To maintain ketosis, we need to substantially limit the carbs we eat. Ideally we should eat less than 20 grams of net carbs. Exactly how much depends on each individual person and many people will maintain ketosis even when they eat up to 50 grams of carbs.
When you start out, go as low as possible and work out over time what works for you and how many carbs you can consume and still remain in ketosis.
In this article we want to take a closer look at carbs to understand the different types and what they do in our bodies. With a better understanding, we can make better decisions.
First we look at carbs as per their traditional classification of simple and complex. Then the more recent classification based on the glycemic index and load. Lastly we look at what carbs to eat and what not to eat.
Types of Carbs
Carbohydrates are biomolecules or saccharides. In simple terms, carbohydrates are sugars.
There are two types of carbohydrates. Traditionally they were classified as simple and complex.
Simple carbs are made from only one or two sugar (saccharide) chains. All simple sugars and starches convert to glucose in the body. The only exceptions are sugar alcohols and insoluble fiber.
Types of Simple Sugars
- Sucrose is cane or table sugar and all items made from it.
- Glucose is found in starchy vegetables.
- Fructose is the sugar found in fruits and honey. It is very sweet and therefore it is commonly used in many processed foods.
- Galactose is the natural sugar found in dairy products.
Natural and Added Sugars
Naturally occurring sugars are those sugars that are naturally found in food like fruit, vegetables and milk.
Added sugars refer to those sugars added during manufacturing and cooking. These include corn syrup, table sugar and honey. Sugar has many names, so carefully study all labels.
Simple Carbohydrates Include:
Non-starchy vegetables and processed flours as well as all foods made with processed flour. It also includes table sugar and everything made with it, candy, sweets, soda, juices, fruit, milk, honey and syrup. This is not an inclusive list, but you get the point.
Simple carbs, with the exception of non-starchy vegetable, require no break down as they enter the body. They digest quickly and are instantly absorbed to flood the bloodstream with glucose. This then cause a spike in insulin.
This then triggers the release of insulin from the pancreas. Sugar is used where needed and the rest is stored as fat.
The continuous production of insulin may eventually lead to weight gain, insulin resistance and ultimately to type 2 diabetes.
A complex carb consists of sugar molecules that are threaded together in a complex chain.
Foods like peas, beans, corn, potatoes, rice, grains and bread are Complex Carbohydrates.
The insulin response with some carbs may be less severe than with sugars and simple carbs.
However, both provide the body with a fuel source that can turn to stored fat and therefore on a strict ketogenic diet, they are both limited or eliminated altogether.
GI and GL Classification
The classification of carbohydrates as simple and complex does not tell the whole story. This is why we also want to look at the glycemic index and glycemic load of carbohydrates.
The Glycemic Index
The Glycemic Index (GI) is a scale of 1 to 100 that measures how any food will impact blood sugar. A score of 100 represents pure glucose. So the higher the GI of a food, the more it will raise blood glucose levels.
More often than not, complex carbs have a higher GI than simple sugars. But the GI is also influenced by how much the food has been processed and the cooking process.
As an example a baked potato that is a complex carb has a much higher GI than an apple which is a simple carb.
Foods with a high GI tends to release more insulin than low GI foods.
Generally a food with a GI of less than 55 is seen to be low and higher than 70 to be high.
What is Glycemic Load?
Glycemic load (GL) estimates the impact of a specific serving of carbohydrate consumed on blood sugar.
It is calculated by taking the grams of actual carbohydrates (minus water for instance) times its GI score divided by 100.
For example watermelon has a high GI, but because it contains a lot of water its GL is much lower.
Generally a food with a GL of less than 10 is seen to be low, 11 to 19 medium and higher than 20 to be high.
Why does it matter?
The GI or GL of a carbohydrate is a more valuable indication of its impact on blood sugar and insulin than purely whether it is a simple or a complex carb.
The Nurses Study
The Nurses study is a famous long term study that commenced in 1976.
It is the largest epidemiological study conducted in the US into the risk factors for major chronic diseases in women.
75,521 women aged 38 to 63 who had no previous diagnosis of diabetes, angina, myocardial infarction, stroke, or any other cardiovascular conditions were followed for ten years (Liu, S., Willett, W.C., Stampfer, M.J., et al).
After the 10 year follow up 761 nurses had heart disease. Dietary glycemic load was found to be directly associated with risk of cardiovascular heart disease even after risk factors for heart disease were accounted for.
Generally, sugar alcohols are not insulin triggers. Therefor they are not counted as impact carbs (net carbs) in a keto plan.
Some however have a higher GI and they should be carefully monitored for their impact on your individual results.
The reason why they can cause a different impact for different people is because how they are consumed as well as the gut enzymes available to break them down.
Here are the most sugar alcohols and their respective GI:
Effect of Carbs on Ketosis
The conclusion is that all carbs, both simple and complex, no matter the GI load ultimately convert to glucose in the body.
This glucose is used as fuel and energy for cells and other organs inside the body. If there is too much glucose it gets stored as fat.
Reducing Carbs to Induce Ketosis
Normally, the body uses carbohydrates as fuel. With a ketogenic diet the objective is to change the source of energy from carbs to fat. This is achieved by substantially reducing the amount and type of carbohydrates that we eat. And off course to eat more good quality fat. But for now, let’s focus on lowering carbohydrates.
When we adopt a ketogenic lifestyle we limit carbs to non-starchy vegetables that grows above the ground.
We are particularly strict with how little carbs we eat when we start out as the aim is to exhaust the glycogen supplies and start burning fat and thereby trigger ketosis.
Now you may tell me that vegetables are simple carbs and you were always told to eat more complex carbs.
Yeah I know, but non-starchy vegetables:
- Are low in carbs
- Are nutrient dense
- Do not trigger insulin
- Have a low Glycemic load
… and therefore support the aim to trigger ketosis.
- Most vegetables that grow above ground.
- Fruits with very low sugar content like berries.
For a comprehensive shopping list of all foods allowed on the ketogenic eating plan check out our list here.
Carbs to Avoid
- All products made from sugar or with added sugar
- High fructose corn syrup
- All products made from high fructose corn syrup or with added high fructose corn syrup
- Processed foods
- Grains and starches like rice, pasta, oatmeal, couscous and quinoa
- All products made with grains and starches like bread and pizza
- White and sweet potatoes
- Starchy vegetables like peas, corn and root vegetables
- Any other starches
- Sugary and artificially sweetened drinks
You want to lower your carb intake, but you do not want to cut out vegetables all together. You need vegetables for many reasons, but in part they help to keep cholesterol under control and provides many vitamins and minerals.
For more on why you should make sure that you eat enough vegetables, watch Dr Eric Berg explain why...
So yes, you have to eat vegetables, but a Keto diet proposes to eat no more than 20 gram of net carbs each day. To eat this little carbs you need to limit your carbs to non-starchy vegetables.
Also remember that some protein and fat sources also contains some carbs. So that should also be considered when calculating net carbs.