Are Yellow Onions High in Calories? The Surprising Truth

November 23, 2025 •

4 min read

Raw yellow onions are remarkably low in calories, with approximately 40 calories per 100 grams, making them a fantastic, low-energy addition to many meals. The question of whether yellow onions are high in calories is easily answered when you look at their nutrient profile, packed with flavor and health benefits without the caloric density of other ingredients.

Quick Summary

Yellow onions are low in calories, offering rich flavor and nutrients without a significant caloric impact. They contain fiber, vitamins, and antioxidants, and their calorie count can change based on preparation methods.

Key Points

Low Calorie: Raw yellow onions contain only about 40 calories per 100 grams, making them a low-energy food.
Preparation Matters: The calorie count can increase significantly if you cook onions with large amounts of oil or butter, so choose low-fat cooking methods.
Rich in Antioxidants: Yellow onions are especially high in antioxidants, such as quercetin, which have anti-inflammatory benefits.
Digestive Aid: As a source of prebiotic fiber, onions support healthy gut bacteria and improve digestive function.
Nutrient-Dense: Onions are packed with essential vitamins like C, B6, and folate, plus minerals like potassium, for a small calorie price.
Versatile Ingredient: Use yellow onions in their low-calorie form by adding them raw to salads or roasting them as a side dish.

Yellow Onion Calorie Breakdown

For anyone monitoring their caloric intake, understanding the energy density of different foods is key. Yellow onions, a staple in many cuisines, are often a subject of curiosity. The simple fact is that raw yellow onions are not high in calories. In fact, they are a low-calorie, nutrient-dense food, perfect for adding flavor to a variety of dishes without adding extra guilt.

Calorie Content in Raw Yellow Onions

According to nutritional data, a 100-gram serving of raw yellow onion contains around 40 calories. This is a very small amount, especially considering the flavor and nutritional boost it provides. To put this in perspective, a medium-sized onion weighs roughly 110 grams, putting its total calorie count around 44 kcal. This low number is due to its high water content, which makes up about 89% of its weight. The remaining calories come from carbohydrates, with tiny amounts of protein and virtually no fat.

How Cooking Affects Onion Calories

While the onion itself is low in calories, the way it is prepared can significantly change its nutritional profile. Sautéing in butter or oil, for example, will dramatically increase the calorie count because fats are energy-dense. Conversely, cooking methods like roasting or boiling with minimal added oil keep the calorie count low. The caramelization process, where onions are cooked slowly to bring out their natural sugars, will concentrate the sugars but the overall caloric increase is modest unless excessive oil or butter is used.

Comparison of Onion Calorie Counts

To provide further context, a comparison table shows how different onion types and preparation methods stack up in terms of caloric density. Data is based on a 100-gram serving.


Onion Type	Preparation	Approx. Calories per 100g	Key Flavor Profile
Yellow Onion	Raw	38 kcal	Pungent, sharp
Yellow Onion	Sautéed (no fat)	40 kcal	Sweet, mellow
White Onion	Raw	36 kcal	Sharp, slightly milder
Red Onion	Raw	44 kcal	Spicy, sweet
Sweet Onion	Raw	32 kcal	Very mild, sweet
Green Onion (Scallion)	Raw	32 kcal	Mild, fresh

Health Benefits Beyond Low Calories

Beyond their low-calorie nature, yellow onions offer a range of health benefits that make them a valuable part of any diet. They are a nutrient-dense food, meaning you get a high concentration of vitamins and minerals for a low number of calories.

Here are some of the key health benefits:

Rich in Antioxidants: Yellow onions, particularly the outer layers, are packed with flavonoids like quercetin, powerful antioxidants that fight inflammation and cellular damage. In fact, yellow onions may contain significantly more antioxidants than white varieties.
Heart Health: The antioxidants and sulfur compounds found in onions may help lower cholesterol and blood pressure, contributing to a reduced risk of heart disease.
Digestive Health: Onions are a source of prebiotic fibers, such as inulin and fructans, which feed the beneficial bacteria in your gut. This can lead to improved digestive health and a stronger immune system.
Supports Bone Density: Some studies suggest that the flavonoid extract from onions may help support strong bones and increase bone mineral density.
Source of Vitamins and Minerals: Onions provide a good source of vitamin C, vitamin B6, folate, and potassium, which are essential for various bodily functions.

Incorporating Low-Calorie Yellow Onions in Your Diet

Given their low-calorie profile and numerous health benefits, yellow onions can be incorporated into your meals in countless ways. They add flavor, texture, and nutritional value without compromising your health goals.

Here are some versatile ways to use yellow onions:

Raw: Finely chop raw yellow onions to add a zesty bite to salads, salsas, and guacamole. This method preserves the highest amount of vitamins and antioxidants.
Sautéed: Create a base for soups, stews, and sauces by sautéing chopped yellow onion until tender and translucent.
Caramelized: Slowly cook sliced yellow onions over low heat to bring out their natural sweetness. Add them to sandwiches, burgers, or pizzas for a gourmet touch.
Roasted: Roast whole or quartered onions with other vegetables to create a flavorful and tender side dish. This method concentrates their flavor while remaining low in fat.
Garnish: Use thinly sliced or crispy-fried onions as a garnish to add flavor and texture to various dishes.

Conclusion

To conclude, the notion that yellow onions are high in calories is a misconception. They are in fact a low-calorie, nutrient-rich vegetable that can be a flavorful and healthy addition to almost any meal. Whether you prefer them raw, sautéed, or roasted, they contribute vital antioxidants, fiber, and vitamins without significantly impacting your daily calorie intake. For weight management or simply for healthy eating, yellow onions are a fantastic and versatile ingredient to keep in your kitchen. For further details on the nutritional breakdown of onions, refer to sources like Healthline.

Frequently Asked Questions

A medium-sized yellow onion, weighing approximately 110 grams, contains around 44 calories.

While raw yellow onions contain some natural sugar, the amount is low. For example, a 100g portion has about 4.2 grams of sugar. When caramelized, the natural sugars concentrate, but the overall amount is not high.

Yes, onions are good for weight loss. They are low in calories and fat, yet add substantial flavor, helping you feel satisfied without consuming excess calories. They are also a good source of fiber, which promotes fullness.

The calorie difference in the onion itself between raw and cooked is minimal. However, the cooking process typically involves adding fats like oil or butter, which will increase the final dish's calorie count.

Sweet onions generally have the fewest calories, with around 32 kcal per 100 grams. White onions are also slightly lower in calories than yellow or red onions.

To keep yellow onions low in calories, it is best to cook them with minimal fat. Options include sautéing in a non-stick pan with a small amount of water or vegetable broth, roasting them, or incorporating them into soups and stews.

Yes, yellow onions are very healthy. They contain more antioxidants, particularly quercetin, than white onions. The health benefits are comparable across different onion types, with slight variations in nutrient concentration.