Onion · raw

Raw onion provides about 40 kcal per 100 g, with 1.2 g of protein, 8 g of carbs, 0.2 g of fat and 1.7 g of fiber. A medium onion of 110 to 150 g is therefore barely 45 to 60 kcal. On a plate you rarely use more than 50 g, around twenty calories for a huge gain in flavor, which makes it a quiet ally in any diet.

Its carbs are mostly natural sugars and soluble fibers. The vegetable is high in water, which keeps its energy density low. Since it is usually a seasoning rather than a main dish, what matters is not its macros but what it makes possible: eating more vegetables, lean proteins and legumes without boredom, thanks to tastier dishes.

In practical terms, think in weight rather than in number of onions: a small 30 g portion of chopped onion in an omelet or a sauce adds barely 12 kcal. When you track your macros you can weigh or estimate it without stress, because the possible error is tiny compared with that of a spoonful of oil or a knob of butter.

Onion supplies a little vitamin C, vitamin B6, folate and potassium. It also contains sulfur compounds, responsible for its smell and for the tears when you cut it, as well as flavonoids such as quercetin, mostly in the outer layers. These molecules are the subject of many studies, but the results remain nuanced.

So do not count on onion as a remedy: it is one plant food among others, useful in a varied diet. Red and yellow onions contain more antioxidants than white ones, but the calorie differences are minimal. For a specific medical need, talk to a health professional rather than relying on a single food.

To benefit from the compounds in the outer layers, remove only the dry skin and the first thin layer, and avoid peeling too generously. A short cook keeps more vitamin C, but a long cook makes onion easier to digest. There is no perfect method: choose according to the dish and your tolerance.

When you cook onions, the trap is the oil. One tablespoon of oil adds about 90 kcal, more than two whole onions. Use a non-stick pan, a small spoon of oil or a splash of water or stock, and cover so the onions soften in the steam before browning. The result stays tasty with far fewer calories.

Slow cooking (15 to 40 minutes over low heat) brings out the natural sugars, so onion turns mellow and slightly sweet without added sugar. Cooked onions lose water: 100 g cooked comes from well over 100 g raw, so weigh them raw or log their starting weight in your tracking to stay consistent.

Onion contains fructans, fermentable carbs that can cause bloating and gas in people with a sensitive gut, notably with irritable bowel syndrome. If that is you, cooking sometimes reduces the discomfort, and oil infused with onion then strained gives flavor without the fructans, but talk to your doctor or a dietitian.

For breath and hand odor, lemon, parsley, milk or rubbing your fingers on stainless steel help a little. To cut down on tears, chill the onion in the fridge for 30 minutes before cutting and use a very sharp knife: fewer damaged cells means less irritating gas released.

If you eat raw onion before a session or an appointment, keep the portion modest: a large raw amount can cause burping and strong breath for hours. It is best eaten with a real meal rather than on an empty stomach, and worth testing your tolerance in training before putting it in an important meal.

In a deficit, onion helps you make simple foods like chicken breast, eggs, vegetables or lentils tasty without fatty sauces. Raw in thin slices in a tuna salad, it adds crunch and bite. Roasted in the oven or pan-cooked with a little water, it brings a sweetness that replaces the need for sauce.

For example, the tuna, tomato and cucumber salad gains a lot from a few red onion rings, and the chickpea and tuna salad or the lentil, feta and tomato salad benefit too. These dishes stay high in protein and fiber, so filling, while the onion makes them more appetizing.

To eat a lot, meals need to be appealing, and nearly every base recipe starts with a sautéed onion. It is found in whole-wheat pasta with lean beef and tomato sauce, in beef and egg fried rice and in beef and red kidney bean chili con carne. These recipes combine protein, carbs and some fat for a surplus that is easy to reach.

It is not the onion that makes these dishes calorie-dense, but the meat, starches and oil. It brings flavor, volume and a little fiber. You can therefore add it generously with no notable effect on your calorie total, and focus on the real energy sources on the plate.

Choose firm, heavy onions with dry, papery skin, no soft spots or green sprouts. Store them whole in a dry, dark, well-ventilated place at room temperature, but not next to potatoes, since they spoil faster together. A whole onion keeps for several weeks, even a few months depending on the variety.

A cut onion keeps in an airtight box in the fridge for two to three days. You can also chop and freeze it in portions to save time on your weekly meal prep. Avoid storing it next to aroma-sensitive foods like milk or butter, which absorb smells easily.

For meal prep, cook a big pan of onions at the start of the week and keep it in the fridge in a closed box: you can add it in seconds to eggs, grains or legumes. This small habit saves time and helps you make simple, protein-rich, tasty meals without relying on ready-made dishes.

Common mistakes: burning the onion over too high a heat, which makes it bitter; forgetting the added oil in your calorie tracking; storing it whole in the fridge, where it softens; or avoiding it out of fear of the smell when it makes many dishes easier to eat regularly, legumes for instance.

For ideas, try it in an omelet, in a soup, as oven-roasted onions, as quick vinegar pickles for bowls, or chopped raw into savory skyr with herbs. A red onion marinated 20 minutes in vinegar and a little water lifts any bowl of rice and chicken with almost no calories.