Dietary Recommendations After Gastric Bypass Surgery
When obesity gets out of hand, unresponsive to dietary, lifestyle and medical interventions, drastic measures are needed to cut down calorie intake. Morbid obesity with a BMI (body mass index, a measure of malnutrition) above 40 kg/m2 is an indication for surgical procedures such as gastric bypass surgery. Gastric bypass is now a well-trodden path to lower BMI's and achieve healthier lives in 18 months or so. First used in the 1950's, only the last two decades have seen safe and successful gastric bypass surgery with any consistency. Half a century of meticulous observations and patient follow-up has led to the formulation of strict guidelines to ensure desired results.
Gastric bypass is a series of steps initiated starting with the decision to undergo the procedure. Identifying existing nutritional deficiencies is the first step towards surgery. Vitamin and mineral deficiency often occur in obesity, and need to be addressed before the procedure. The surgery itself has two goals; to reduce the volume of the stomach and shorten the food transit time in the intestine. After surgery the stomach cannot receive large meals or participate in digestion. This by itself limits food intake. Food also bypasses a large part of the intestine and has little time to interact with liver and pancreatic enzymes. As a result, nutrition absorbed from diet drops drastically. In most types of gastric bypass surgeries done today only 50 cm of the intestine is allowed to function in normal fashion. Compare this to food absorption taking over 7 feet of small and large intestine before surgery.
With such a radical reduction in the capacity to assimilate food, the postoperative period can be rather tricky. Only clear fluids are advised for the first two days while waiting for gut to recover. The gut is then re-trained for about two months before it can go back to a normal diet. During the recovery period the limitations imposed by the gastric bypass procedure should be kept in mind. After surgery the stomach has become much smaller and can only hold approximately eight ounces at a time. The stomach has also lost its ability to pulverize food to initiate digestion. Consequently the appropriate diet for postoperative recovery would be a liquid to soft solid diet that can be taken six to eight times a day in small quantities. Nutrient fluids are preferable since they can provide hydration and energy at the same time. Non-nutrient fluids are best avoided or at least restricted to in-between meals.
The type of nutrient chosen also deserves due consideration. The chosen macronutrient should not affect the stomach emptying time while providing enough energy to recover from the surgery. In this regard carbohydrates and fats are at either end of a spectrum and neither is suitable. Carbohydrates pass through very quickly and produce very uncomfortable symptoms like vomiting, bloating, diarrhea and sweating. Fat slows the gut considerably, and it is oftentimes ruled out because of its direct link to obesity. Research suggests that the macronutrients of choice after gastric bypass surgery are proteins. Proteins do not change gastric transit time significantly. A high-protein diet can also provide enough amino acids for repair and growth after a major surgical procedure like gastric bypass.
Apart from these advantages, a high-protein diet has a special role in the treatment of obesity. Gastric bypass restricts excessive calorie intake to prevent weight gain. However, accumulated adipose tissue also needs to be expended to achieve the desired weight loss. The basal metabolic rate (energy expenditure) should be increased simultaneously to burn stored fat and reduce BMI. This can be achieved by a high-protein diet since proteins in diet increase the basal metabolic rate by stimulating protein synthesis. Observations made during the postoperative period also confirm this proposition. Unless a high-protein diet is provided, weight loss often ceases despite controlled consumption.
Currently, a protein intake of up to 90 grams per day is recommended in the post-operative period. Given the trauma and the limitations the gut is subjected to during the procedure, such a high protein intake can be difficult to maintain. The gut is hardly ready and often fails to assimilate proteins and energy from traditional foods and diets. Therefore, a sugar-free fluid protein concentrate with a high bioavailability, adequate essential amino acids, vitamins and minerals is the most appropriate diet in the post-operative period. Digestion is further facilitated if the protein concentrate is already pre-digested, or hydrolyzed. Such a nutrient fluid can simultaneously supply concentrated energy and hydration even when taken in small quantities.
After recovery and return to a normal diet divided over 3 to 4 meals per day, a high-protein concentrate is still a relevant supplement between or during meals. The protein supplement continues to provide thermogenic action necessary to lose weight essential to sustain weight loss. It also compensates for any amino acid deficiency in the diet and maintains nutrition on bad days not uncommon in the months and years after a major surgery.
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