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 (e.g. for the thyroid health) 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 high GI could have low 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 taken into account, 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.
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 = sugar + lactose + other sugars)
- 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 insulin 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 an insulin spike. 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 "carbs tolerance" is quite high but I avoid using certain foods such as tropical fruit and even some low-carb sweeteners like Xylitol. Apart from causing terrible digestive issues, Xylitol is NOT zero-carb and affects blood sugar. I prefer to use Erythritol or stevia which have very little carbs. For more about sweeteners, check out my post Complete Guide to Sweeteners on a low-carb Ketogenic Diet. However, not all people have issues with Xylitol. To read more about sugar alcohols and how they affect blood sugar, have a look at this article at Mendosa.com.
"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 other 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.
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:
If you want to lose fat, you should avoid post-workout carbs. You probably have enough fat tissue for energy that can be converted into muscles. 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
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.
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 muscles. 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