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Home arrow Health arrow Bariatric surgery patients: a nutritional guide

Physical Activity

Epidemiological studies suggest that physical inactivity is a major cause of obesity. There is little agreement that a sedentary lifestyle is the cause of obesity or that physical activity prevents weight gain through improved metabolic management. The evidence to support a more active lifestyle as the key to weight loss and improved health is weak [4] so a modest approach to increased walking, biking, or swimming could help improve weight loss potential with a 30-minute per day recommendation. A combination of s urgery-induced diet restrictions and modest daily exercise may be the key to future success but more research is needed on this.

Drug-Nutrient Interactions

Clinicians can fail to recognize the importance of drug-nutrient interactions when assessing the nutrition status of bariatric surgery patients but health-care professionals need to be aware of the malnutrition factors that drugs may cause. Medications may modify nutrient absorption, metabolism, and excretion of nutrients in the following ways:

  • • Alter nutrient absorption by changing the acidity of the digestive tract (e.g., antacids interfere with iron and folate absorption)
  • • Damage the small intestine mucosal cells
  • • Bind nutrients (e.g., bile acid binders bind to fat-soluble vitamins)
  • • Stimulate gastric acid secretion (e.g., antifungal ketoconazole is absorbed better with meals due to acid secretion)
  • • Alter gastric emptying (e.g., when drugs are taken with food)
  • • Compete with food for absorption in the intestines, especially amino acids
  • • Use similar enzyme systems for metabolism (e.g., liver enzymes increase metabolism of folate, vitamin D, vitamin K)
  • • Alter reabsorption in kidneys (e.g., diuretics increase excretion of sodium and potassium) [5]

Drugs and nutrients interact metabolically because they use the same enzyme systems in the small intestines and liver. Drugs may enhance or inhibit the activity of enzymes needed for normal nutrient metabolism or dietary components may enhance or inhibit enzymes that break down drugs. Select examples include [5] the following:

  • • Methotrexate—used for inflammation, resembles folate, and competes with the enzyme that converts folate into its active form
  • • Corticosteroids—used for inflammation and immunosuppression can cause weight gain, muscle wasting, bone loss, hyperglycemia
  • • Phenobarbital and phenytoin—used as anticonvulsant interferes with the metabolism of vitamins D and K
  • • Warfarin—used as anticoagulant interacts with vitamin K to prevent blood-clotting factors

• Monoamine oxidase (MAO) inhibitors—medications used to treat depression block an enzyme that inactivates tyramine, epinephrine, and norepinephine

The enzyme system responsible for the metabolism of most nutrients and drugs is the cytochrome P450 (CYP) enzyme family located in the endoplasmic reticulum of the hepatocytes and enterocytes [6]. Vitamins and dietary factors are known to modify CYP activity. Dietary factors that increase CYP activity are

  • • Calorie restriction
  • • Charcoal cooked foods
  • • Garlic oil, fish oil
  • • Protein supplementation
  • • Thiamine deficiency
  • • Vitamin E supplementation

Dietary factors that reduce CYP activity are

  • • Iron deficiency
  • • Protein deficiency
  • • Starvation
  • • Vitamin A deficiency
  • • Vitamin C deficiency

Failure to identify and manage drug-nutrient interactions can cause serious consequences like compromised immune function, treatment failure, or morbidity [6].

Drugs that are recommended to be taken with food to maximize absorption are [7,8]

Albendazole Ketoconazole

Amiodarone Lithium

Atazanavir Lopinavir

Atovaquone Lovastatin

Cefuroxime Mefloquine

Erythromycin Nelfinavir

Ganciclovir Rifapentine

Griseofulvin Ritonavir

Hydralazine Saquinavir

Drugs that should not be taken with food to allow optimal absorption are [7,9,10]

Ampicillin Isoniazid

Captopril Norfloxacin

Ciprofloxacin Oflaxacin

Didanosine Rifampin

Dicloxacillin Voriconazole

Doxycycline Zafirlukast


The reason for not consuming drugs with food include: acid liability, chelation, or binding with food content.

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