Kidney Health After Metabolic and Bariatric Surgery

Kidney Health After Metabolic and Bariatric Surgery - Bariatric Fusion

Guest Blog By: Dr. Lillian Craggs-Dino, DHA, RDN, LDN

The prevalence of severe obesity is a continuing epidemic that can adversely affect cardiovascular health and renal function, increasing the risk of obesity-related comorbidities. (1,2)

Thankfully, metabolic and bariatric surgery (MBS), such as roux-en-y gastric bypass surgery (RYGB), is an effective weight loss tool to support improved quality of life and to assist patients in reaching their health goals. However, surgery is not without risk factors, including nutritional risk.

MBS requires dietary and lifestyle changes, including consuming adequate proteins, meeting fluid goals, and taking lifelong vitamin and mineral supplements.

This article discusses the beneficial effects of decreased body weight and healthy body mass index (BMI) following MBS. We also share five tips for supporting healthy kidney function.

The Importance of Healthy Kidney Function

Every organ of the human body plays a role in our health, and the kidneys are no exception.

The kidneys support healthy urinary function by filtering and removing metabolic byproducts and toxins from your body. These two bean-shaped organs support a healthy balance of water and electrolytes in your blood, including sodium, calcium, phosphorus, and potassium.

Proper kidney function plays a role in activating functional vitamin D, secreting hormones necessary to produce red blood cells, and supporting healthy blood pressure. If the kidneys are injured or damaged, comorbidities such as osteoporosis, anemia, and high blood pressure can occur.

How to Test Kidney Function

Blood and urine tests are the best way to measure kidney function. Since the kidneys play a crucial role in the excretion of waste and excess fluid from the blood, lab work will show how efficiently your kidneys are removing that waste.

If your healthcare provider has concerns about your kidney function, there will be a focus on lab results, such as serum creatinine, glomerular filtration rate (GFR) or estimated glomerular filtration rate (eGFR), albumin test for albuminuria, and blood urea nitrogen (BUN).

Although these terms can get confusing, it is vital to have a baseline understanding of the different tests that may be ordered to ensure proper kidney function. If the results of any kidney-specific test come back abnormal, you may be referred to nephrology for a follow-up.

Kidney Function and Metabolic and Bariatric Surgery (MBS)

How to Test Kidney Function

So, what does kidney function have to do with MBS?

Weight loss induced by MBS supports positive outcomes for the long-term risk of decreased kidney function and end-stage renal disease (ESRD). (3)

However, healthy lifestyle changes are required for a successful weight loss journey. For example, if persistent dehydration pursues after surgery due to inadequate fluid intake, observational studies show that MBS can put patients at a higher risk of oxalate kidney stones and even acute kidney injury. (4,5,6)

Kidney Health and Dehydration

Dehydration is one of the most common but preventable incidences that can cause readmission to the hospital post-op metabolic and bariatric surgery. (7)

Adjusting to new dietary habits after surgery can be difficult. In the early phase after surgery, drinking adequate fluids, especially the recommended 64-72 ounces, can be challenging.

As you learn the boundaries of your weight loss tool, you may feel an overwhelming sense of fullness or experience taste and texture aversions, even to fluids. However, fluid intake is paramount for supporting healthy kidney function.

Symptoms of Dehydration

Signs and symptoms of dehydration may include the following:

  • Little or no urination
  • Dry throat, lips, and eyes
  • Feeling sleepy or extremely fatigued
  • Extreme thirst
  • Headache
  • Confusion
  • Dizzy or lightheaded

    Not only can dehydration present in the typical symptoms above, but it can affect how protein is absorbed, causing temporary proteinuria or protein in your urine.

    As you participate in a healthy lifestyle with the assistance of MBS, a bariatric diet, and exercise, your kidney health should also be a priority.

    5 Tips for Healthy Kidney Function

    5 Tips for Healthy Kidney Function

    Here are five nutritional tips to support renal function and kidney health after metabolic and bariatric surgery.

    DASH Diet

    The kidneys are sensitive to damage when high blood pressure is present. You can support healthy blood pressure by incorporating foods that follow the DASH diet into your bariatric routine.

    The DASH (Dietary Approaches to Stop Hypertension) diet is a dietary approach that can be effective in reducing hypertension (high blood pressure). It includes foods rich in potassium, calcium, and magnesium, such as fresh fruits, vegetables, legumes, and lean proteins.

    Sodium Intake

    High sodium (salt) intake can cause the kidneys to have reduced function. Not only does the DASH diet support healthy blood pressure, but it also limits foods high in sodium (salt).

    Normal sodium intake is no more than 1,500 mg daily. That would mean putting down the saltshaker since one teaspoon of salt contains 2,300 mg of sodium!

    Adequate Fluids

    After metabolic and bariatric surgery, the goal is to drink 64-72 ounces of sugar-free, carbonation-free, alcohol-free fluids daily.

    If you have difficulty remembering your fluids, carry a water bottle, keep fluids in easy-to-reach places, and set reminders on an app. Make sure you drink slowly and avoid straws to limit gas.

    Limit Caffeine

    Excessive amounts of caffeine can be dehydrating and can also be high in sugar and calories. Limit caffeine to 400 mg daily, which may equate to 1 serving of coffee daily.

    Calcium Supplementation*

    In the presence of chronic kidney disease (CKD), kidney failure, or even acute kidney injury, there may be an imbalance in your calcium and phosphorus levels. (8)

    Your healthcare provider may recommend calcium citrate as a supplement to support kidney health. Always follow your healthcare provider's considerations for supplement dosage.*


    The prevalence of global obesity can, unfortunately, contribute to several obesity-related conditions, including type 2 diabetes, hypertension (high blood pressure), cardiovascular disease, and kidney disease.

    Metabolic and bariatric surgery (MBS) can be a life-changing option to support a healthier quality of life. Lifelong supplementation, dietary, and lifestyle changes must be maintained throughout life to reap the benefits of surgery.

    If you experience setbacks after surgery, utilize the resources around you, including bariatric support groups and the help of your bariatric healthcare team.


    1. Nutrients. 2021; 13(12):4482 [PMID: 34960033]
    2. Circulation. 2021; 143(12):e984-e1010 [PMID: 33882682]
    3. Kidney Int Rep. 2017; 2(2):261-270 [PMID: 28439568]
    4. Kidney360. 2020; 1(12):1456-1461 [PMID: 34085046]
    5. Kidney Int. 2015; 87(4):839-45 [PMID: 25354237]
    6. Obes Surg. 2013; 23(1):64-70 [PMID: 22972198]
    7. Surg Obes Relat Dis. 2019; 15(12):2066-2074 [PMID: 31601534]
    8. Curr Osteoporos Rep. 2017; 15(3):214-221 [PMID: 28474258]

    *These statements have not been evaluated by the Food & Drug Administration (FDA). These products are not intended to diagnose, treat, cure, or prevent any disease.

    This blog is for information and education purposes only. This information is not intended to substitute professional medical advice, diagnosis, or treatment. Please consult with your bariatric surgeon or another qualified healthcare provider with any questions in regards to a medical condition. A qualified healthcare professional can best assist you in deciding whether a dietary supplement is suitable based on your individual needs.

    Dr. Lillian Craggs-Dino is a retained consultant for Bariatric Fusion.

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    Dr. Lillian Craggs-Dino, DHA, RDN, LDN, CLT

    Dr. Lillian Craggs-Dino is a nationally and internationally known Registered and Licensed Dietitian Nutritionist with more than 20 years professional experience in bariatric nutrition. She holds a Doctorate Degree in Health Administration from the University of Phoenix and a Master of Science degree in Dietetics and Nutrition from Florida International University. She is the Advanced Practitioner Level II Bariatric Dietitian and Support Group Coordinator for Cleveland Clinic Florida where she has had much success assisting patients with their nutritional and weight loss goals.

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