Weight loss surgery

Obesity is one of the top contributors to poor health and as rates of obesity continue to increase, the impact on individuals, families and our health system is overwhelming.

Weight loss and 'diets' are some of the most popular internet search terms as we all try to fight the 'battle of the bulge'! One of the most effective treatments if all else has failed is weight loss surgery in certain situations.

  • Weight loss surgery is designed for those who are morbidly obese and have been unable to lose weight and keep it off.
  • It can also be considered for people who are only mild to moderately obese if they have significant health problems.
  • Within New Zealand, some hospitals offer bariatric (weight loss) surgery.
  • Check with your doctor or nurse if this may be an option in your area and what the eligibility criteria are.

Who can have weight loss surgery?

A recent review by the Ministry of Health NZ (2009), confirmed there is strong evidence for the value of bariatric surgery for:

  • people with a BMI of 40 kg/m2 or more
  • a BMI of 35–40 kg/m2 if they have another significant disease (e.g. type 2 diabetes, sleep apnea, high blood pressure or arthritis requiring joint replacement)
  • and if all appropriate non-surgical measures have been tried but failed

BMI (body mass index) gives an indicator of weight to height ratio. BMI is weight in kilograms divided by height in metres squared (kg/m2).  World Health Organization (WHO) recommends people with a BMI of 25–29.9 kg/m2 be considered overweight and a BMI of 30 kg/m2 or more be considered obese. 

To find out what your BMI is use this BMI calculator Centers for Disease Control and Prevention (US).


Deciding to have weight loss surgery is a major decision and requires a life long commitment to healthier eating and living. Weight loss surgery is provided by some District Health Boards. Check with your GP what the criteria are in your area.

  • Your surgeon will discuss the options with you and advise which one is best for your body type, intended weight loss and lifestyle.
  • Although the success rate for most weight loss surgery is high, make sure you understand the risks and what to expect before and afterwards.
  • Complications can include wound infection, bowel leakage, bleeding, stenosis, ulcers and rarely, death.
  • Following surgery, you will need ongoing checks to make sure you don't experience any nutrient deficiency such as B12, folate and iron.

Information from the NZ Clinical Guidelines explains the three bariatric procedures available in New Zealand. All three operations are usually performed by laparoscopy. The operations remove a person’s excess appetite or urge to eat and limit the volume they are able to eat.

  1. Adjustable gastric banding – this places an adjustable band around the person’s upper stomach to create a pouch with 15–30 ml capacity. Saline in the band can be increased or decreased through a port under the skin of the abdomen. The added volume of the band suppresses the person’s appetite, but intermittent refilling is required to maintain that feeling. Adjustable gastric banding can be reversed.
  2. A sleeve gastrectomy removes the outer three-quarters of the person’s stomach and turns the stomach into a long gastric tube or ‘sleeve’. This operation cannot be reversed.
  3. A Roux-en-Y gastric bypass involves changes to the person’s stomach and small bowel. The operation creates a small pouch in the stomach with a narrow outlet. Although the pouch’s capacity can vary, it is usually about 30 ml. A bypass of the small bowel is also created to reduce the absorption of food.

Patient Information

Bariatric Surgey – Information HealthPoint & Auckland DHB, 2014
An Introduction to weight loss surgery NHS Choices (UK), 2014
Laparoscopic Gastric Sleeve Procedure (Weight loss surgery) Bay of Plenty DHB, 2017


Life after weight loss surgery NHS Choices (UK), 2013

Learn more

Obesity related publications Ministry of Health (NZ), 2014 
Weight loss surgery Medline Plus, 2015


  1. Ministry of Health, Clinical Trials Research Unit.  2009.  Clinical Guidelines for Weight Management in New Zealand Adults.  Wellington: Ministry of Health.
  2. Adams TE, Davidson LE, Litwin SE, et al. Health benefits of gastric bypass surgery after six years. Journal of the American Medical Association. 2012; 308: 1122-1131.
  3. Chang SH, Stoll CRT, Song J, et al. The effectiveness and risks of bariatric surgery an updated systematic review and meta-analysis, 2003-2012. JAMA Surgery. Published online 18 December 2013.
  4. Chang SH1, Stoll CR1, Song J2, Varela JE3, Eagon CJ3, Colditz GA1.The effectiveness and risks of bariatric surgery: an updated systematic review and meta-analysis, 2003-2012.JAMA Surg. 2014 Mar;149(3):275-87. doi: 10.1001/jamasurg.2013.3654. [Abstract]
Credits: Written by Health Navigator.