ketosis is the ultimate goal for those on the keto diet.

After depriving your body of carbs for several days, your body will have burned through the last carbs you’ve eaten as well as any that may be in reserve.

Your body still needs energy to function, and this is where ketones come in.

Ketone bodies are produced in the liver. They can act as an alternate energy source when your body has no energy from carbs.

This is how you start burning fat, which is what makes the keto diet so worthwhile.

Once you enter ketosis, you’ll want to maintain it. The best way to do that is to continue to eat a low-carb diet that includes no more than 50 grams of carbs per day.

Knowing how carb-heavy sugar is, if you indulge in one sweet treat, you’re very likely to consume enough carbs to disrupt ketosis.

Your body will have carbs to use for energy and thus doesn’t need ketones anymore. Your liver may cease producing ketones until it has to again.

You’ve stopped burning fat, and while your keto diet may allow you to lose weight since cutting carbs usually means slashing calories too, burning fat and burning calories are two different things.

May Cause Indigestion

Now that you’ve been on the keto diet for a while, your body has gotten used to your lower-carb lifestyle.

It’s enough that your body might not immediately recall how to process large quantities of carbs like the ones you just ingested when you had that slice of cake or cinnamon roll.

The result? Your stomach is not going to feel well. You could experience an upset stomach, nausea, and diarrhea.

Makes Reentering Ketosis Difficult

Some keto dieters have even experienced a harder time getting back into ketosis after indulging in a sweet treat or several.

This is likely because you caused such a huge shift in your body by reintroducing carbs.

Think of your diet like a pendulum. For weeks or months, you’ve eaten low-carb, and so the pendulum has risen more and more in one direction.

After a cheat meal full of ice cream or cheesecake, the pendulum swings the other way. The aftereffects of that are hard to predict.

You might experience keto flu as you enter ketosis after a high-sugar, high-carb evening of eating.

For those who don’t remember because it’s been so long, keto flu can lead to side effects such as constipation, sleeping troubles, nausea, moodiness, fatigue, brain fog, and headache.

You’ll usually experience keto flu for two days to a week after you start the diet. The symptoms can persist for one to two weeks.

May Lead to Blood Vessel Damage

Now here is some food for thought.

In 2019, the journal Nutrients published a report that involved nine participants who first ate a diet that was similar to keto and then incorporated sugar into that diet. All the participants were men and were younger.

For a week, the men ate food that contained 20 percent protein, 10 percent carbs, and 70 percent fat. While not the ketogenic diet by name, the diet was awfully similar to keto.

Before they started eating low-carb, the participants drank a glucose beverage that was approximately 75 grams. The men repeated this after the seven days of their special diet.

According to the researchers, all the participants had poor-quality blood vessels after completing the study. The quality of each participant’s blood vessels was likened to “people with poor cardiovascular health.”

So what happened?

The researchers believe that as your blood sugar goes up after not having been elevated for a while, the body can undergo a metabolic response that could activate cellular blood vessel death.

Now, we must note that this study had an incredibly small sample size with only nine participants. They were also about the same age and the same gender.

Would these results recur if the study was done on younger women? What about older men or older women?

Until we can answer these questions definitively, we cannot say for sure that eating sugar on a low-carb diet will cause blood vessel damage. That said, the possibility is there.

Low-Carb Sugar Sources That Are More Keto-Friendly

Are you craving sugar and nothing else will do, but you don’t want to knock yourself out of ketosis?

You can have your cake and eat it too (well, so to speak, as you’re not actually eating cake).

While many fruits are too high in carbs to be viable on the keto diet, the following lower-carb fruits will help you stay in ketosis and stop your sugar cravings in one fell swoop.


A half-cup serving of honeydew contains eight grams of carbs, 31 calories, one gram of fiber, 7 grams of sugar, 15 milligrams of sodium, and zero milligrams of cholesterol.

Honeydew has a toothsome texture and is much sweeter than cantaloupe, a fruit the honeydew is often compared to. That sweetness ought to nullify your urge for sugar.


Although you can’t eat them canned and baked into a pie, raw peaches are still a tasty treat that makes for a great mid-afternoon pick-me-up.

A medium-sized, 147-gram peach contains 15 grams of carbs, 50 calories, one gram of protein, two grams of fiber, zero grams of sodium, zero grams of cholesterol, and 0.5 grams of fat.

You also get 15 percent of your daily serving of vitamin C and six percent of vitamin A!


How about some berries? Yummy and delicious, blackberries are low-calorie and don’t contain so many carbs that you’ll stress about your macros for the rest of the day.

A cup of raw blackberries has 14 grams of carbs, 62 calories, seven grams of sugar, eight grams of fiber, under one gram of fat, and two grams of protein.


The penultimate summer fruit, ruby red strawberries are a great way to deal with your urge to eat sugar. You can’t dip them in table sugar or chocolate, but after going low-carb for so long, a serving of strawberries will satisfy.

A 100-gram or 3.5-ounce serving of strawberries contains 7.7 grams of carbs, 32 calories, 0.3 grams of fat, two grams of fiber, 4.9 grams of sugar, and 0.7 grams of protein.


Handheld and bitable, raspberries are yet another berry that slots well into your keto diet when you need to eat something sweet.

Raspberries have 14.7 grams of carbs, 64 calories, 0.8 grams of fat, 1.5 grams of protein, and eight grams of fiber in a 123-gram serving.

Plus, you’re getting six percent of your recommended daily value of copper as well as potassium (five percent), phosphorus (four percent), magnesium (seven percent), iron (five percent), B vitamins (up to six percent), vitamin E (five percent), vitamin K (41 percent), manganese (41 percent), and vitamin C (54 percent of your recommended daily value!).


Watermelon might be mostly water, but it’s undeniably sweet as well.

A cup of diced watermelon that’s 152 grams contains 11 grams of carbs, 46 calories, 0.2 grams of total fat, two milligrams of sodium, nine grams of sugar, and 0.9 grams of protein.

Eating watermelon is a good source of vitamin C (20 percent of your recommended daily value), vitamin B6 (five percent), magnesium (three percent), and iron (two percent of your recommended daily value).


Eating sugar on keto can stop ketosis in its tracks and make reentering ketosis challenging since your body is wildly fluctuating between processing few carbs and then heavier amounts of carbs.

If you want to maximize your results on the keto diet, you should try to avoid carbs and sugar as often as you can, even on cheat days!

About the author

The Authentic Keto Team is here to bring you health tips that help you with losing weight fast. We focus on a clean keto diet for beginners because we believe that is the easiest and most simple way to healthy eating. Our keto weight loss tips will not only bring you into ketosis fast but will also help you to improve your mental health, sleep problems, and wellness.

- Our goal is to make keto success easy. -

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