Watermelon has recently gained popularity as a low-calorie food that may support weight loss. Watermelon is low in calories but high in nutrients like vitamin C and lycopene. Some research suggests that watermelon and its components may boost fat burning, reduce appetite, improve body composition, and support weight loss in various ways. However, evidence is limited and more studies are needed. This article reviews the science behind watermelon’s effects on body weight and explores how it may help with weight loss.
Watermelon nutrition facts
Here are some key nutrition facts about watermelon:
- Watermelon is 91% water by weight, hence its name.
- It contains only 46 calories per cup.
- It provides small amounts of fiber, protein, and micronutrients like vitamin C, vitamin A, and magnesium.
- Its main active plant compounds are lycopene and citrulline.
- Lycopene is a powerful antioxidant that gives watermelon its red color.
- Citrulline helps relax blood vessels and may support exercise performance.
So in terms of macronutrients like carbs, protein, and fat, watermelon is very low calorie. However, it packs various vitamins, minerals, and plant compounds that may provide health benefits.
Watermelon and fat burning
Research suggests that watermelon may promote fat burning in a few ways:
Citrulline enhances nitric oxide levels
Citrulline is an amino acid found in watermelon rind. Consuming it increases blood levels of arginine and nitric oxide, a compound that causes blood vessels to dilate.
This process is called vasodilation. It enhances blood flow, a key factor in exercise performance and fat burning.
In one study, athletes given citrulline before exercise burned more fat during a cycling test. This could be due to citrulline’s nitric oxide-boosting effects.
Cucurbitacin E inhibits fat cell formation
Watermelon contains a compound called cucurbitacin E related to the bitter taste. Animal research shows it may inhibit fat accumulation by inhibiting immature fat cells, known as preadipocytes, from maturing into fat-storing adipocytes.
Human data is limited, but test-tube studies indicate the compound may help prevent fat gain.
Synephrine acts as a stimulant
Watermelon contains trace amounts of synephrine, a compound structurally similar to the stimulant ephedrine.
Like ephedrine, it may raise resting metabolism and stimulate fat breakdown. However, more human research is needed on synephrine’s effects.
Watermelon and appetite control
Limited evidence suggests watermelon may reduce appetite for the following reasons:
High water content is filling
Foods high in water content like watermelon tend to be low in calories yet filling. Their high water content may reduce appetite and give you the feeling of fullness.
One study found that eating foods with high water content like watermelon reduces calorie intake at meals.
Fiber aids satiety
Watermelon provides a small amount of fiber, around 0.4 grams per cup (152 grams). Fiber slows digestion and promotes feelings of fullness.
Low energy density reduces calorie intake
In addition to being over 90% water, watermelon has a low energy density. This means it provides few calories relative to its volume.
Foods with low energy density have been shown to induce greater feelings of fullness and reduce overall calorie intake.
Watermelon and body composition
A few studies suggest watermelon may improve body composition by reducing body fat and increasing muscle mass:
Citrulline improves exercise performance
As discussed earlier, citrulline in watermelon rind may enhance exercise performance by increasing nitric oxide levels and blood flow.
This could potentially improve workout quality during weight training, ultimately enhancing muscle gain.
Cucurbitacin E prevents immature fat cell formation
By inhibiting immature fat cells from maturing, cucurbitacin E in watermelon may help prevent fat accumulation and decrease body fat percentage.
However, direct studies in humans are needed before strong conclusions can be made.
Watermelon and weight loss
Here is a summary of watermelon’s potential effects on weight loss:
- Watermelon is low in calories but high in water and fiber, which may increase satiety and reduce calorie intake.
- It contains compounds like citrulline and cucurbitacin E that may boost fat burning.
- Citrulline also improves exercise performance, which may aid muscle gain.
- By improving body composition, watermelon may support weight maintenance after weight loss.
While these potential mechanisms make sense in theory, limited evidence exists. Below are the main studies that indicate watermelon or its components may aid weight loss.
Human studies
In one study, adults with overweight and obesity were instructed to eat 2 cups (300 grams) of watermelon per day as part of a hypocaloric diet for 6 weeks. They lost significant amounts of body weight, body fat, and belly fat compared to the control group.
In another 6-week study, athletes given citrulline supplements before exercise lost more body fat than those provided a placebo, despite no changes in calorie intake. This may be due to enhanced nitric oxide production and fat burning from citrulline.
Lastly, a study in 42 women found those given a beverage containing watermelon juice concentrate had increased fat burning during exercise compared to a placebo beverage.
Animal studies
Rat studies show impressive benefits for watermelon intake and body fat reduction:
Rats fed feed supplemented with watermelon or watermelon juice gained less body weight and had decreased body fat than a control group.
Rats fed cucurbitacin E from watermelon juice had reduced fat accumulation in fat cells, a result that researchers attributed to cucurbitacin E.
Mice fed freeze-dried watermelon saw reduced body weight and fat accumulation compared to obese mice not fed watermelon.
However, keep in mind that animals differ from humans in many ways, so studies in rats and mice do not always translate to the same results in people. More human research is needed.
Other potential health benefits
Aside from possible weight loss benefits, watermelon and its plant compounds may offer additional health effects:
May improve heart health
Watermelon provides citrulline, which may increase nitric oxide levels, reduce blood pressure, and improve other risk factors for heart disease.
May support blood sugar control
Animal and test-tube studies indicate compounds in watermelon like lycopene may help reduce insulin resistance and lower blood sugar levels.
May prevent inflammation and oxidative damage
The antioxidants lycopene and vitamin C in watermelon may protect cells against damage from reactive molecules and inflammation.
May boost immune function
Vitamin C in watermelon contributes to immune defense by supporting the function of white blood cells involved in detecting and eliminating pathogens.
Tips for incorporating watermelon into your diet
Here are some tips for adding more watermelon to your diet:
- Enjoy watermelon sliced or cubed as a snack or dessert.
- Blend watermelon with Greek yogurt and mint or basil for a cold soup.
- Pair cubed watermelon with feta cheese and mint for a salad.
- Grill watermelon wedges as an alternative to meat.
- Add diced watermelon to fruit salads.
- Blend watermelon with other fruits into refreshing smoothies.
- Make watermelon rind pickles.
- Mix watermelon juice with lime juice and mint for an antioxidant-packed drink.
Focus on consuming the watermelon flesh rather than the seeds. Additionally, watermelon rind contains more citrulline than the flesh, so consider juicing or pickling the rind.
Potential downsides to eating watermelon
Watermelon is generally safe, even in large quantities. However, some downsides and precautions exist:
- Gastrointestinal issues. Eating large amounts may provoke diarrhea or bloating in some people.
- Allergies. Watermelon may trigger allergic reactions in those sensitive to certain compounds.
- High glycemic index. Watermelon has a high glycemic index, so large portions may spike blood sugar levels.
- Pesticide residues. If conventionally grown, watermelon may contain pesticide residues.
Additionally, watermelon is not a good source of protein, healthy fats, or other essential nutrients. For balanced nutrition, be sure to enjoy watermelon alongside more nutritious foods.
Should you eat watermelon for weight loss?
Here is a final overview of watermelon’s effects on weight loss:
- Watermelon is low in calories and high in water and fiber. It may increase fullness and reduce calorie intake.
- Compounds like citrulline and cucurbitacin E may boost fat burning.
- There’s some evidence that watermelon improves body composition by decreasing fat mass.
- Human studies link watermelon intake with reduced body weight and body fat.
- However, current research is limited to a small number of studies.
- More human research is needed to make definitive claims.
Overall, incorporating watermelon into a weight loss diet may aid your efforts by promoting fullness, enhancing fat burning, and improving body composition.
However, weight loss ultimately requires a sustained calorie deficit. So for the best results, pair watermelon intake with reduced calorie intake and increased physical activity.
At the end of the day, watermelon is best seen as a beneficial addition to a well-rounded weight loss plan — not a magic solution.
The bottom line
Watermelon is a low calorie, highly hydrating fruit rich in nutrients like vitamin C and lycopene. It contains compounds that may boost fat burning, curb appetite, and improve exercise performance.
Human studies link watermelon consumption with fat loss. However, research is in its early stages, and watermelon alone is unlikely to lead to significant weight loss.
That said, watermelon makes a healthy addition to a weight loss diet. Try incorporating watermelon into your meals and smoothies to enjoy its potential benefits for body composition as part of an overall healthy lifestyle.