Intermittent Fasting | Popular Diets after Bariatric Surgery

Steph Wagner

May 10, 2022

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Intermittent Fasting after Bariatric Surgery

Popular Diets after Bariatric Surgery Blog Series



The backstory on intermittent fasting

Intermittent fasting is a mainstream eating philosophy in our current culture although fasting has been done for centuries for religious purposes. Using periods of fasting for weight reduction has roots in the 1940s. Physicians recommended short periods of starvation as a safe and effective method of weight reduction.

In 2012 intermittent fasting really picked up attention after a television documentary Eat, Fast and Live Longer. Since then many celebrities have endorsed it and mainstream attention exploded.

Medical professionals including doctors and dietitians recommend various forms of time restricted feeding for certain patients.



What does intermittent fasting advise?

Intermittent fasting is not about what to eat but about when to eat and when not to eat.

The primarily methodology behind periods of feeding and fasting is related to insulin. After a meal insulin levels spike and then slowly returns to baseline.

When insulin levels are high, it’s more difficult to burn fat. If food is eaten before insulin returns to baseline, insulin will spike again, keeping the body in a higher insulin state.

Periods of fasting  would allow for the dieter to stay in a low-insulin state longer, making it easier to burn fat when eating at a calorie deficit.

Focusing on quality foods would still be advised by those supporting a IF plan, but the approach is less about a calorie counting plan and more about fueling up during those windows.

🍓 Different Schedules of Intermittent Fasting

Just like Keto has several variations, so does intermittent fasting schedules.

A very common schedule is 16 hours of a fasting state and 8 hours of a feeding window.  Some will advise to keep the feeding state to earlier in the day (such as 7am to 3pm or even 10am to 6pm) but not before bed.

You will also hear about schedules that are larger windows of fasting such as 20 hours with just 4 hours of feeding. Still other schedules will have days of fasting and days of feeding.

But the question we are here for: Should bariatric surgery patients use intermittent periods of fasting?



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Is there research about intermittent fasting and bariatric surgery?

While there is research on intermittent periods of fasting and the benefits of cardiovascular disease or weight loss, there is not specially research for bariatric surgery patients.

Also note, the research supporting intermittent fasting is more commonly on animals.

When it comes to research it is more common to find studies comparing different methods of treating obesity.  Intermittent fasting might be a method compared to bariatric surgery but not in conjunction with.

What research can tell us is that bariatric surgery continues to be the most effective treatment of obesity for weight loss and diabetes remission compared to non-surgical treatments.



Is intermittent fasting after bariatric surgery okay to try?

Well, maybe.

The majority of bariatric programs and dietitians will be quite cautious and hesitant to recommend periods of fasting to a post-op bariatric surgery patient. The primary reason for the caution is to meet nutrition needs.

Since the surgical pouch limits food intake, there are already limits to getting enough quality protein, fiber and nutrition in the body. If the limitation of time is put on top of that, can the patient meet all their nutrition needs?

Bariatric patients have the advantage of the surgery tool which does help insulin levels and metabolic function. When their diet is clean and focused on lean proteins and vegetables, it may not be necessary to have periods of fasting because the benefits already exist. Especially if the patient is filling up at meal times and focusing on hydrating fluids in between meals compared to a grazing pattern through the day or high carbohydrate meals that initiates a bigger insulin response.

There may be times, patients or professional that will utilize specific eating schedules and put time frames on when to eat and when to avoid. This is best done with the clinical judgment and guidance of a professional to make sure your nutrition needs are being met and that it is a good choice. Is your hunger controlled? Are you protein needs being met? Is this a sustainable plan? These are the questions a dietitian will help you work through.


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In summary about the keto diet and bariatric surgery

To conclude, there is not research specific to intermittent fasting after bariatric surgery. The primary concern and reason many providers would hesitate to use IF after surgery relates to meeting adequate nutrition needs when food intake is already restricted.

Bariatric surgery continues to be the most effective treatment of obesity. Getting back to basics and following a diet focused on quality protein, non-starchy vegetables, staying hydrated, active and sleeping well will allow you to get the most out of your surgery.

Use post-op eating behaviors like small bites and pausing in between bites to allow you to fill up at your protein based meals instead of stopping on a small portion, being hungry sooner and grazing through the dya.

And as a quick reminder, you are considered a success story when you have lost half the weight you were overweight. If someone had 100 pounds to lose and they lost 50 pounds, they are a success story!

The main goal (in my opinion) after bariatric surgery is to get out of the obese category. Since it is a treatment in the disease of obesity, we want to beat obesity and build habits that will help you continue to manage the disease and stay out of the obese category.



Stay tuned! Noom will be up next.

We will continue our series next week on the popular app Noom!

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

Keto after Bariatric Surgery

Become a Member





Diet review: Intermittent fasting for weight loss. The Nutrition Source. (2019, May 22). Retrieved May 10, 2022, from

Rynders, C. A., Thomas, E. A., Zaman, A., Pan, Z., Catenacci, V. A., & Melanson, E. L. (2019, October 14). Effectiveness of intermittent fasting and time-restricted feeding compared to continuous energy restriction for weight loss. Nutrients. Retrieved May 10, 2022, from

Staff, H. H. P. (2021, February 28). Intermittent fasting: The positive news continues. Harvard Health. Retrieved May 10, 2022, from


Intermittent Fasting: Is It Safe After Bariatric Surgery? (n.d.). Retrieved May 10, 2022, from,surgically%20restricted%2C%E2%80%9D%20Parrott%20said


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