One of the biggest questions we had when researching whether gastric sleeve surgery was right for us was:
“How much weight can you actually expect to lose?”
We spent countless hours reading through NHS guidance, bariatric clinic websites, Reddit forums, and weight-loss calculators – and what we found was that the answers varied wildly.
So, after 18 months of living with the sleeve, we wanted to put everything we’ve learned into one place – combining the facts we found before surgery with the real numbers and experiences we’ve had since.
Understanding How Gastric Sleeve Surgery Works
To understand potential weight loss, it helps to know what actually changes after the operation.
During gastric sleeve surgery, around 75–80% of your stomach is permanently removed, leaving a narrow, tube-shaped “sleeve” that holds roughly 150–200ml of food – about the size of a banana.
Because your stomach is smaller, you can only eat small portions. But the surgery also removes most of the part that produces ghrelin, the hunger hormone, meaning you often don’t feel hungry in the same way.
This combination – reduced capacity and less appetite – is what makes sustainable weight loss possible.
Before surgery, I (James) could easily finish a full KFC meal. Now, a single mini fillet and a few chips are enough to make me feel full. The change isn’t just physical – it’s psychological too.
What the Research Says About Weight Loss After Gastric Sleeve
According to current NHS and private bariatric data, most patients lose around 60–70% of their excess body weight within 12–18 months.
To explain what that means:
- “Excess body weight” refers to the amount you’re above a healthy BMI (24.9).
- So if your ideal weight is 12 stone, and you start at 20 stone, your excess weight is 8 stone.
- Losing 60–70% of that means losing roughly 5–5.5 stone.
It’s not about perfection or comparing yourself to others – it’s about long-term consistency.
Our Real Progress So Far
We’re now 18 months post-op. At the time of surgery in March 2024, James weighed just over 30 stone, and Kirsten around 18 stone.
- By the one-year mark, James had lost over 12 stone (168 pounds).
- Kirsten had lost 8 stone (112 pounds).
We document this in detail, with photos and monthly weigh-ins, on our Progress Updates pages.
These results are well above the typical averages – not because the surgery worked “better” for us, but because we fully committed to the process before, during, and after surgery.
We also know people who had surgery in the same month as us and have only lost 20–30 pounds total 18 months later. That’s not to shame anyone, but it’s an important reminder:
The gastric sleeve is a tool – not a magic cure.
If you don’t go into this with the right mindset, preparation, and willingness to change your relationship with food, your results will reflect that.
Typical Weight Loss Timeline
While every journey is unique, here’s a general guideline based on medical averages and our own progress:
| Timeframe | Average Progress | Our Experience |
|---|---|---|
| 0–3 months | 30–40 lbs (2–3 stone) | We both lost over 3 stone – mostly from the drastic calorie drop and early recovery. |
| 6 months | 50% of excess weight lost | We were around 66% by this stage thanks to strict routines and regular walking. |
| 12 months | 60–70% of excess weight lost | James had lost 12 stone, Kirsten 8 – both far above expectations. |
| 18–24 months | Weight stabilisation phase | This is where you transition to maintenance and muscle-building. |
Weight loss naturally slows over time as your metabolism adapts and your calorie intake gradually increases – which is normal and healthy.
What Makes the Difference
1. Mindset Before Surgery
We went into this with clear intentions: this wasn’t about quick fixes. We treated it as a lifelong health reset.
Before surgery, we spent months researching, preparing mentally, and planning how we’d handle challenges like food addiction, meal preparation, and cravings. That mental preparation made all the difference when things got tough.
2. Commitment to Lifestyle Change
After surgery, everything changes – how you eat, drink, socialise, and even think about food. If you try to go back to old habits (grazing, takeaways, sugary drinks), the sleeve won’t protect you forever.
We’ve seen this first hand in our surgery support groups. Some people simply couldn’t break those old habits – constant snacking, skipping supplements, drinking calories – and 18 months later, their results reflect that.
3. Exercise and Movement
James started walking daily just a week post-op, eventually progressing to gym workouts.
Kirsten, meanwhile, focused on gentle walking due to health complications from Crohn’s disease, proving that you can still make progress without heavy exercise early on.
4. Consistency With Vitamins and Hydration
This part is absolutely crucial. James hit a wall around month 11 with fatigue, memory issues, and cold intolerance – all caused by nutritional deficiencies. We completely overhauled our supplement plan after that, which you can read about here.
Once we corrected those deficiencies, everything improved – energy, mood, and even recovery.
Maintaining the Results
We’re still working toward the maintenance stage, but we’ve learned that long-term success comes from:
- Listening to your body – Don’t chase numbers. Focus on feeling well.
- Planning meals and prep – It keeps you accountable and portioned.
- Regular check-ins – Weight, body measurements, or even progress photos.
- Staying hydrated and supplementing properly – Small lapses can create big setbacks.
- Having support – Whether it’s a partner, a bariatric group, or online community.
The Bottom Line
Gastric sleeve surgery is one of the most effective weight-loss tools available, but success isn’t guaranteed. It requires the right mindset, preparation, and daily discipline.
If you treat the sleeve as a tool – not a cure – you can absolutely transform your life. We’ve lived it.
For us, it’s been the best decision we’ve ever made. And 18 months later, we’re still learning, improving, and pushing forward.
If you’re about to start your journey, we hope this post gives you a realistic picture of what’s possible – and what it truly takes to get there.
Disclaimer: This post reflects our personal experience and research on weight loss after gastric sleeve surgery. It is not a substitute for professional medical advice. Always speak with your surgeon, GP, or dietitian before making any decisions about your own treatment or recovery.