What’s your carb limit on a keto diet, 20g, 30g or 50g?

by | Last updated: Oct 28, 2020 at 6:44AM | - Published on: Jul 1, 2020

By knowing your carb carb limit you can achieve nutritional ketosis, a natural metabolic state that has been strongly linked to improved blood sugar control, fat loss, mood control and more.

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Determining your carb limit on keto for beginners

If you’re just starting out with keto, figuring out your macronutrient ratios can be a bit challenging and potentially daunting. With keto, the standard macronutrient ratios are 70-80% fat, 20-30% protein, and 0-10% carbohydrates. However, depending on your current health status and goals, this breakdown may change. So how do you know what your carb limit and ideal macro intake should be? Keep reading and we will guide you through it.

Carbs and ketosis

Carbs are the big diet switch for ketosis — they can either keep you in a ketogenic state or they can kick you out of it, so knowing which carbs you can and cannot consume is imperative. While carbs are the basis of things like bread, cereal, pasta, pastries, and the like, they’re also in less obvious places like nuts and seeds, fruit, and vegetables.

For most people following a standard American diet (SAD), carbohydrates comprise a large portion of the diet. When we consume carbs, we end up with glucose available as fuel for our cells and normal bodily functions. When blood sugar (blood glucose) levels increase as a result of consuming carbs, the hormone insulin also rises in the blood. Raised insulin signals fat cells to reduce the amount of fat they’re liberating into the blood (lipolysis). The more sensitive the fat cell to insulin and the more insulin your fat cells are exposed to, the easier it is to fatten.

This is why a donut is a good example of a food with dual ‘fattening’ properties: it’s highly insulinogenic due to its refined carbs and contains lots of omega-6 seed oils that sensitize fat cells to insulin. This junk-food double-hit leads to poor insulin signaling, itself a massive contributing factor to obesity and several other chronic health conditions, as well as metabolic syndrome [1].

When following a ketogenic diet, carbs are restricted. This limits the amount of fuel available for glucose-based metabolism. Protein doesn’t often need to be restricted, except moderately so when reaching deeper levels of ketosis. When little to no dietary carbohydrates are available, liver glycogen stores drop down low enough to increase ketogenesis substantially after about 12-16 hours. The absence of dietary carbs leads the body to ramp up gluconeogenesis in order to keep the glucose coming for minimal glucose requirements. The flux of free fatty acids (FFAs) and ketones also increase to meet energy previously met by glucose.

When all of these physiological changes reach a certain threshold – often defined somewhat arbitrarily as > 0.5 mmol/L of betahydroxyburytate in the blood – it is said that one is ‘in ketosis’. By this point, the liver has produced ketones at a substantial rate and the brain has taken them up in step with their ever-increasing blood concentration. Because the absence of refined carbs no longer causes excessively large fluctuations in insulin, the overall exposure to insulin is lower and levels stabilize. Less overall insulin exposure increases fat burning, among many other benefits.

With that said, when carb intake is sufficiently low, the body can more fully rely on the intake of fat for fuel, and thus entering the metabolic state of ketosis. One of the first signs of entering nutritional ketosis is the keto flu — a collection of flu-like symptoms resulting from carb withdrawal and electrolyte loss causing things like fatigue, nausea, headache, insomnia, and diarrhea. If you’re unsure whether or not you’re in ketosis: measure.

How many carbs will kick you out of ketosis?

Naturally, you may be wondering “how many carbs can I have on keto?” The answer to this question isn’t quite as simple as you can only have x grams of net carbs per day; it’s going to range from person to person based and on a few factors. These include:

  • Body composition and weight
  • Activity levels
  • Sleep
  • Stress levels
  • Past dietary habits
  • Age

As a general rule, the more restrictive you are with your carbs, the easier it is to get into ketosis and stay there. If you’re just starting out with keto, it’s more straightforward to just keep your net carb intake around 20-25g; remember that net carbs equal total carbs minus fiber. For most people, 20-25g of net carbs will enable them to reach ketosis. After you’ve been stable in ketosis for a few weeks, you can play around with your carbohydrate intake to see how liberal you can get before leaving ketosis. For most people, using a ketone-glucometer is the easiest way to see how many carbs it takes to kick you out of ketosis or shoot up your blood sugar.

Why do people have different carb limits for keto?

The appropriate carb limit varies somewhat amongst different people. The only way to find out what your carb limit is, is to get into ketosis and test your ketone levels (e.g. with a blood ketone device). By tracking your carb intake, you’ll be able to approximate how many grams of carbs you can eat before dropping below a certain level of blood ketones. Over time, you’ll be able to appreciate how sleep patterns, activity levels, protein intake and stress all play a role in how many carbs your body can handle whilst still being in ketosis.

Your personal carb limit is not only about your own physiology, but also about your goals as an individual. For example, athletes can tolerate a higher carb intake for a given level of ketosis during intense training periods than they can in the offseason. Carb limits can thus vary within the same person in addition to person to person.

Figuring out your carb limit is all about experimentation and tuning into how your body feels. Some people eat less than 50g of net carbs per day right from the start, and they feel like a million bucks. On the other hand, some people feel awful and rather than getting through it they opt for several weeks of slowly ratcheting the carbs down from 100g to whatever level enables them to be in ketosis. It’s important to observe and listen to how your body responds and adjust as needed, not just rigidly apply general recommendations.

What could a self-testing schedule look like? Try to keep your protein and calorie intake equal throughout.

Day 1-5: Consume 20-25g of net carbs for about 5 days.

Day 6-7: Test your ketones after waking up (in a fasted state) for 2 days in a row so you can set your baseline level.

Day +8: You can then add in 10g of carbs every day until you fall below your target level of ketones (e.g. < 2, < 1, or even < 0.5 mmol/L blood beta-hydroxybutyrate). To be thorough you should measure your blood ketones 30 minutes before eating and 1 hour after eating to keep track of your non-fasting ketone levels too.

Keep in mind that the more you can keep other variables the same (e.g. sleep, stress, and exercise) the more reliable your carb limit is.

What do 20, 30 or 50 grams of carbs look like from real food?

You may have heard people reaching ketosis with a 20, 30, or 50-gram carb limit – but were they speaking about the net or total carbs? There’s a difference. The carb limit Nutrita refers to is net carbs, not total carbs. Net carbs are the fraction of carbs that you absorb to use as energy. As such, the higher your net carb limit is, the more flexibility you have with your food choices, within reason of course. The fact of the matter is, 20 grams of net carbs isn’t a lot, especially if you’re incorporating things like full-fat dairy and berries that have carbs, albeit minimal — they add up. But if you’re eating a diet full of high-quality meats, healthy fats, and low carb veggies, your options (and even portions) are far from limited.

Here are examples of what different amounts of carbs looks like:

20g net carb limit

 

Sample 1 day meal plan for a 20g net carb limit

Breakfast (2.9g net carbs)
3 boiled eggs and 200g of (creamed) spinach

Lunch (6g net carbs)
150g of salmon fillet and 50g of fresh blueberries

Dinner (13.9g net carbs)
200g of steak and 145g of carrots pan-fried in butter

30g net carb limit

Sample 1 day meal plan for a 30g net carb limit

Breakfast (10.4g net carbs)
3 boiled eggs and half of a medium apple

Lunch (6.1g net carbs)
5 medium-sized shrimp and 150g of freshly steamed broccoli

Dinner (11.8g net carbs)
150g of octopus and a small sweet potato pan-fried in coconut oil

50g net carb limit

Sample 1 day meal plan for a 50g net carb limit

Breakfast (9.4g net carbs)
3 medium-sized eggs pan-fried in butter and 2 medium red bell peppers

Dinner (39.3g net carbs)
200g of bacon and 50g of white rice

What happens if you eat too many carbs on keto?

Simply put, eating too many carbs will kick you out of ketosis. This would mean moving away from a deeper state of fat-burning to one more reliant on glucose. When people go overboard on carbs, whether on a ketogenic or not, it’s not uncommon for them to encounter

Blood sugar swings [2]
Cravings for sweet foods
Inflammation (e.g. joint pain)
Bloating and other digestive discomforts [3]
Memory impairments [4]

Going over your carb limit with white rice and sweet potatoes is one thing, but doing so with donuts and pizza is another. The latter contains lots of oxidized omega-6 fats (linoleic acid) that will contribute to further unwanted inflammation [5]. Hence, these foods need to be strongly moderated on any well-formulated ketogenic diet.

However, you’ve gone over your carb threshold, getting back into ketosis may be a bit trickier than you thought. Intermittent fasting is one of the best ways to kick up fat burning and get you back on track to ketosis. When your body doesn’t have any fuel coming in, liver glycogen is relied upon while fat burning progressively ramps up [6]. Low liver glycogen stores are a strong signal for returning to ketosis.

Just remember that when you fall off and eat bad food, there’s no benefit to beating yourself up about it. Make note of it as something to avoid in the future, and move on. Get your focus back on quality foods like beef, shrimp, and eggs, rather than the junk-food triad of sugar, flour and high omega-6 seed oils.
Final word
Knowing your personal carb limit for ketosis means you have a great tool at your disposal. You can dip in and out of ketosis as suits you best, and relatively easy with the knowledge of where your threshold lies.

Some people know their carb limit for ketosis and stay under it, others prefer to dip in and out of. Whatever your approach is, knowing this one thing about how your metabolism responds to carbs is valuable.

Final word

Knowing your personal carb limit for ketosis means you have a great tool at your disposal. You can dip in and out of ketosis as suits you best, and relatively easy with the knowledge of where your threshold lies.

Some people know their carb limit for ketosis and stay under it, others prefer to dip in and out of. Whatever your approach is, knowing this one thing about how your metabolism responds to carbs is valuable.

Written by Raphael Sirtoli, MSc Biology

Raphael is self-learner and self-experimenter. A decade before starting on his scientific path he started adopting various low-carb diets and many new lifestyle practices, such as cold exposure, meditation, barefoot running and Wim Hof breathwork.

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