Keto | Popular Diets after Bariatric Surgery

Steph Wagner MS, RDN

May 3, 2022

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Keto after Bariatric Surgery

Popular Diets after Bariatric Surgery Blog Series

Read the recap blog for the Popular Diets after Bariatric Surgery Series here including a full comparison chart!

Tips when researching about a diet

When it comes to understanding a diet, I like to know the whole story. When did it start? Who is behind it?

This little practice also helps me to find any red flags. If you cannot find any information about the founder(s), the origins, the methodology or it even seems they are hiding those details, I would avoid the diet or product.


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The backstory on the keto diet

The keto diet is currently a big name mainstream diet.

The backstory is that keto is short for ketosis.

When your body uses fat for energy, ketones are created as a byproduct. That process is called ketosis. A ketogenic diet, therefore, is any diet that puts the body into ketosis.

“The clinical ketogenic diet” was first used in the 1920s as a treatment to epilepsy.

When medications fail to achieve the management of seizures, the diet continues to be a treatment option. In these situations, the patients are admitted to the hospital and closely followed by a ketogenic team.

In the 1990s, a ketogenic diet started to gain popularity for weight loss.

There are several mainstream diets that would fall into this category of ‘ketogenic’ including Atkins, South Beach or even Paleo at times. These are low carbohydrate eating plans that put the focus more on limited carbohydrate than limiting calories specifically. As a result, the body uses fat for fuel and is in a state of ketosis.

🍓A Quick Note on Ketosis

You may have personal experience with low carb diets that encourage ketosis. You may have even used ketone strips to see if you were in ketosis.

These ketone strips are intended for diabetic patients. Diabetic ketoacidosis is very dangerous and is when someone with the disease of diabetes doesn’t have enough insulin and blood sugars are too high for too long.

Those with diabetes need to continue to manage blood sugars and work with their health care team if they need more support in staying controlled.



What does the ‘keto diet’ of today advise?

The keto diet aims to mimic the effect of fasting. This is why it is often paired with intermittent fasting (which we will cover next week).

The mainstream “keto” in our current culture can take on a lot of different forms from the classic keto plan. Often the plans will use macros to define itself. We talked a lot about macros last week. 

First, let’s cover the classic or ‘clinical’ keto diet and then we’ll talk about the ways it can branch off.

🍓 Clinical/Classic/Standard “Keto” Diet

The clinical eating plan for treating seizures in epilepsy patients is as high as 75-90% of calories from fat.

Carbohydrates are limited to 20-50 grams per day. To do so, this would be carbs primarily just from non-starchy vegetables.

Protein is kept high enough to maintain lean body mass, but low enough to be in ketosis.

Common foods on a keto eating plan would include avocado, high fat cheese, cream, butter, oils, nuts, seeds, meat, poultry and fatty fish.

Let’s keep talking about other variations of keto, but let me say here that 75-90% fat is not recommended for bariatric surgery patients. That amount of fat would be very hard on the digestive system and cause diarrhea or possibly dumping syndrome.

🍓 Variations of the Keto diet

There are many variations of the mainstream “keto” diet. Here’s a quick list to showcase them:

Targeted Keto (for athletes looking to improve performance)

High Protein Keto (for body builders)

Cyclical Keto Diet (for help sticking to the diet)

Lazy Keto Diet (on track carbs, not calories fat or protein)

Mediterranean Keto (focus on heart healthy fat sources)

Keto 2.0 (50% fat, 30% protein, 20% carb)

Dirty Keto (standard plan but more processed/packed meals for those who lack time)

Clean Keto (organic and healthier versions of foods)


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Is there research about the keto diet and bariatric surgery?

The short answer is not much.

One research study did a retrospective analysis of medical charts of eleven post-op gastric bypass patients who did not lose more than 50% of their excess body weight. (When it comes to research, losing more than 50% of excess body weight after weight-loss surgery deems it successful).

The patients followed a very low-calorie ketogenic diet. Note, this doesn’t mean they followed the mainstream “keto” diet. Instead it means the diet was low calorie, low carb and low fat (hard to stay low calorie with high fat foods).

The results did show significant weight loss in these patients. The limitations of course are that it was just eleven patients and we don’t know how long they maintained the eating plan. They did note there were no serious adverse events for the patients following the plan.



Is keto after bariatric surgery okay to try?

As previously mentioned, the high fat content is not idea for post-ops. It can be hard on the GI system plus is high calorie containing. High fat meats, cheeses and nuts can add up very quickly.

Last week we talked about macros and bariatric surgery with research supporting a post-op eating plan of 50% protein and 30% or lower carbohydrate. That would make it a ketogenic eating plan. It is a more protein focused, lower fat version compared to the mainstream keto.

My other comments if this questions is on your mind:

Anytime someone asks me about a diet plan, I usually answer their question with a question. Where did you hear about it? What do you know about it? What are you hoping it will do for you?

These questions help us get to the root of what they are looking for. Is it possible to mold the eating plan to better fit their post-op needs and they lifestyle and goals. (Yet another plug for working with a bariatric dietitian!)

More often than not, the key is getting back to the basics like staying hydrated, meal planning and exercising.


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In summary about the keto diet and bariatric surgery

To conclude, there is not a vast amount of research. The amount of fat in the classic keto diet will typically need to be adjusted for a bariatric surgery patient.

Following a bariatric eating plan (like the 2:1 Protein Method described on this blog) will still be a ketogenic style diet utilizing fat for fuel instead of carbohydrate.

One other thing to mention is to be mindful of the word KETO on recipes or food products. Anytime a diet has a lot of attention, foods will be marketed heavily with that name.

When a product or recipe has the word keto, you can bet it will be very high in fat which will therefore be very high in calories. By the way, Atkins products now add the word KETO to packaging but the products are not different.



Stay tuned! Intermittent Fasting will be up next.

We will continue our series next week on Intermittent Fasting! Keto is often paired with IF and we’ll talk about why.

In case you missed, below are links to previous blogs in the series:

The Bariatric Diet

The Bariatric Plate Method (and what I used instead)

The Scoop on Macros

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