Expected Weight Loss

Many people go into weight loss surgery with the goal of getting to what is considered a healthy BMI. The reality of weight loss surgery, however, is that many people will settle at a long-term weight that is above the standard healthy BMI range. Despite many people having the perception of reaching a healthy BMI as the definition of success, the real goal of weight loss surgery is to actually just lose a good amount of weight and keep it off. A successful surgery is one where your weight loss achieved has improved your physical and emotional health and wellbeing and is realistic for you to maintain.

The average total body weight loss of the most regularly performed weight loss surgery procedures are listed below:

  • Sleeve Gastrectomy – 20-30% total body weight loss
  • Roux-en-Y Gastric Bypass – 23-25% total body weight loss
  • Single Loop/Mini/One Anastomosis Gastric Bypass – 32-38% total body weight loss

Having this level of weight loss may get some people into the healthy BMI range, but certainly not everyone. There will then always be those people who lose a lot more than this and those who lose less.

The amount of weight loss someone achieves can be impacted by the following:

Type of weight loss surgery procedure:

As can be seen above, different weight loss surgery procedures can yield different average total body weight loss.

Primary vs revisional procedure (e.g. primary bypass vs converting from a gastric band to a bypass):

Weight loss tends to be lower and slower in revisional procedures when compared with primary procedures.


People who are older than 50 years of age tend to have less weight loss than those who are under 50 years of age.

Medical background:

Certain medical conditions and medications can slow the rate of weight loss.


Research has shown that some people genetically respond better to the surgery than others. Chances are, if you have had a blood relative do well with the surgery, you are likely to do well too. A lot of this comes back to how your body hormonally responds to the surgery, in particular changes to the regulation of your appetite hormones (ghrelin and leptin).

Lifestyle choices – diet and exercise:

Ultimately weight loss surgery is a tool and not a stand alone quick fix. No weight loss surgery procedure is immune to weight plateau’s and weight regain. Weight loss surgery makes it more achievable to implement the required lifestyle changes – not replace the need for them.

It is very important to have an open and honest conversation with your Dietitian and Surgeon about realistic weight loss expectations for you at your pre-operative appointment. As cliche as it sounds, everyones weight loss surgery journey is different, so try to avoid comparing yourself to others and just focus on you!

Most people will reach a weight loss plateau at about 12-15 months post-surgery. This is usually when the ‘honeymoon’ phase of the surgery has passed, and your body is starting to adapt to the physiological changes induced by the surgery. From here on in weight loss is harder and more up to the choices you make with regards to nutrition and exercise. Keeping in regular contact with your Dietitian in the first 12 months post surgery will help to optimise your weight loss achieved in this integral time frame when your body is most responsive to weight loss. Continuing to see your Dietitian beyond 12 months will help to keep your weight loss off and minimise weight re gain once you are pass the honeymoon phase and good nutrition and exercise are key!

– Jacinta

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