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All You Need to Know About Carbs on a Low-Carb Ketogenic Diet

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When it comes to ideal carbs intake, I've discussed it in my post here: How Many Carbs per Day on Low-Carb Ketogenic Diet? However, daily carbs intake is not the only aspect you should focus on.

Does Our Body Need Carbs?

It's a common misconception that our body — especially our brain — needs carbs. In fact, the brain can either use glucose or ketones. When you restrict the intake of carbohydrates, your body will switch to using ketone bodies instead of using glucose. Not only that, ketones are a better fuel for our body and brain than glucose, even for highly active individuals. Once you get keto-adapted (3-4 weeks), you will experience improved energy levels. Although a small amount of glucose is still needed, our body can produce glucose on demand via gluconeogenesis.

Dr Volek and Dr Phinney, The Art and Science of Low Carbohydrate Performance (2012):
"Ketone bodies are an important lipid-based fuel, especially for the brain, when dietary carbohydrates are restricted."

It has been estimated that about 200 grams of glucose can be generated daily just from protein (Dr Briffa, Escape the Diet Trap, 2012). Our body needs some glucose (for the red blood cells and portions of the brain and kidney that can’t use ketones) but according to Dr Volek, it's a very small amount. As I said in my post here, there is no need for everybody to follow a very low-carb / "zero-carb" diet and you may need to adjust the level of carbs to fit your needs.

Types of Carbs in Ketogenic Diets

Generally, you should avoid any sugary or starchy foods. The best measure to represent "good" and "bad" carbohydrates is their Glycemic Load (GL), which measures how much insulin will be released by your body for a given food measured in standard portions. This is different to Glycemic Index (GI), which doesn't take the serving size into account. As a result, some foods with a high GI could have a modest GL. Therefore, Glycemic Load is recommended as the best measure for carbs. Most of your carbs should come from non-starchy vegetables (leafy greens, cruciferous vegetables such as broccoli, zucchini, etc.) and nuts.

One of the exceptions where high GI/GL food is recommended is on Targeted Ketogenic Diet (TKD).

According to Lyle McDonald in his book "The Ketogenic Diet":

"Although experimentation is encouraged, most individuals find that 25-50 grams of carbohydrates taken thirty minutes before a workout enhance performance. The type of carbohydrate consumed pre-workout is not critical and individuals are encouraged to experiment with different types of carbs. Most seem to prefer easily digestible carbohydrates, either liquids or high Glycemic Index (GI) candies to avoid problems with stomach upset during training. A wide variety of foods have been used prior to workouts: glucose polymers, Sweet Tarts, bagels, and food bars; all result in improved performance."

Total Carbs vs Net Carbs

A frequent question amongst low-carb dieters is: Should fiber be included when counting carbs?

Let's look at the evidence: Although some soluble fiber may be absorbed, humans don't have the enzymes that could digest most fiber and derive any calories from it. As a result, fiber does not significantly affect blood sugar and ketosis. In general, you can either aim for 20-25 grams of net carbs or ~ 50 grams of total carbs as recommended by Dr. Steve Phinney and Dr. Jeff Volek.

When fiber is not included, the derived carbohydrate values are known as net carbs. Using net carbs reduces the impact of high-fiber foods (vegetables, nuts, etc.) and you can include them in your diet. This turns out to be an argument against those that criticize low-carb diets for the lack of fiber. It's important to stress that fiber doesn't negate carbs - it's simply not counted; so mixing flax meal into a bowl of pasta won't work! You can read more about total vs net carbs in my post here.

Here is the catch: When it comes to food labeling, in countries like US and Canada, carbohydrate values also include fiber (i.e. total carbs). These countries use the indirect method of calculating carbs which means that carbs are calculated "by difference" after they measure protein, fat, water and ash per 100 grams. To get the value for net carbs, you will need to subtract fiber from total carbs. However, this food labeling doesn't apply universally. In other places like Europe, Australia and Oceania, it's common to exclude fiber. They use the direct method of calculating carbs, and therefore "carbs" on food labels refer to net carbs. Keep in mind it doesn't matter where a certain product is sold but where it's imported from.

All You Need to Know About Carbs on a Low-Carb Ketogenic Diet

How can you be absolutely certain about the number of net carbs? Here are 3 simple rules to follow:

  • total carbs can never be lower than fiber
  • total carbs minus fiber can never be less than sugar (net carbs = sucrose + lactose + other sugars + starch)
  • total kcal = calories from fat + calories from protein + calories from carbs (without fiber)

Thankfully, you don't need to do the math yourself. You can use this Hidden Carbs Calculator to find out.

How Many Carbs Per Meal to Avoid Blood sugar Spikes?

We are all different and what is too much for you, may not be for someone else. The best way to find out is to monitor how you feel. If you feel tired and sleepy after a meal, you likely had too many carbs and are experiencing the effects of elevated blood sugar and insulin: an increase in neurohormones that cause drowsiness. The trouble is that with elevated blood sugar, you will soon become hungry and eat more than usual. Unless you eat extra carbs as part of TKD, you should avoid eating too many carbs. Some people can't eat more than 10 grams of net carbs per meal, while others don't experience any significant insulin spikes at a much higher level such as 50 grams of net carbs.

My personal carb tolerance is quite high but I avoid using certain foods such as tropical fruit and even some low-carb sweeteners like Xylitol. Apart from potentially causing terrible digestive issues, Xylitol is not zero-carb and may affect your blood sugar. I prefer to use Erythritol or stevia which have very few carbs. Having said that, not all people have issues with Xylitol. For more about sweeteners, check out my post Complete Guide to Sweeteners on a low-carb Ketogenic Diet.

"Zero-carb" Products and Marketing Tricks

Some brands of low-carb foods use misleading labels such as, "carbs-free", "low-carb" or "zero-carb". You have to be extra careful when buying products like that. Apart from pure fat and meat, there is nothing truly zero-carb. It's not a secret that Atkins products and many others use effective and deceptive marketing tricks. Their products often contain sorbitol, maltitol and other types of sugar alcohols that are associated with insulin spikes and raised blood sugar levels. The paradox here is that even Dr. Atkins in his 1999 edition of "New Diet Revolution", said that "Sweeteners such as sorbitol, mannitol and other hexitols (sugar alcohols) are not allowed."

According to Dr. Andreas Eenfeldt (also known as Diet Doctor), there are more than just Atkins Fairy Tale Cookies to avoid: Julian's Bakery Bread and Dreamfields Low-carb Pasta can be added to the list.

In summary, make sure you always opt for real unprocessed food and avoid prepared meals full of additives and deceptive labelling.

All You Need to Know About Carbs on a Low-Carb Ketogenic Diet

Carbs Before or After Exercise?

If you are physically active, you can try TKD (Targeted Ketogenic Diet) and have small snacks before your workouts. If you are doing lower intensity activity such as walking or light cycling, you won’t probably need any pre-workout meal. While carbs (or even coconut oil) before exercise can improve your performance, carbs after exercise have a different effect.

Whether or not you eat carbs after exercise depends on your goals:

Weight Loss

If you want to lose body fat, you should avoid post-workout carbs. You probably have enough fat tissue for energy. Losing fat may be difficult even on a low-carb ketogenic diet. Check out my post here: Not Losing Weight on Low-Carb Ketogenic Diet? Don’t Give Up and Read Further

Weight Maintenance

If you want to maintain your weight, you won't need any post-workout carbs unless you did a really intense exercise for an extended period of time.

Weight Gain

If you want to gain weight (muscles) or you are a bodybuilder, you can either follow a standard keto diet or add post-workout carbs. You can try pumpkin, sweet potato, root vegetables, berries, banana, etc. You can find more about CKD (Cyclic Ketogenic Diet) here.

The effect of eating carbs strategically is simple. Any carbs consumed raise your insulin level which normally leads to increased energy levels or storing fat. Here is a short video in which Jennifer Elliott, an Australian dietitian, explains such effects of insulin. However, post-workout carbs may have an anabolic effect and stimulate muscle growth (depending on the workout and intensity). This doesn't mean that you need to eat carbs if you want to gain muscle. Unless you aim for a significant muscle gain, post-workout carbs are not needed.

You can read even more about carbs and exercise nutrition in this post: Ketogenic Nutrition and Exercise: Carbs

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Martina Slajerova
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Martina Slajerova

I changed the way I ate in 2011, when I was diagnosed with Hashimoto’s, an autoimmune disease that affects the thyroid. I had no energy, and I found it more and more difficult to maintain a healthy weight.

That’s when I decided to quit sugar, grains, and processed foods, and to start following a whole-foods-based ketogenic approach to food.

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Comments (90)

Does anyone know if ThinSlim foods are truly low carb or am I getting ripped off AGAIN.

Hi Jim, I'd personally avoid it. I had a quick look at their bread and there's wheat gluten, oat fiber and cornstarch. Even if the carb count is low, these ingredients should not be part of a healthy low-carb diet.


I love your Beginners Ketodiet cookbook and make the crackers often. I make quite a few of your dishes often.
I was wondering about negative net carbs though, especially with seeds.
If something has 2.4g carb of which 1.8g is sugar and fibre is 5g- what is the net carb of that 30g serving?
Can someone help please?

Hi Marnie, thank you so much for buying my book and I'm sorry to have missed your comment!
So if something is 2.4 g total carbs and also lists 5 g fibre, it means you are looking at a different labelling. Completely different to the US, in countries like the UK, "carbs" or "total carbs" as labelled actually represent "net" carbs (the term "net carbs" is not used there). So what you need to do is you need to add the fibre to get true total carbs. Here's more: Total Carbs or Net Carbs: What Really Counts?

Thank you very much for your discussion on Keto diet and subsequent information.  It has been very useful.  I am thrilled to have found your site.

Thank you for your kind words, Kim!

I usually have gluten-free oatmeal and a matza that equals 44 g. of carbs. per day. Everything else is greens and oils.  Can I have these two grains or it is just not allowed in a Keto diet?  Thank you.

I'm afraid not. If you want to follow a keto diet, you'll need to give up grains altogether. Here's more information: Complete Keto Diet Food List: What to Eat and Avoid on a Low-Carb Diet

I really liked this article, I am about to start on Keto and truly looking forward to it.
I have two questions though for  those counting their macros.
If you end up with 50 g of total carbs but let's say net carbs would be 10g (if that's possible) is that a bad thing?
Is it more important to total of 50g carbs from different sources or should the focus be on reaching 25-30 net carbs?
If an avocado has 12 g of total carbs and 10 g of fibre, which means 2 net carbs, do you write that you had 2 g of avecado or just write 12 g and have the 2 in the back of you mind?

I think you should be focusing on "net" carbs rather than total carbs - you can find all about this topic here: Total Carbs or Net Carbs: What Really Counts?
If most of it is fibre than the net carbs will be very low. Keep an eye on products that label "net" carbs as they are often mislabeled and the actual effective carbs may be higher.

Good article though inconclusive in the end.
One thing though. Xyletol has no actual carbs and has no impact on insulin. NONE,, zero. I actually determined this by blood ketone measurements for up to 12 hours post consumption on several clients and myself. It's a sugar alcohol. Which isn't equal to carbs. So, 0 carbs.
But there may be a caveat.
Digestively speaking it's a matter of the body getting used to it. It's by far the best sugar substitute for keto. Unless it's mixed with maltodextrin or other filler which, by the way , erythrol usually is. Erythrol is also a sugar alcohol and has  near identical impact on digestion as Xyletol as any other sugar alcohol does. Issues with SAs and insulin is most often in purity..
So maybe, when estimating how sweeteners impact insulin, it would be better to shy away from making broad statements especially when they're likely not applicable to all people.
For example many people get migraines from too much stevia. I stumbled upon this in a personal experience and then researched furher.
Many swear by heart they get kicked out of ketosis by it. I don't for example.
It doesn't mean everyone experiences the same problem and innacurate information steers people in wrong directions. Much is up to self testing.
Last night I had two tablespoons of xyletol in an avocado-walnuts-cocoa shake. My blood ketone levels were much higher after consuming it than before. And this morning even higher.

Thank you for you insights. GI of Xylitol is 13, as compared to Erythritol which is 0 so it is not true that Xylitol has no effect on blood sugar. It may not affect you in the amounts you are using it and it is a good low-carb option but not the best option. This is definitely down to individual tolerance but based on my experience, Xylitol is more common to cause digestive issues. That is the reason I personally avoid it - or use it in small amounts. I don't have the same experience with Erythritol. As explained in this post, others are absolutely fine with Xylitol and can use it without any issues. The impact of sweeteners is explained here: Complete Guide To Sweeteners on a Low-Carb Ketogenic Diet
As another example, apart from a few people (including my partner), IMOs affect most people in terms of raised blood sugar (including me) and are not a suitable low-carb sweetener. I agree that self testing is the best approach when choosing the right sweetener. Better safe than sorry, especially with sweeteners.
Lastly, rather than measuring ketones, it's better to measure blood sugar when assessing the effect of foods. Blood ketone levels show how much you have in your "fuel tank" rather than showing immediate effects of foods you've consumed. Blood sugar levels do not always correlate with ketones - not in the same way: Product Review and Giveaway: Sukrin
As you can see in the chart from the link above, while I experienced a significant blood sugar spike 30 minutes after consuming IMOs (Test 1), I barely saw any effect in blood ketones. There was a change but it was relatively insignificant as it's normal to see a drop in ketone levels after (most) meals.

So I'm confused as to why total carbohydrates matter at all in the keto diet?  Why do I have to keep total carbs at 50 with net carbs at 20-25?  If I'm eating really high fiber foods like vegetables and my total carb is 60 but my net is 25, does it matter?  

Hi Valerie, you don't have to count fibre - I hope this helps: Total Carbs or Net Carbs: What Really Counts?

To preface, I am new to the Keto diet.  However, as per this article, " can either aim for 20-25 grams of net carbs or ~ 50 grams of total carbs".
This means your net carbs should be around 25g OR 50g total.  So, if you eat a bunch of foods that don't have any fiber, then the goal is to not exceed 50g total carbs.  If you are eating a good amount of fiber, then your total carbs, in theory, could be 100g (as long as you consumed about 75g of fiber, of course).  
I may be wrong, but that is how I understand it.  Good luck!

Hello! I love all your post! So much info! I was wandering about potassium and carbs, even on days I eat tons of spinach, cauliflower, raw cacao and pork I can't reach more than 3500mg (with 21g of net carbs), when the amount recommended is 4700. In my country we don't have access to potassium supplements so is even more complicated. How can I eat more potassium and don't go to much up on carbs? (I don't eat sea food or avocado's can't tolerate). I have access to Mccormick salt substitute, but it doesn't say the amount of potassium so I don't know how much to use to make an electrolyte drink. Can someone help me?

I am just starting out on the keto diet.  At first I thought I understood how to count my carbs... but I am getting myself confused.  Easy I ate a salad consisting of 4 oz chicken breast, 6 oz green leaf lettuce, 6 oz. broccoli,1 oz cream cheese and full fat ranch dressing...
I am coming up with 28 g protein...8 g carbs...and whatever the 2 Tbsp of ranch would be... My question is that on the carb side of things it gives the net carbs and the protein for a certain vegetable... Do I count the protein of the vegetable and add it to my meat protein??  I am so confused..

You said: "Some people can't eat more than 10 grams of net carbs per meal, while others don't experience any significant insulin spikes at a much higher level such as 50 grams of net carbs." Wondering why you're using grams. Isn't the GI of the carb what drives the size of the insulin spike? Thanks!

So is it just the sugars that I count as Net carbs if I'm in Australia which is based on the UK breakdown of carbs in food labelling

Dear US food people, total is always higher than net.  Net = total - fiber.  Setting a 20g TOTAL carb goal is more restrictive than a 20g NET carb goal.  Hopefully if you're bad at word problems like me, this helps.

I was wondering if there is a difference between fiber and dietary fiber? Everything I read to subtract says “dietary” but doesn’t say anything regarding the differences.

Question! I've been on the keto diet for awhile; love it. How does one balance carbs and fat. For instance, if keto is supposed to be low carb and high fat, but one can eat avacado *which is both*, how does one balance that? Or can you just scarf down a whole avacado and count it as good fat? I find no explanations.

I have perfect weight according to my height. But the body fat percentage is 30% mostly concentrated in the tummy area. I do cardio for 10-15 min, weights and core exercises. I am also following keto diet since a month and strictly not including any carbs. Do you recommend including little amount of carbs in my pre- workout diet ?
Also will keto diet help in getting rid of my belly fat? And how much time approximately will it take?

"As a result, fiber does not significantly affect blood sugar and ketosis. In general, you can either aim for 20-25 grams of net carbs or ~ 50 grams of total carbs as recommended by Dr. Steve Phinney and Dr. Jeff Volek."
This is confusing. If for the purposes of ketosis net carbs have the same effect on blood sugar as total carbs, why wouldn't the recommendation be to aim for 50 grams of net carbs (same as total carbs). The Jeff sounds like he is hedging bets. What I get from this is net carbs don't have impact but consume less of them just to be safe? This doesn't clear anything up.

What happen if i dont reach net carb of 15-20 gram per day? Because there was a day that i dont even reach 5 gram net carb .

You don't have to reach them - is is a limit, not a target 😊

What fruits are still acceptable when going keto?

Most fruits are not but some are included - have a look at this list: Complete Keto Diet Food List: What to Eat and Avoid on a Low-Carb Diet

I have a quick question.    If the goal of using keto is to lose weight by using my excess body fat then why is such a high percentage of fat part of the keto diet?    It seems counter-intuitive.

Hi Dave, although calories do matter, they are not equal (in a high-carb vs high-fat diet). A diet that is high in fat, moderate in protein and low in carbs has natural appetite suppressing effects. Although a ketogenic meal contains more fat, you will feel less hungry and will stay full for longer. To learn more: How To Start Keto: All You Need To Know

I believe the simple answer is that when you eat fat, it doesn't get stored in your body as fat.

Hello, I have a question.
I understand that total amount of carbs labeled by the companies is being calculated by subtracting fat, protein and in some cases fiber. And net carbs should be calculated by subtracting fiber from total carbohydrates. Now there's a question.
Lets take almonds for example. They have:
Carbohydrate 22 g  
Dietary fiber 12 g  
Sugar 3.9 g
So net carbs for 100 grams of almonds we have 10 grams of carbs.
Usually net carbs include sugars and starch. In the case of nuts there's no starch involved. So what's the rest of 6.1 grams of carbs that we have?
There are many foods that have similar count and i just simply can not find any answer on my question.
Thank you.

Hello Kateryna, net carbs in this case are 10 (it's total carbs minus fibre), where sugar is included in the net carbs. Net carbs refer to carbohydrates that affect blood sugar. There are many types of carbohydrates - this Wikipedia article explains more:

I am in my 2nd week and no longer losing much weight, so I decided to test my ketones levels via a urine strip. The color came back as large amounts of ketones. Am I sabatoging my weight loss by eating to little carbs? I am keeping it between 20-27 grams of net carbs per day.
TIA for any advice!

Hello, I am a bit confused on net carbs when the fibre is more than the carbs.
For example: -
The carbs are 7.3g
The fibre is 38.1g
So the net carb is a negative amount?
Can you help to explain.  Thanks 😊

This is the case of UK labelling - have a look at the "Total carbs vs Net carbs" part of this post 😊

Hi there,
Just wondering, when using MFP to track macros on a keto diet - do you count green veggies towards the total carb count or can you eat as much green as you like?

Hi Jo, you need to track all carbs (net carbs) - our KetoDiet app tracks both total and net carbs using an accurate database. As far as I know, MFP and other similar apps use a "shared database" which is created by their users and it's not verified. This means that in such apps, you will likely find duplicates and inaccurate entries. Here's our food list to help you make the right choices (includes carb count in common foods): Complete Keto Diet Food List: What to Eat and Avoid on a Low-Carb Diet

I'm not trying to lose weight, i'm at a decent weight but I want to use a potentially healthier fuel for my body than glucose. I'm not a small guy in terms of height and frame, i'm also young and physically active. Now with all this count the carbs in your food advice, or count the net carbs in all foods, or Mark's Daily apple advice to consider all non starchy veggies as free of carbs I find it's impossible to hit enough calories without giving up veggies or getting my veggies and calories but too much carbs balance, is there lee way if you're bigger framewise and have a faster metabolism? If so Mark's approach seems better for me, I lose weight if i'm not getting 2400 cal minimum a day not including exercise days. It seems most keto guidelines are for women and small men.

Hi Dave, you can maintain or even gain weight on a keto diet by adjusting your fat intake. I'm  not sure I understand - do you find it difficult to get enough calories with or without veggies? There are some high fat foods that will help you get enough calories (avocado, coconut butter, any nut or seed butter and whole nuts, fatty meat cuts, full-fat dairy, etc). Here's more about total vs net carbs: Total Carbs or Net Carbs: What Really Counts?

I have been cutting out carbs for the last 7 weeks. Have gone from 16'7 down to 14'11. problem I have is for the last week I have stopped losing weight.
I have 2 x Bacon, 2 sausages and 2 fried eggs every morning, Lunch I have 3 boiled eggs and dinner is a mixed grill meat only.
What am i doing wrong, carried out a Keytone test and the colour never changed.

Hi Mark, have a look at this post: How To Low Carb: 15+ Common Weight Loss Mistakes

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