How Many Calories Are in Watermelon? Weight Loss, Diabetes & Nutrition Explained

Watermelon really is the classic summer fruit—sweet, juicy, and hard to resist when it’s hot outside. It’s not just tasty, either. When the sun’s beating down, biting into a cold slice of watermelon actually helps cool you off and keeps you hydrated. Kids love it, adults love it, and honestly, who doesn’t want something light and refreshing when it’s sweltering?

Now, with everyone paying more attention to calories and health, a bunch of questions pop up: How many calories are in watermelon? Is it good if you’re trying to lose weight? Can you eat it if you have diabetes?

Let’s break it all down and see what watermelon really offers—how many calories you’re getting, what’s in it, if it fits into a healthy diet, and the best way to enjoy it.

So, what exactly is watermelon? Technically, it’s called Citrullus lanatus, part of the Cucurbitaceae family (that’s the same group as cucumbers and pumpkins). The thing to know? Watermelon is about 90–92% water. That’s why it feels so light and refreshing—and why it’s low in calories.

 Let’s get straight to the numbers.

How Many Calories Are in Watermelon?

If you scoop out 100 grams of watermelon (which is a decent chunk), you’re only looking at about 30 calories. That means you can fill your bowl without worrying much about your calorie count.

Here’s a quick look at different serving sizes:

100 grams: 30 calories

1 cup (about 150 grams): 45–46 calories

1 medium slice: 80–85 calories

1 full kilo: around 300 calories

Put it this way—a whole kilo of watermelon has about as many calories as a single plate of rice. So, you can eat a lot more watermelon for the same calories.

What else is in watermelon? Here’s what you get per 100 grams:

Water: 91%

Carbohydrates: 7.6 grams

Protein: 0.6 grams

Fat: 0.2 grams

Fiber: 0.4 grams

Plus, there’s vitamin C, vitamin A (from beta-carotene), potassium, and lycopene (that’s the antioxidant that gives watermelon its red color).

Why is watermelon so low in calories? Simple:

First, it’s mostly water, so you fill up without much energy.

Second, there’s almost no fat.

Third, even though it tastes sweet, there’s not a ton of sugar—so it doesn’t sneak in extra calories.

 watermelon is light, hydrating, and easy on the calories, which makes it a great choice if you’re watching your weight or just want something refreshing.

Is Watermelon Good for Dieting?

Absolutely. Watermelon fits right into most diets.

Why Does Watermelon Work So Well for Weight Loss?

It’s low in calories, so you can eat plenty without feeling guilty. It fills you up, too, which helps curb those late-night snack attacks. And because it’s packed with water, it keeps you hydrated. No wonder so many nutritionists suggest adding watermelon to weight-loss plans.

How Watermelon Helps With Weight Loss

1. You Get More, for Less  

You can dig into a generous bowl of watermelon and still keep calories down.

2. Good for Your Metabolism  

All that water and those vitamins help your body run smoothly.

3. Satisfies Your Sweet Tooth  

Craving dessert? Watermelon’s natural sweetness can help you skip the junk food.

Watermelon and Diabetes: What’s the Deal With Sugar?

Some folks worry watermelon is off-limits for people with diabetes. Here’s the truth:  

Watermelon does have a high glycemic index, but its glycemic load is low. Translation? If you stick to a small serving, it won’t send your blood sugar skyrocketing. People with diabetes can usually enjoy about one cup (100–150 grams) a day — just check with your doctor first.

Lycopene: The Bonus Nutrient in Watermelon

Watermelon is packed with lycopene, a powerful antioxidant. Lycopene lowers the risk of heart disease, helps protect against some cancers, and keeps your skin looking fresh. And the best part? You get all these benefits for barely any calories.

When’s the Best Time to Eat Watermelon?

Eat it in the morning, afternoon, after a workout, or even at iftar (just don’t overdo it). Try to avoid loading up right before bed — too much water and sugar late at night can mess with your stomach.

How Much Watermelon Should You Eat?

General adults: 1–2 cups  

If you’re trying to lose weight: 1 cup  

People with diabetes: ½ to 1 cup

Does Watermelon Make You Gain Weight?

Nope. Watermelon isn’t the problem — overeating in general is. You gain weight by taking in more calories than you burn, not by eating watermelon. Since it’s low-calorie, it won’t tip the scales if you enjoy it in moderation.

How Does Watermelon Stack Up Against Other Fruits?

Here’s a quick calorie check for 100 grams of fruit:  

Watermelon: 30  

Apple: 52  

Banana: 89  

Mango: 60  

Grapes: 69

Watermelon is one of the lowest-calorie fruits you can find.

Myths About Watermelon

Myth: “It’s too sugary, so you have to avoid it.”  

Fact: Watermelon’s sugar and calorie content are actually quite reasonable.

Myth: “It makes you hungrier while dieting.”  

Fact: It’s filling and helps keep hunger away.

Things to Watch Out For

Eat too much, and you might get bloated.  

If you have kidney issues, keep an eye on potassium.  

Skip eating big portions late at night.

Watermelon is low in calories, packed with nutrients, and genuinely good for you.

To sum it up:  

Every 100 grams has just 30 calories  

Perfect for weight loss and hydration  

Safe for people with diabetes, in moderation

Want to eat healthier and feel better? Make watermelon a regular part of your diet.

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