Is Watermelon a Good Fruit for Weight Loss?

Watermelon is a hydrating summer staple, and it’s supposed to be healthy, right? Find out if this low-calorie seasonal fruit is actually helpful for weight loss and managing blood sugar.

slices of watermelon on a table outdoors

Why Is Watermelon So Popular? 

A little bit of background about the watermelon. The first variety of watermelon was grown in Africa. The large fruit demanded lots  of sun and space, and the hot climate of the region was a perfect environment for this mouthwatering melon. 

The original watermelons were much less sweet than the common varieties we recognize today, which were cultivated approximately 2000 years later in the Mediterranean.1

Ripe watermelon is sweet, easy to serve, and a crowd-pleaser. It is a healthy addition to your meals that can align with your weight loss goals, but remember: variety in your diet is key for good health! 

I've Heard Of The Watermelon Diet, What Is That? 

The watermelon diet more closely resembles a cleanse rather than an actual diet. The creators of the watermelon diet are unknown, and there are different variations of the diet circulating online. 

The general guidelines for the watermelon diet suggest eating nothing except watermelon for three days. Advocates say this will help you lose weight fast, and after three days you can return to your normal eating habits. 

It might sound appealing at first; who wouldn’t want to only eat fruit all day? In reality, only eating watermelon leaves a large gap in your nutritional needs. 

This pink and green fruit is rich in nutrients and essential vitamins, but it doesn’t offer protein and is considered low in fiber. 

Does the Watermelon Diet Work? 

The marketing around the watermelon diet promises rapid weight loss. But the science to back up these claims doesn’t exist, and any weight you do lose is likely just water weight, not true body mass. 

Prescriptive and rigid diets, like the watermelon diet, are packaged nicely and make weight loss look easy. Although the thought of following a simple diet for three days and getting amazing results is appealing, sustainable weight loss simply doesn’t work that way.

Long-lasting results require you to make a long-term commitment to your health and your goals. Keep educating yourself on the impact of proper nutrition and you will increase your chances of experiencing long-term results—you can do this! 

Watermelon Nutrients and Health Benefits

Many people do not know that all parts of the watermelon are edible. The pink interior is the easiest to eat, but you can also eat seeds and even the rind. 

The core nutrients in watermelon2 are:

  • Vitamin C 
  • Vitamin A 
  • Lycopene 
  • Water (of course!) 

Vitamin C is an antioxidant that supports your immune system3 and is a vital precursor to collagen synthesis, which helps you maintain healthy glowing skin.4

Vitamin A is a fat-soluble vitamin, meaning that it is the best absorbed when combined with a little bit of healthy fat. It helps maintain healthy vision, promotes healthy cell growth, and is also an active player in your immune system.5

Lycopene is another type of antioxidant that can help manage blood pressure, improve serum lipid levels, and decrease inflammation.6 Lycopene is also present in tomatoes, but researchers are still studying if the lycopene in watermelon can help support your health in these areas.7

How to Eat Watermelon Seeds

Save your watermelon seeds and roast them in the oven. They have a texture and flavor similar to sunflower seeds, but are less intense when eaten raw. Roasting them will bring out the natural flavors and increase their appeal. 

To increase the crunch, soak your watermelon seeds in salt water for up to an hour prior to baking. When you’re ready to roast, drain the water and pat the seeds dry with a paper towel. Place a parchment paper over a baking sheet and bake your seeds at 320°F for approximately twenty minutes. 

Watermelon seeds are small and should not take any longer than that. Allow them to cool before eating, and then sprinkle them into salads, granola, or yogurt. Watermelon seeds contain protein and iron, which are essential to a well-rounded diet.8 

woman sitting on the beach eating watermelon with seeds
Watermelon seeds have iron, zinc, potassium and other essential nutrients.

What Are Mini Watermelons? 

Mini watermelons are much smaller than regular-sized watermelons; they are usually the same size as a cantaloupe or honeydew melon. These smaller versions are called Sugar Baby watermelons, and they are a great option when you want to grow a watermelon but you have limited garden real estate available. 

Sugar Baby watermelons are slightly less flavorful than a full-sized melon, but the nutritional content is very close. You may choose to buy a mini watermelon if you have fewer mouths to feed because one large fruit can be too much for one person. You can prepare and eat a mini watermelon the same way you would eat a regular watermelon. 

How Eating Watermelon Can Support Healthy Weight Loss 

Watermelon can fit into your healthy weight loss journey, but it shouldn’t be the only thing you eat! 

From a caloric perspective, a slice (which is approximately 1/16th of a watermelon) is quite low, with only 86 calories.2

Watermelon has high water content and is hydrating. It is a great way to quench your thirst without relying on flavored or sweetened beverages. 

<p class="pro-tip"><strong>Learn about </strong><a href="/blog/water-lower-blood-sugar">hydration and blood sugar</a></p>

A Great Post-Workout Snack

All fruits, including watermelons, have simple sugars which are an essential source of energy for your muscles and your brain. 

The natural sugars will help you maintain consistent energy levels throughout the day, which will help you stay active and meet your exercise goals. 

Athletes love watermelon because it helps them cover their bases with only one food: simple sugars to replenish their glycogen stores, and fluid to avoid getting dehydrated. 

The Glycemic Index of Watermelon 

Previous to 2021, researchers clocked the glycemic index (GI) fruit of watermelon to be high (scoring above >70).9 Classically, a high GI food is expected to have a greater impact on your blood sugar—also called glycemic response

In 2021, the University of Sydney published a new GI score for watermelon of 50, bringing the final GI ranking into the low range.10 Other low GI fruits include apples, red grapefruits, and green bananas. 

The new GI was calculated by using an average score of four popular types of watermelon sold across the globe. In the US the GI of watermelon is ranked at 72. 

<p class="pro-tip"><strong>Learn about </strong><a href="/blog/how-glycemic-index-and-glycemic-load-impacts-glucose">the glycemic index & glycemic load</a></p>

In America and Australia, the guidelines surrounding watermelon are positive! Both countries suggest including watermelon in moderation and adding variety to your diet by including other fruits as well.  

two women sitting on a playground eating watermelon after working out
Eating watermelon after exercise can help replace fluids and electrolytes lost through sweating.

How to Include Watermelon in Your Diet to Support Weight Loss 

Watermelon is an ingredient you can have a lot of fun with. You can lean into the sweet flavor, or flip it around and pair it with savory components. Try sprinkling chili powder on your fresh watermelon slice to add some heat and smokiness to your snack! 

Include diced watermelon in salads or feature it as a star ingredient. Popular watermelon salad recipes also call for feta cheese, red onion, and fresh mint. Check out even more low-glycemic recipes that feature a lot of popular summer flavors and deliver on the foodie factor. 

If you love smoothies, you may try cutting up and freezing watermelon cubes to use in a blender. Try not to let any seeds sneak into your smoothie—depending on the quality of your blender, they may not get broken down.

Is There a Best Time of Day to Eat Watermelon? 

There is no best time to eat watermelon for weight loss. Any time of day is appropriate to eat watermelon. 

Watermelon is a carb-based food, and to stabilize your blood glucose response, it is wise to pair it with a healthy fat or high protein item to slow down digestion.

An example of this would be to make a snack plate that features fresh watermelon, slices of cheese, and a handful of nuts. This mimics a charcuterie board and is a perfect option when you feel like grazing. 

<p class="pro-tip"><strong>Learn about </strong><a href="/blog/achieve-stable-blood-sugar-levels-with-these-everyday-foods">7 everyday foods that stabilize blood sugar levels</a></p>

Can You Eat Too Much Watermelon?

Too much watermelon can leave you feeling bloated, uncomfortable, and potentially with diarrhea. People who are sensitive to fructose are even more prone to these side effects, and they should be mindful of their watermelon intake.11

Watermelon is high in potassium, which can raise serum potassium levels; this condition is called hyperkalemia. People suffering from kidney disease are at high risk for elevated potassium levels and need to be careful. 

High potassium in your blood can result in irregular heartbeats and, in certain circumstances, can be life-threatening.12 Your medical team will advise you if you need to monitor or reduce your potassium intake. 

The USDA food database recognizes one serving of watermelon to be approximately 280g (about 1/16th of a watermelon).2 A healthy adult can safely eat 1-2 servings of watermelon per day. 

How to Track Your Body's Response to Eating Watermelon Using a CGM

Everybody will metabolize food and drink differently. Although watermelon is generally accepted as a healthy part of a balanced diet, you won’t know how it directly impacts your blood glucose levels unless you use a continuous glucose monitoring (CGM) device. 

To directly observe how watermelon affects you, try to only eat the fruit by itself and then watch your data. Key points of interest will be how quickly your blood sugars rise and then fall. Ideally, this movement should be gradual, with little spiking and no sudden drop-offs. 

The next step is to pair watermelon with foods that delay blood glucose absorption: high fiber foods, protein-rich options, and healthy fats. You can combine your fruit with a slice of cheese as mentioned above, or in a fruit salad served alongside a hardboiled egg.

If you can, try and keep your portion sizes consistent. This will help ensure the data you collect in your CGM is consistent and will help give you greater insight into how watermelon and any food pairings are impacting your blood sugar. 

<p class="pro-tip"><strong>Learn about </strong><a href="/blog/cgm-data-weight-loss">using CGM data to crack the weight loss code</a></p>

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References

  1. Paris H. S. (2015). Origin and emergence of the sweet dessert watermelon, Citrullus lanatus. Annals of botany, 116(2), 133–148. https://doi.org/10.1093/aob/mcv077
  2. U.S. Department of Agriculture, Agricultural Research Service, FoodData Central (2019). Watermelon, Raw. Retrieved June 9, 2022, from: https://fdc.nal.usda.gov/fdc-app.html#/food-details/167765/nutrients
  3. Carr, A. C., & Maggini, S. (2017). Vitamin C and Immune Function. Nutrients, 9(11), 1211. https://doi.org/10.3390/nu9111211
  4. Sauberlich H. E. (1994). Pharmacology of vitamin C. Annual review of nutrition, 14, 371–391. https://doi.org/10.1146/annurev.nu.14.070194.002103
  5. Dawson M. I. (2000). The importance of vitamin A in nutrition. Current pharmaceutical design, 6(3), 311–325. https://doi.org/10.2174/1381612003401190
  6. Khan, U. M., Sevindik, M., Zarrabi, A., Nami, M., Ozdemir, B., Kaplan, D. N., Selamoglu, Z., Hasan, M., Kumar, M., Alshehri, M. M., & Sharifi-Rad, J. (2021). Lycopene: Food Sources, Biological Activities, and Human Health Benefits. Oxidative medicine and cellular longevity, 2021, 2713511. https://doi.org/10.1155/2021/2713511
  7. Naz, A., Butt, M. S., Sultan, M. T., Qayyum, M. M., & Niaz, R. S. (2014). Watermelon lycopene and allied health claims. EXCLI journal, 13, 650–660. Retrieved June 9, 2022, from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4464475/
  8. U.S. Department of Agriculture, Agricultural Research Service, FoodData Central (2019). Seeds, watermelon seed kernels, dried. Retrieved June 9, 2022, from: https://fdc.nal.usda.gov/fdc-app.html#/food-details/169407/nutrients
  9. Kaye Foster-Powell, Susanna HA Holt, Janette C Brand-Miller, International table of glycemic index and glycemic load values: 2002, The American Journal of Clinical Nutrition, Volume 76, Issue 1, July 2002, Pages 5–56, https://doi.org/10.1093/ajcn/76.1.5 
  10. Atkinson, F.S., Brand-Miller, J.C., Foster-Powell, K., Buyken, A.E., & Goletzke, J. (2021) International tables of glycemic index and glycemic load values 2021: a systematic review. The American Journal of Clinical Nutrition, 114(5), 1625–1632. https://doi.org/10.1093/ajcn/nqab233
  11. Fedewa, A., & Rao, S. S. (2014). Dietary fructose intolerance, fructan intolerance and FODMAPs. Current gastroenterology reports, 16(1), 370. https://doi.org/10.1007/s11894-013-0370-0
  12. Montford, J. R., & Linas, S. (2017). How Dangerous Is Hyperkalemia?. Journal of the American Society of Nephrology : JASN, 28(11), 3155–3165. https://doi.org/10.1681/ASN.2016121344

About the Author

Julia Zakrzewski Headshot
Julia Zakrzewski is a Registered Dietitian and nutrition writer. She has a background in primary care, clinical nutrition, and nutrition education. She has been practicing dietetics for four years.
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Please note: The Signos team is committed to sharing insightful and actionable health articles that are backed by scientific research, supported by expert reviews, and vetted by experienced health editors. The Signos blog is not intended to diagnose, treat, cure or prevent any disease. If you have or suspect you have a medical problem, promptly contact your professional healthcare provider. Read more about our editorial process and content philosophy here.

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