Skip to content

You are reading 1 of 2 free-access articles allowed for 30 days

Bariatric surgery and obesity

According to the World Health Organisation (WHO), the worldwide prevalence of obesity nearly doubled from 1980 to 2008. In Europe, the latest estimates reveal that between 10-to-30 per cent of adults are obese. In Ireland, the number of adult males and females over 20 years of age who are obese is estimated to be 22.9 per cent and 22.5 per cent respectively, which is above the European average.

Bariatric surgery is growing in popularity as the most effective treatment for obese individuals, especially those with comorbidities. As the number of procedures increases, physicians in primary care to acute hospital settings may be caring for individuals who have had the surgery. This article will give an overview of the procedures and the nutritional implications associated with each procedure.

The recent publication of the second UK and Ireland Bariatric Surgery Registry in 2014 indicated that 161 surgeons from 137 hospitals recorded 18,283 operations in the years 2011-2013. Of the 18,283 procedures, 4,705 were gastric band, 3,797 were sleeve gastrectomy and 9,526 were gastric bypass. This does not include the increasing number of patients who have had procedures (particularly gastric bands) carried out beyond the UK and Ireland.

The average BMI was 48.8kg/m2 and 53.9 per cent of men and 41.4 per cent of women had a high level of co-existing disease (four or more obesity-related diseases). The average weight loss three years after primary bariatric procedures is 59.6 per cent of the patient’s excess body weight.

In the Bon Secours Hospital, Cork, the bariatric service was established in 2008 under Mr Colm O’Boyle, Consultant Bariatric Surgeon, and the multidisciplinary team also consists of a Consultant Respiratory Physician; Consultant Endocrinologist; Consultant Cardiologist; Clinical Psychologist; Senior Dietitian; Gastroenterology Specialist Nurse; Chartered Physiotherapist; and Patient Service Co-ordinator. The team tends to adopt a biopsychosocial approach to the management of the bariatric patient, acknowledging the complexities of the causes of obesity and ensuring that the patient will achieve the best possible outcome and quality of life from their surgery.

Since the inception of the service, over 360 procedures have been performed, mainly by either laparoscopic sleeve gastrectomy or by laparoscopic Roux-en-Y gastric bypass. There is also an increasing number of patients opting for revisional surgery to remove slipped gastric bands.

The procedures

Please see for videos and more information on the procedures outlined below.

The laparoscopic adjustable gastric banding (LAGB)

In this procedure, a restrictive band is placed around the top of the stomach, creating a small pouch and restricting passage of food into the remainder of the stomach. A saline solution is added to tighten the band and this can be adjusted to allow more or less food to pass through, depending on intake and weight loss goals. This procedure is considered restrictive, reducing the amount of food consumed.

The laparoscopic sleeve gastrectomy (SG)

This procedure involves creating a stomach ‘sleeve’, with a capacity of around 120 to 200mls, with a stapling device and removing up to 80 per cent of the stomach. The pyloric sphincter and intestines remain, so the food pathway is not altered. This procedure is considered restrictive and metabolic, as there is some degree of gut hormone change, which decreases hunger and increases satiety.

Micronutrient deficiencies are less common with this procedure because the whole of the small bowel is still available for digestion and absorption. However, compliance with balanced diet and life-long supplementation may increase the risk.

The laparoscopic Roux-en-Y gastric bypass (RYGB)

This procedure involves creating a small pouch of about 30mls (egg-cup size) at the top of the stomach. A Roux-en-Y limb is created and attached to the pouch, bypassing the stomach, the duodenum and the first part of the jejunum, allowing for food to directly enter the small intestine.

The bypassed stomach remains, allowing for secreted digestive enzymes to travel through the pancreatic limb and empty into the common channel. This procedure is considered restrictive, with some malabsorption of nutrients, and is thought to have a more profound effect on gut hormones that can reduce hunger, increase satiety and allow for most patients to come off their diabetic medications immediately after the operation. This procedure impacts on the absorption of iron, vitamin B12, calcium and vitamin D in particular.

Both the SG and the RYGB have an effect on the gut hormones GLP-1, PYY and ghrelin.

GLP-1 acts synergistically with PYY to induce satiety and inhibit food intake. It also augments the insulin response, inhibits glucagon secretion and slows gastric emptying.

PYY can have an inhibitory effect on gastrointestinal motility and also induces satiety.

Ghrelin is a known orexigenic gut hormone, sometimes referred to as the ‘hunger hormone’. This hormone is suppressed post-surgery.

The biliopancreatic diversion with duodenal switch (BPD/DS)

This procedure is rarely performed in the UK or Ireland due to higher surgical and nutritional deficiency risks involved. Roughly 50 per cent of the stomach is removed (200-250ml remain). The pyloric sphincter remains and the stomach is connected to the last 250cms of the small intestine. The remainder of the small intestine is connected 100cms from the end of the small bowel, forming the common channel where food mixes with digestive enzymes. This procedure results in significant intestinal malabsorption of protein, calories, fat-soluble vitamins (ADEK) and zinc in particular.

Criteria for bariatric surgery


BMI =/>40kg/m2 or 30/35 with co-morbidities (recent onset of diabetes) that can be improved with surgery.

The person commits to the need for long-term follow-up.

All appropriate non-surgical measures have been tried but have failed to achieve or maintain adequate, clinically beneficial weight loss for at least six months.

Fit for anaesthesia and surgery.

BMI>50 — first-line treatment.


Uncontrolled severe psychiatric illness.

Current drug or alcohol abuse.

Uncontrolled eating disorder.

Medically unfit for surgery.


Perioperative care

All suitable patients who meet the inclusion criteria and have had the comprehensive pre-op work up by the MDT should undergo a thorough nutritional and behavioural assessment by a trained dietitian with specific experience of bariatric nutrition. The patient should also undergo eating disorder screening and psychosocial assessment. Binge-eating disorder has been linked to poorer outcomes post-surgery and a cognitive behavioural therapy programme may be indicated before surgery.

It is common for there to be pre-existing nutritional micronutrient deficiencies in obese Class 3 patients prior to surgery, especially ferritin, haemoglobin, vitamin B12 and vitamin D.

In addition to any comorbidity, biochemical measures (HBA1c, lipid profile etc) and a full biochemical assessment should be conducted prior to surgery and annually thereafter (See Table 1). If clinical signs of other deficiencies are present, discretionary measures are indicated. Identified nutritional deficiencies should be corrected, as clinically indicated.

Table 1: Annual biochemical surveillance post-surgery

The pre-op ‘liver-shrinking’ diet

Patients undergoing bariatric surgery are often placed on a two-week, 800kcal, low-fat, low-carbohydrate diet to deplete the liver’s glycogen stores and reduce any liver fat infiltration. This makes the procedures easier and safer for the surgeon.

At this time, the patient is recommended to commence a 100 per cent RNI multivitamin and mineral. The offer of optionally commencing a strong, gut-specific probiotic is also made, as recent research suggests that obese individuals may have disordered gut flora and this could inhibit weight loss post-surgery.

The patient is also recommended to exercise to safe, tolerable levels and be introduced to ‘mindful eating’. This is a cognitive and behavioural approach to meal-times that may aid weight loss maintenance in the long term and minimise symptoms post-surgery.

An alternative of total diet replacement (TDR) in the form of meal replacement sachets can be offered if the patient might struggle to follow the calorie/carbohydrate-restricted pre-op diet.

Post-op nutrition

All patients are required to follow a strict post-op dietary care plan to minimise possible symptoms like dehydration, altered bowel motions, nausea, vomiting, dumping syndrome (RYGB in particular), hair loss, protein energy malnutrition and also to ensure nutritional adequacy.

In addition, 100 per cent RNI vitamin and mineral supplements and calcium/vitamin D supplements are recommended for life. Vitamin B12 injections are given intramuscularly three months post-op routinely in some bariatric centres for RYGP and SG patients due to the lack of intrinsic factor found in the stomach, which helps ‘cleave’ the B12 from the food sources. A proton pump inhibitor is also recommended for six months post-op to reduce the risk of ulcers.

Weeks 0-2 post-op

Liquid diet only; generally high-protein liquids like milk or milk-based liquids are recommended; use of high biological whey protein powder supplements may also be indicated.

Weeks 2-4 post-op

Puréed diet only; pureed or baby food consistency is recommended, again emphasising protein-based foods like fish, chicken, lean meats, eggs and dairy.

Week 4 onwards post-op

Soft diet where the meals will generally be minced, mashed and moist.

In the weeks following the operation, patients are able to manage more solid foods in much smaller portions.

An emphasis on the speed of eating, texture and amounts of foods and fluids is made on an ongoing basis and generally, the dietitian will see the patient five-to-six times over the first year. All patients are offered dietetic consultations annually thereafter, or sooner if there is a particular need. The patient is also encouraged to attend the peer support bariatric groups, where the members of the MDT team can give extra educational sessions.

All patients are encouraged to practice mindful eating and with the aid of the dietitian, to use evidenced-based behaviour modification strategies like self-monitoring (regular weight checks, keeping a food and activity diary) SMART goal setting, and cognitive restructuring (unhelpful thinking styles) to help maintain weight loss, improve quality of life and ensure compliance with supplementation.

Bariatric surgery is a very effective intervention for obesity and obesity-related comorbidities. The procedures are growing in popularity and this may lead to primary care and hospital-based physicians caring for individuals who have had the surgery. Nutritional deficiencies can occur immediately post-op and in the long term and effective biochemical surveillance and micronutrient replacement therapy are essential.

References on request

Case report

A 62-year-old man was referred to the bariatric surgery services by his endocrinologist in 2008. His weight was 131.5kg, BMI 40.1Kg/M2 and WHO BMI classification was obese, Class 3.

His comorbidities included diabetes mellitus, hypertension, dyslipidaemia, fatty infiltration of the liver and chronic back pain with degenerative disk disease.

At the time, his medication included insulin glargine 35 units, oral metformin, antihypertensives and rosuvastatin. He had received three epidurals for back pain.

He presented with significant central obesity and his visceral fat rating was over 30 (very high). Behaviourally, he tended to eat late at night, consume large portions, chose high-energy/sugar snacks and occasionally binged on large amounts of foods over a short period of time. His lifestyle was sedentary, with little exercise. He had tried various forms of weight loss, including commercial weight loss programmes and weight loss medicine. After consultation with the bariatric surgeon and intensive pre-surgery MDT work-up, a laparoscopic Roux-en-Y gastric bypass was performed.

In March 2014, the patient was still off all medications and his weight loss was steady, at 61 per cent of his excess body weight (31kg). He had abdominoplasty for excess skin and is now exercising regularly. He reports much-improved overall quality of life.

He will have yearly biochemistry and follow-up with the bariatric care team and GP, as indicated.

Leave a Comment

You must be logged in to post a comment.

Scroll To Top