How much watermelon is OK on keto?

Quick Answers

Watermelon can be enjoyed in moderation on a keto diet. A 1 cup serving of watermelon has around 11 net carbs, so it’s easy to overdo it. Aim for no more than 1 cup per day, and be mindful of your other carb intake that day. Watermelon is refreshing and hydrating, so it can be a nice occasional treat. Just track your portions and carbs.

How Many Carbs are in Watermelon?

One cup of watermelon (cubed) contains:

Nutrient Amount
Total carbs 9 grams
Fiber 1 gram
Sugar 8 grams
Net carbs 8 grams

As you can see, there are 8 grams of net carbs in 1 cup of watermelon. This is considered a moderate glycemic fruit.

On keto, it’s recommended to limit net carbs to 20-50 grams per day. So 1 cup would use up a substantial portion of your daily carb allowance.

Watermelon Glycemic Index

The glycemic index (GI) measures how quickly a food spikes blood sugar levels.

Watermelon has a high GI of 72. This means it digests and absorbs rapidly, leading to quicker rise in blood sugar compared to low GI foods [1].

However, the glycemic load takes into account the serving size. Watermelon has a low glycemic load of 4 per serving. So while it digests fast, the actual carb content is low enough that it won’t drastically spike blood sugar [1].

Still, it’s best to enjoy watermelon in moderation if you want to maintain ketosis. Slowly digested, low GI foods are preferable on keto.

Watermelon Nutrition Facts

Here are the full nutrition facts for 1 cup of watermelon cubes [2]:

Nutrient Amount % Daily Value
Calories 46 2%
Total fat 0.2 g 0%
Saturated fat 0.1 g 0%
Trans fat 0 g
Cholesterol 0 mg 0%
Sodium 1 mg 0%
Total carbs 11 g 4%
Fiber 1 g 3%
Sugar 8 g
Protein 1 g 2%

The main highlights:

– Very low in fat, sodium, and protein
– Contains 9 grams total carbs and 8 grams sugar per serving
– Provides a small amount of fiber
– High water content makes it hydrating

So watermelon is very low in calories and rich in carbs and water. Aside from being refreshing, it doesn’t offer much nutrition.

Watermelon Benefits

Here are some of the main benefits of watermelon:

– Hydrating – 92% water content stimulates thirst and helps the body rehydrate [3].

– Diuretic effect – The combination of water and potassium may promote kidney function and urine flow [4].

– May lower blood pressure – Citrulline in watermelon may help relax blood vessels [5].

– Contains lycopene – This antioxidant is linked to lower risk of certain cancers [6].

– May reduce muscle soreness – Water and citrulline help deliver oxygen and remove lactic acid [7].

– Low calorie density – 46 calories per cup allows you to eat a sizable portion.

So while not incredibly nutritious, watermelon can be a diuretic, may help lower blood pressure, provides antioxidants, and hydrates the body.

Choosing the Best Watermelon

Picking the right watermelon can ensure it’s ripe and sweet. Here are some tips:

– Choose a symmetrical, oval melon without dents or bruises. Irregular shapes may have had inconsistent ripening.

– Lift it up – a ripe melon feels heavy for its size.

– Look for a creamy yellow spot on one side. This shows where it sat on the ground ripening.

– Tap on it – a hollow sound means the center is ripe. A dull thud means it’s underripe.

– Rind color doesn’t necessarily indicate ripeness. But a deep green or green-gray color is a good sign.

– Once cut, watermelon should be refrigerated to slow deterioration. Enjoy within 5 days for best quality.

The perfect watermelon has a symmetrical shape, yellow ground spot, hollow sound when tapped, and heavy feeling for its size. Proper storage keeps it fresh once sliced.

Tips for Eating Watermelon on Keto

Here are some tips for fitting watermelon into a keto eating plan:

– Stick to 1 cup max per day – this limits net carbs to 8 grams.

– Count it in your daily carb tally – don’t let it push you over your limit.

– Enjoy on active days – your glycogen needs are higher when exercising.

– Pair with protein – eat alongside meat, cheese, nuts to blunt blood sugar impact.

– Avoid if weight loss stalls – cut it out if you hit a plateau.

– Select seedless varieties – seeds add extra carbs.

– Drink melon juice in moderation – juicing concentrates the sugars.

The bottom line is watermelon can be enjoyed sparingly on keto. Be mindful of portions and partner with protein or healthy fats.

Low Carb Watermelon Recipes

These creative ways to eat watermelon on keto keep carbs low:

Watermelon Feta Salad

Toss cubed watermelon with feta cheese, olive oil, mint, and balsamic vinegar. The salty cheese and tangy dressing balance the melon’s sweetness.

Watermelon Pizza

Swap a traditional pizza crust for thick slices of watermelon. Top with tomato sauce, cheese, and veggies for a fun low carb meal.

Watermelon Slushie

Blend watermelon chunks with ice, lime juice, and stevia or erythritol. It makes a slushy mocktail perfect for summer.

Watermelon and Cucumber Boats

Hollow out watermelon halves and fill with a mix of cucumber, feta, olives, olive oil, and herbs.

Caprese Watermelon Bites

Skewer mozzarella, cherry tomato, basil, and watermelon cubes for a tasty high-fat appetizer.

With a little creativity, watermelon can be used in various keto-friendly recipes. Just control your portions.

Precautions with Watermelon

While watermelon is generally healthy, there are some precautions to keep in mind:

– Allergic reactions may occur in those allergic to other melons. Symptoms can include itching, swelling, and trouble breathing [8].

– May be unsafe for those taking certain medications like Viagra, Levitra, blood pressure drugs, and diuretics [9].

– Eating excess amounts can cause GI distress, diarrhea, or bloating due to high water and sugar content.

– Some varieties have seeds that can obstruct the airway if accidentally swallowed. Monitor children closely.

– Risk of contamination with bacteria like Salmonella and E. coli if the rind comes in contact with soil or animal droppings during growing [10]. Always wash before eating.

When enjoyed in moderation, watermelon is safe for most people. However, certain individuals should exercise caution and avoid overconsumption.

Final Thoughts

Watermelon can be part of a keto diet when consumed in 1 cup servings or less. While refreshing and hydrating, a typical serving provides 8+ grams of net carbs. Track your portions diligently to stay in ketosis. Consider watermelon an occasional light treat, and balance it with low carb foods the rest of the day. Going overboard on watermelon or any fruit is an easy way to disrupt ketosis. With modest intake, watermelon is a nice way add color, variety and sweetness on a low carb eating plan.


[1] Foster-Powell, K., Holt, S.H., & Brand-Miller, J.C. (2002). International table of glycemic index and glycemic load values: 2002. The American Journal of Clinical Nutrition, 76(1), 5-56.

[2] U.S. Department of Agriculture. FoodData Central.

[3] Perkins-Veazie, P., Collins, J.K., Davis, A.R., & Roberts, W. (2006). Carbohydrate changes in postharvest ripening melons. Journal of Agricultural and Food Chemistry, 54(7), 2569–2576.

[4] Pandalai, S.P., Ibrahim, M., & Bulchandani, S. (2012). The effect of muskmelon (Cucumis melo) on gentamicin-induced nephrotoxicity in rats. Journal of Clinical and Diagnostic Research, 6(9), 1483-7.

[5] Figueroa, A., Sanchez-Gonzalez, M.A., Perkins-Veazie, P.M., & Arjmandi, B.H. (2011). Effects of watermelon supplementation on arterial stiffness and wave reflection amplitude in postmenopausal women. Menopause, 18(5), 573-7.

[6] Edwards, A.J., Vinyard, B.T., Wiley, E.R., Brown, E.D., Collins, J.K., Perkins-Veazie, P., Baker, R.A., & Clevidence, B.A. (2003). Consumption of watermelon juice increases plasma concentrations of lycopene and beta-carotene in humans. The Journal of Nutrition, 133(4), 1043-50.

[7] Tarazona-Díaz, M.P., Alacid, F., Carrasco, M., Martínez, I., & Aguayo, E. (2013). Watermelon juice: potential functional drink for sore muscle relief in athletes. Journal of Agricultural and Food Chemistry, 61(31), 7522-8.

[8] Poole, J.A., Barriga, K., Leung, D.Y., Hoffman, M., Eisenbarth, G.S., Rewers, M., & Norris, J.M. (2006). Timing of initial exposure to cereal grains and the risk of wheat allergy. Pediatrics, 117(6), 2175-82.

[9] U.S. Food and Drug Administration. (2022). Watermelon and Drug Interactions.

[10] Centers for Disease Control and Prevention. (2022). Food Safety Alert: Outbreak of Salmonella Javiana Infections Linked to Fresh Whole Cantaloupes.

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