Nutritional deficiencies after bariatric surgery


Bariatric surgery is performed to treat obesity, where a surgeon removes or alters a part of your gut. This surgery is only performed as a last resort when the patient fails to lose weight with all other conventional measures (like diet, exercise, or medication). Bariatric surgery is extremely beneficial in maintaining weight with a supportive diet and exercise regime.  

One of the major concerns after weight loss surgery is malnutrition and undernourishment. 

Read on to know more…. 

Diet and nutrition after Bariatric surgery 

Diet plays an incredibly significant role before and after bariatric surgery. Because food is the only source of energy, you need to take care of your nutrition to build up your strength to cope with the surgery. Without proper nutrition, you can develop deficiencies that can be risky for your health.  

Here is the list of deficiencies you might develop if you don’t follow the prescribed diet and nutrition plan.  

1. Anemia:  According to the American Society of Hematology reports, people who have undergone bariatric procedures are at the highest risk for anemia, with 33% to 49% of patients developing anemia within 2 years of surgery.  

Anemia happens due to a lack of iron in the body, leading to a decrease in hemoglobin in your red blood cells.  

Causes: It can be due to: 

      • decreased capacity of your gut to absorb iron (due to gastric bypass),  
      • less gastric acid in your stomach (which doesn’t convert iron into its absorbable form), or  
      • less iron intake (due to diet restrictions).  


      • lack of energy  
      • Weakness 
      • Rapid heartbeat 
      • Hair loss and Frail nails 
      • Glossitis, stomatitis (inflammation of the tongue and corners of the mouth) 
      • Shortness of breath 


There are ways to restore the amount of iron in the body: 

      • Make changes in your diet to include iron-rich foods. 
      • Take supplements prescribed by your doctor to get the appropriate dose of iron. 
      • Take multivitamins along with iron every day.  
      • Add vitamin C to your supplements to help you to absorb more iron.  

2. Calcium and Vitamin D deficiency: A lack of calcium and vitamin D leads to weaker bones and an increased risk of fractures.  

Causes: It is caused by decreased calcium absorption (caused by bypassing the small intestine), which is the primary site of absorption. Calcium deficiency may also worsen by low calcium intake due to milk intolerance/exclusion in the post-bariatric diet. 

Vitamin D deficiency is due to the malabsorption of fats by the gut after bariatric surgery. 


  • Dull pain in bones 
  • Muscle weakness and pain 
  • Risk of fractures especially in ribs, spine, and legs. 
  • Joint pains and stiffness  
  • Fatigue and exhaustion                                                                                                


  • Take supplements of calcium (for adults between 1000mg and 1300mg) and vitamin D (at least 5000 IU) every day.  
  • Get regular sun exposure to stimulate vitamin D production in your body. 
  • Eat foods rich in calcium and vitamin D.

3. Vitamin B12 deficiency: Vitamin B12 deficiency is one of the most common vitamin deficiencies after weight loss procedures.  

Causes: Vitamin B12 deficiency can be caused by  

  • insufficient intrinsic factor secretion,  
  • low gastric acidity, and,  
  • bypassing the duodenum (it is the primary site of vitamin B12 absorption). 


  • Anemia 
  • Fatigue 
  • Numbness 
  • Memory problems and dementia 
  • Poor appetite 
  • Depression 
  • Glossitis (smooth, swollen tongue) 
  • Tiredness 
  • Problems with muscle coordination 
  • Pale skin and eyes 


  • You can take injections of vitamin B12 if your health provider recommends it. 
  • You need to take an oral dose of crystalline vitamin B12 to avoid deficiency.  
  • Make sure to eat plenty of whole grains, beans, and legumes in your diet. 

4. Protein Malnutrition: Protein Malnutrition happens due to poor digestion and absorption of proteins in the body.  


  • Vomiting after bariatric surgery 
  • Dumping syndrome 
  • Changes in enzyme functions (in gall bladder and pancreas) after bariatric surgery 
  • Less effective digestion of protein due to bariatric surgery 
  • Malabsorption of protein 
  • Decreased protein intake due to dietary restrictions 


  • Weight gain 
  • Behavioral changes- Irritability, decreased social responsiveness, anxiety, etc. 
  • Skin, hair, and nail problems 
  • Fatigue 
  • Swelling and edema (of legs and feet-most commonly) 
  • Hearing loss 


  • To avoid malnutrition and deficiency, take all recommended dietary proteins through food and supplements.  
  • Do regular training and exercise, especially aerobics, to preserve your lean and muscle mass.  
  • For severe degrees of protein malnutrition, patients should take amino acid supplements.  

5. Dehydration: Dehydration is one of the most common reasons that weight loss patients are admitted to the hospital after surgery.

Causes: Bariatric surgery changes the way your body tells you when you are hungry or thirsty, so the risk of dehydration is increased.  


  • Dry mouth and extreme thirst. 
  • Reduced urine production and urine that is darker in color; 
  • Dry skin; 
  • Chapped, dry lips 
  • Lightheadedness (due to a drop in blood pressure caused by dehydration)  


  • Keep track of your fluid intake 
  • Make sure to stay hydrated when exercising and working out 

Prevention of nutritional deficiencies after bariatric surgery 

The best way to prevent nutritional deficiencies is to:  

  • Eat a nutrient-dense, whole-food diet as directed by your doctor and nutritionist. 
  • Take dietary supplements recommended by your healthcare provider.  
  • Keep all your appointments with your bariatrics team, as recommended, and get regular tests to know if your body has enough nutrition that you need.  
  • Keep hydrated. 
  • Avoid Sugar, junk food, processed foods, and all sources of empty calories. 
  • Avoid drinking empty calories. 
  • Stop alcohol altogether or drink in moderation (if you absolutely must). 
  • Doing some physical training and/or light exercises also helps your body to absorb nutrition better. 

Bariatric surgery is the best treatment for obesity. But you need to take care of your diet and health before and after surgery to avoid complications that can even put your life at risk. To prevent these complications, follow all the guidelines given by your healthcare provider.  



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