Can You Eat Onions on Keto Diet? (Well, it Depends)

are onions keto

We know that we need to avoid those pesky carbohydrates, but can you eat onions on keto?

Onions are veggies and veggies are safe to eat during keto diet right?

Well, not so fast.

Onions can be a two-edged sword and in this article, I will go over how to incorporate into your diet.

can i eat onions during keto?

Can you eat onions on keto diet?

Well, it depends. 

If you are just starting out or it’s been 2-3 weeks and you are not completely in ketosis yet, you should not eat onions on keto diet since they will just slow down your progress.

You can eat onions on keto diet once you are fully in ketosis and fat-burning mode, you can gradually start to increase your carb intake, depending on your metabolism and how many calories you spend in a day.

You can consume anywhere from 20-30 grams of ‘net’ carbohydrates per day and still remain in ketosis.

keto friendly onions

Once you are ‘fat adapted’, the best types of onions to consume on Keto diet are:

  • Green onions / Scallions : 4.4 grams of ‘net’ carbs per 100g / 3.5oz / 2/3 cup serving
  • Yellow / Brown onions : 6.1 grams of ‘net’ carbs per 100g / 3.5oz / 2/3 cup serving

These two types are your best bet, although we have more detailed numbers on all onions below!

Using a ketone breath analyzer to check your breath ketone levels is a good way to see if you are on the right track and check how far in ketosis you currently are.

Light ketosis starts at 0.5 mmol/L, with 1.5 – 3 mmol/L being the optimal ketosis range.

  1. But once you are in ketosis, how much onions can you eat daily? 
  2. How much ‘net’ carbs do the other types of onions have?
  3. What are ‘net’ carbs? 

We will answer all of these questions and we also have some bonus tips on how to use onions, so stay tuned!

In the beginning, avoid ALL carbs

hidden carbs keto hunger

It is very important to note that if you are just starting out or you are relatively new to the Keto diet way of eating, you should try your hardest to avoid any carbs possible (including onions, yes).

For all your life up to this point, your body has run on carbohydrate and sugar fuel, so it will take some time until your body becomes “fat adapted” and switches to burning fats for fuel instead.

Usually, when people start a low-carb diet, it takes them about 3-4 weeks to reach “fat adaptation”.

Your mileage may vary, but there are a few things that are very good indicators. 

If you start to experience constant energy through the day, mental clarity and if you are also being able to go through the day for longer periods of time without feeling hungry there’s a very good chance that you are fat adapted!

And if you just want to make sure, there’s always the option to use the before-mentioned blood ketone meters.

How many onions can I eat in a day?

This depends solely on how many grams of carbs your body can tolerate without kicking you out of ketosis.

If you want to eat onions on keto diet, then understand this:

For most people out there, 20 grams of ‘net’ carbs (more on what ‘net’ means below) is kind of the safety net for staying in a state of ketosis.

Now, if your metabolism is fast and if you have intense workout sessions every day,

you can bump that number up to like 40-50 grams of ‘net’ carbs and get away with it.

By the way, if you happen to not know what ‘net’ carbs are, it’s actually pretty simple.

On the nutrition label of almost every product, most often they include the Fiber in the Total Carbohydrates amount so the number can be a bit misleading.

Humans have no digestive enzymes (1) to process most fiber, so it has absolutely no effect on our blood glucose and insulin levels, and because that’s the reason we count carbs:

  1. We want to take the amount of fiber out of the Total Carbohydrates amount listed on the label. 
  2. So let’s say if a product says it has a Total Carbohydrates amount of 14 grams, of which 11 grams is fiber.
  3. We take the 11 grams of fiber out of the 14 grams of total carbs and we are left with only 3 ‘net’ carbs (the ones we care about and count) per serving. 

Now with that out of the way, let’s talk numbers!

Not all onions are the same

Below, we have more detailed ‘net’ carb information on all of the most common onions out there, listed from worst to best respectively in terms of the number of carbohydrates.

#1. Shallots

Like garlic, shallots are formed in clusters of offset with a head composed of multiple cloves. Shallots are extensively cultivated for culinary uses, propagated by offsets.

Per 100g / 3.5oz / 2/3 cup:

Total Carbohydrates: 17 grams of carbsOf which fiber: 3.2gNet carbohydrates: 13.8g

keto onions Shallots

#2. White onions

White onion is a is a cultivar of dry onion, that has a pure white papery skin and a sweet, mild white flesh. Similar to red onions, due to the high sugar content, they have a short shelf life, lasting up to 2 days, or if refrigerated

Per 100g / 3.5oz / 2/3 cup:

Total Carbohydrates: 9.6 grams of carbs    Of which fiber: 1.2gNet carbohydrates: 8.4g

keto onions White onions

#3. Red onions

Red onions are cultivars of the onion and have a mild to sweet flavor. They are high in flavonoids (2), and fiber – compared to white and yellow onions. This makes it a great source of antioxidants, and an anti-inflammatory agent, helping to reduce the risk of certain chronic diseases.

Per 100g / 3.5oz / 2/3 cup:

Total Carbohydrates: 9.7gOf which fiber: 2.2gNet carbohydrates: 7.5g

#4. Sweet onions

A sweet onion is a variety of onion that is not pungent. Their mildness is attributable to their low sulfur content (3) and high water content when compared to other onion varieties

Per 100g / 3.5oz / 2/3 cup:

Total Carbohydrates: 8 grams of carbsOf which fiber: 0.9gNet carbohydrates: 7.1g

keto onions sweet onions

#5. Yellow/brown onions

Yellow onion is a variety of dry onion with a strong flavour. It has a rich onion taste and is fit for many dishes like soups, stews and braises. They can become sticky and sweet when caramelized.

Per 100g / 3.5oz / 2/3 cup:

Total Carbohydrates: 8.1 grams of carbsOf which fiber: 2gNet carbohydrates: 6.1g

keto onions yellow onions

#6. Scallions

Scallions have a milder taste than most onions. Although the bulbs of many Allium species are used as food, the defining characteristic of scallion species is that they lack a fully developed bulb.

Per 100g / 3.5oz / 2/3 cup:

Total Carbohydrates: 7 ​grams of carbsOf which fiber: 2.6gNet carbohydrates: 4.4g

BONUS: Tips on how to use onions during keto

Tip #1. Avoid cutting circles

If you are concerned about going overboard with carbs and you want to use onions for a salad, 

instead of cutting the onion in circles try shredding it instead. The flavor will be much more intense and you won’t need to use as much in terms of quantity.

Tip #2. Don’t cook the hell out of them

Don’t cook them too much.

Some people leave them on the stove for too long and they get overdone and lose all their nutrition. 

So, you want to cook them a little shorter, and also make sure the cooking temperature is on the lower side.

Tip #3. Do not caramelize your onions

Don’t caramelize your onions, a lot of people have reported a lot bigger spikes in blood sugar after consuming caramelized onions versus eating them raw or lightly cooked.

It doesn’t matter that the carb count stays the same,

caramelizing the onions breaks down their connective tissue and fiber, making their glucose way more bio-available for the body.

The takeaway

If you are just starting out on Keto and you are not in ketosis yet, you should be strict and avoid any carbs possible since they will slow you down greatly.

Once you get into ketosis and you are ‘fat-adapted’, you can start to increase your carb-intake gradually and go up to 20-50 grams of ‘net’ carbs per day (on the lower or upper end depending on your metabolism and activity levels).

No matter what foods we are talking about, if you want to find out how much you can eat of a certain thing, all you need to do is decide what your daily allowance of carbs is going to be, take those numbers into account together with the product you want to eat and do some simple math.

If we are talking onions, you best bet are Green and Yellow onions, with the others being in the average range while Shallots are the worst kind and we would never recommend having them on Keto since they are way too starchy.


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