Is there a difference between low carb and keto diets? The Dietitian Resource

Is There a Difference Between Low Carb and Keto Diets?

Have you ever wondered if there is a difference between low carb and keto diets? Perhaps these terms can be used interchangeably? In this article, you will learn more about the differences between low carb and keto diets.

From Your Friendly Neighborhood Registered Dietitian Nutritionist

As a healthcare worker and dietitian, I often hear patients say they are following “a low carb” or “keto diet.”  When digging a little further, I will ask how many grams of carb or fat they eat per day. Many clients cannot answer these questions because they simply do not know.

Dietitians do not recommend “dieting” because diets mean restricting food groups. Often these restricted foods groups are important for your health, or they include foods you love. When you are told you cannot have something, you simply want it more!

 If you choose to follow a low carb diet or a keto diet, dietitians want you to know everything about them. That way you can make the very best decision for your long-term health. Choosing your eating pattern is a very personal choice, and it should be made by having the best information available from credible sources.

To learn more about what to expect during an appointment with a registered dietitian nutritionist, please read this article.

A Brief History of Fasting and Keto Diets for Epilepsy

Starvation, or fasting, was practiced as early as 500 B.C. to treat epilepsy. Hippocrates, The Father of Modern Medicine, used fasting to treat epilepsy, fevers, and acute illness.

“Our food should be our medicine. Our medicine should be our food. But to eat when you are sick is to feed your sickness.” – Hippocrates.

Fasting is also mentioned in biblical text referring to when Jesus cured a boy of convulsive seizures (1).

In 1911 by Parisian physicians, Gulep and Marie, saw seizure severity was lessened in patients who were fasting. During the 1920s practitioners shifted from using fasting as an epilepsy treatment to using a high fat keto diet.

A timeline of starvation/fasting treatments to the keto diet for the treatment of epilepsy.

The Keto Diet and Epilepsy

The keto diet was well documented for the treatment of epilepsy in most textbooks between 1941 and 1980. Keto research declined after the anti-seizure medication, diphenylhydantoin, was discovered by Merritt and Putnam in 1938 (1).

Then, in the 1990’s, the keto diet came back into the spotlight after it was used to treat and radically improve the epilepsy of a 2-year-old boy named Charlie.

The Charlie Foundation now supports research and provides resources on the keto diet not only for epilepsy, but for many other medical conditions such as autism, early onset Alzheimer’s disease, brain tumors, diabetes (type 1 and type 2), Multiple Sclerosis, and more (2).

Defining the Difference between Low Carb and Keto Diets

A universal definition of “low carb” can be a challenge to find. When combing through various research articles, authors may title their diet as low carb (not keto) diet (LCD), low-carb keto diet (LCKD), very low-calorie keto diet (VLCKD), very low carb high fat (VLCHF) or even low carb high fat (LCHF).

The macronutrient ranges of these diets can vary as much as the names of the eating patterns used to describe them. So what makes a diet low carb, and what makes one keto?

Feinman et al. propose the following Carb Classification definitions in their 2015 review article based on a 2,000 calorie diet (3).  More resources were included in this table to support the proposed definitions.

Table 1: Proposed Carbohydrate Classifications

Very low-carb keto diet20 to 50 g/day or <10% of total calories (3) (4)
Low-carb diet<130 g/day or <26% of total calories (3) (4)
*50-150 g/day (10-30% of total calories) is suggested by other authors (5) (6)  
Moderate-carb diet>130 g/day or 26% to 45% of total calories (3) (4)
High-carb diet>225 g/day (based on a 2,000-calories diet) or >45% of total calories  (3)  

Low carb diets do not always lead to ketosis. If ketosis is desired, most individuals can reach a state of ketosis by restricting carb intake to <50 grams of carbs per day, or to a very low-carb keto diet (7) (8) (9) (4). 

Does Simply Reducing Carbs Create the Difference between Low Carb and Keto?

According to several authors, following a low carb (LC) diet does not have to mean high protein or high fat (4) (10) (11).  Instead, as carbs are reduced, “a spontaneous decrease in overall calorie consumption frequently results in little protein or fat added back in for the carb that is removed.” (10). 

Based on this idea, macronutrient distribution of calories would naturally shift as carbs are reduced making it appear as though protein and fat intake have increased when, in fact, they have not. For this reason, Noakes and Windt suggest that low carb high fat diets be called “low carb healthy fat” diets (4).

Comparing 300 grams of carb to 130 grams of carb

I wanted to see how only reducing carbs might look using a 2000 calorie diet consisting of 60% carb, 15.2% protein, and 25% fat is shown in the left column of the table below. The right column shows the reduction of carb intake to a moderate-carb diet range without changing the grams of protein or fat.

2000 calorie diet:1320 calorie diet (reducing carbs to 130 grams/day)
300 g carb (60% total calories) = 1200 calories
76.3 g protein (15.2% total calories) = 305 calories
55 g fat (25% total calories) = 495 calories  
130 g carb (39% total calories) = 520 calories
76.3 g protein (23% total calories) = 305 calories
55 g fat (38% total calories) = 495 calories  
– Reducing carbs from 300 g to 130 g reduced calorie intake by 680 calories.
– A 1320 calorie/day diet may not meet the resting energy needs of many individuals.

There is a 680 calorie reduction of carbs when reducing from a 300 g to a 130 g per day (moderate-carb diet).  This calorie restriction leads to a low calorie diet and is not realistic or sustainable for the average person if other macronutrients are not adjusted to increase calorie intake.

Comparing 225 grams of carb to 75 grams of carb

I tried using a different macronutrient distribution range (45% carb, 20% protein, and 35% fat) to see if this made a difference.  You can see the breakdown in the left column. The right column shows a carbohydrate reduction to a “low carb” level of 75 grams of carb per day.

2000 calorie diet:1399 calorie diet (reducing carbs to 75 grams/day)
225 g carb (45% total calories) = 900 calories
106.2 g protein (21% total calories) = 424.8 calories
75 g fat (35% total calories) = 675 calories  
75 g carb (21% total calories) = 300 calories
106.2 g protein (30% total calories) = 424.8 calories
75 g fat (48% total calories) = 675 calories  
– Reducing carbs from 225 g to 75 g reduced calorie intake by 601 calories.
– A 1399 calorie/day diet may not meet the resting energy needs of many individuals.

Again, there is a significant 601 calorie reduction in carbs that may not be realistic or sustainable long-term.  As previously said, restrictive diets do not work because they simply are too hard to maintain.  A 1399 calorie diet does not supply enough energy to sustain the resting energy needs of many people.

Do Keto Diets Prescribed for Epilepsy Differ from Mainstream Low Carb and Keto Diets?

The most researched keto diet is the Classic Keto (4:1) followed by the Modified Keto (3:1). These diets are prescribed to treat epilepsy.  

According to the Charlie Foundation, the classic and modified keto diet ratios can be calculated using the equation of (Fat/(Protein+Carb)).

  • For example, the classic keto diet is a ratio of four grams of fat to every one gram of protein and carb combined (12).
  • Protein is estimated to supply adequate protein intake for growth (1g/kg/day) (13).
  • Once protein requirements are calculated, carbs make up the difference in calories to meet the energy needs of the patient.

The Charlie Foundation presents a table (shown slightly modified below) of the Keto Diet Macronutrients; Percent of Total Calories (14). As a reminder, based on the definitions above, keto diets provide <10% total calories from carbs.

Macronutrient RatioFat % total calsProtein % total calsCarb % total cals
Classic Keto (4:1)90%6%4% (keto)
Modified Keto (3:1)87%10%3% (keto)
Modified Keto (2:1)82%12%6% (keto)
Modified Keto (1:1)70%15%15% (low carb)
Medium Chain Triglyceride (MCT) Oil (1.9:1)* 50%/21%19%10% (keto)
Low Glycemic Index Treatment (LGIT) (2:3)60%28%12% (low carb)
Modified Atkins Diet (MAD) (0.8:1)65%29-32%3-6% (keto)
* 50% MCT / 21% LCT: MCT stands for medium chain triglycerides, LCT stands for long chain triglycerides.

Low Carb and Keto Diet Definitions for Consideration

To summarize, low carb does not always lead to ketosis. To reach ketosis, most individuals would need to consume <50 grams of carb per day to be following a keto diet. Fat consumption is elevated when following a keto diet to meet energy requirements.

Based on information in current publications, the following definitions might be considered when discussing keto (very low-carb), low carb, moderate carb, and high carb eating patterns (based on a 2,000-calorie diet) (3) (9) (4) (11):

  • Very low-carb keto diet
    • 20 to 50 g/day or <10% of total calories
  • Low-carb diet
    • <130 g/day or <26% of total calories
    • Or 50-150 g/day
  • Moderate-carb diet
    • >130 g/day or 26% to 45% of total calories
  • High-carb diet
    • >225 g/day or >45% of total calories.
An image showing the considered definitions for keto, low carb, moderate carb, and high carb eating patterns (based on a 2,000 calorie diet).

Final Thoughts on the Difference Between Low Carb and Keto Diets

It is best to find an eating pattern that you can be tolerate and sustain long-term.  Per Zupec-Kania, a RDN specializing in ketogenic diets, when considering ketogenic diets start with:

  1. Limiting added sugar
  2. Focus on whole foods, and as a last resort
  3. Initiate ketogenic diet therapy. 

Often times limiting sugar and including whole foods can have a significant positive impact on your health and medical symptoms (15) (16).

To find a dietitian (nutrition expert) in your area, click here: Find a Nutrition Expert (eatright.org). When you collaborate with a dietitian, you will work to find an eating pattern that includes your favorite foods and opens opportunities to try new foods you may have never considered. Finding an eating pattern you can stick to long-term is the best way to support your health. It is a very personal journey.

For more information about The Dietitian Resource, visit our site or check out the blog.  To learn more about the Key Differences Between Dirty, Lazy, and the Clean Keto Diet, check out this post. Thanks for visiting!

References

1. History of the ketogenic diet. Wheless, James W. 2008, Epilepsia, pp. 49 (suppl. 8): 3-5.

2. Zupec-Kania, Beth. Modified Ketogenic Diet Therapy 1:1 and 2:1 Prescriptions: Metabolic Diet Therapy for Neurologic and Other Conditions [Brochure]. s.l. : Charlie Foundation for Ketogenic Therapies, 2018.

3. Dietary carbohydrate restriction as the first approach in diabetes management: critical review and evidence base. Feinman, RD, Pogozelski, WK and Astrup, A. 2015, Nutrition, pp. 31(1):1-13.

4. Evidence that supports the prescription of low-carbohydrate high-fat diets: a narrative review. Noakes, T.D. and Windt, J. 2016, Br J Sports Med, pp. 51: 133-139.

5. Hull, Michael, Leaf, Alex and Brown, Wyatt. Evidence-Based Keto – Your No-hype guide to the ketogenic diet. s.l. : Examine.com, 2019.

6. Low-carbohydrate nutrition and metabolism. Westman, E.C., et al. 2007, American Journal of Clinical Nutrition, pp. 86:276–84.

7. Implementing a low-carbohydrate, ketogenic diet to manage type 2 diabetes mellitus. Westman, E.C., et al. 2018, Expert Review of Endocrinology & Metabolism, pp. 13(5), 263-272.

8. Beyond weight loss: a review of the therapeutic uses of very-low-carbohydrate (ketogenic) diets. Paoli, A., et al. 2013, European Journal of Clinical Nutrition, pp. 67, 789-796.

9. Hull, M., Leaf, A., & Brown, W. Evidence-Based Keto – Your No-hype guide to the ketogenic diet. s.l. : Examine.com, 2019.

10. Low-Carbohydrate Diet Review:. Hite, A.H., Berkowitz, V.G. and Berkowitz, K. 2011, Nutrition in Clinical Practice, pp. 26 (3), 300-308.

11. Low-carbohydrate nutrition and metabolism. Westman, E.C., et al. 2007, American Journal of Clinical Nutrition, pp. 86:276-84.

12. Charlie Foundation for Ketogenic Therapies. Ketogenic Diet Therapies. [Online] July 8, 2022. https://charliefoundation.org/.

13. Mahan, Kathleen L. and Raymond, Janice L. Krause’s Food & The Nutrition Care Process (14th edition). St. Louis, MO : Elsevier, 2017.

14. Charlie Foundation for Ketogenic Therapies. Keto Therapies. [Online] July 8, 2022. https://charliefoundation.org/diet-plans/.

15. Zupec-Kania, Beth. KETOGENIC THERAPIES, LLC. Blog – Keto Intro for Professionals. [Online] April 25, 2020. https://www.bethzupeckania.com/blog-1/date/2019-08.

16. Zupec-Kania, Beth, Vanatta, Lisa and Johnson, Meredith. Ketogenic Diet Therapies for Neurological Disorders – Pocket Guide (2nd Edition). s.l. : Charlie Foundation for Ketogenic Therapies, 2019.

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More About Rochelle

Rochelle Inwood MS, RDN, ACSM EP-C

Hello there! I’m Rochelle Inwood, a Registered Dietitian Nutritionist (RDN) and Exercise Physiologist (ACSM EP-C). With over 14 years of experience, I have sharpened my expertise through diverse roles, including weight management program co-coordinator, patient/employee gym supervisor, outpatient dietitian, program manager, dietetic internship preceptor, and more. I am passionate about learning, creating, teaching, and supporting personal growth and development.