The Ketogenic Ratio Explained

If your child’s physician has recommended a ketogenic diet for epilepsy management, you likely have many questions, which may have led you to this post. As you collect information online and educate yourself on the topic, you may come across the term “ketogenic ratio” and wonder what it means. I’ll try to clear things up in today’s post.

Infographic by Lurie Childrens Hospital

The classical ketogenic diet for epilepsy is designed according to a ratio. This ratio, often referred to as the “ketogenic ratio”, represents the amount of fat in the diet, in comparison to the amount of protein plus carbohydrate. If you are a visual person like me, this infographic to the right, which was created by the awesome keto team at Lurie’s Children’s Hospital, will help explain the concept better.

If the last paragraph didn’t trigger long-forgotten memories of middle-school math class, the remaining paragraphs surely will. Don’t worry if math is not your thing- the fundamentals will come back to you quickly. Many keto parents will tell you that managing their child’s ketogenic diet revealed math and cooking skills they never knew they had! Also, keep in mind that the ketogenic dietitian who you work with will very carefully design and calculate your child’s diet, helping you to manage it at every step along the way, so you are by no means on your own.

The most commonly used ketogenic ratios are 4:1 and 3:1. A 4:1 ketogenic ratio describes a ketogenic diet that is made of 4 grams of fat for every 1 gram of protein plus carbohydrate. In other words, for every 5 grams of food consumed, there are 4 grams of fat and 1 gram of protein and/or carbohydrate. Therefore, a 4:1 ketogenic diet contains 80% fat (4÷5=80%) and 20% protein plus carbohydrate (1÷5=20%). Likewise, a 3:1 ketogenic diet contains 75% fat (3÷4=75%) and 25% protein plus carbohydrate (1÷4=25%).

Notice that the ketogenic ratio compares the amount of fat, protein, and carbohydrates in grams, a measure of weight. This is because the diet is calculated in grams, since foods are measured by weight using a gram scale.

If you compared fat, protein and carbohydrates according to the number of calories provided from each (rather than the number of grams of each), the ratio would be a little different because fat provides more calories per gram than protein and carbohydrates do. Each gram of fat provides the body with 9 calories, while each gram of protein or carbohydrate provides the body with 4 calories.

For example, let’s say that you need to consume 360 calories. To provide 360 calories from protein and/or carbohydrate (which both provide 4 calories per gram), you would need to eat 90 grams of protein and/or carbohydrate (360÷4=90). However, to get the same amount of calories from fat, you would need to eat just 40 grams of fat (360÷9=40). Fat provides the same number of calories with much less mass because it is more calorically dense than protein and carbohydrates.  For this reason, ketogenic meals tend to look smaller than standard meals, even when they provide the exact same amount of calories.

If a child is on a 4:1 ketogenic ratio, 90% of the calories in their diet comes from fat. Did I lose you there? This part confused me
at first because I thought “how can it be both 80% fat and 90% fat?”. The answer is that it is 80% fat if you are measuring by weight and 90% fat if you are measuring by calories.  Remember that a 4:1 ketogenic ratio represents 4 grams of fat for every 1 gram of carbohydrate plus protein. Four grams of fat (which provides 9 calories per gram) provides a total of 36 calories (4 x 9 = 36). One gram of protein or carbohydrate (which provides 4 calories per gram) provides a total of 4 calories (1 x 4 = 4). The ratio of calories from fat to calories from protein plus carbohydrate is 36:4. This means that for every 40 calories consumed, 36 come from fat and 4 come from protein and/or carbohydrate. Thus, 90% of the calories comes from fat (36÷40=90%), and 10% comes from protein and carbohydrate (4÷40=10%). On a 3:1 ketogenic diet, about 87% of the calories comes from fat, and 13% comes from protein plus carbohydrate. For comparison’s sake, a typical American diet contains about 35% of calories from fat and about 65% from protein and carbohydrate.

3-1typical

I hope that this post helped to explain the ketogenic ratio and the basic design of the ketogenic diet, but if you have any questions or need anything clarified, please comment and we’ll do our best to help!

-Mallory