Compare bariatric surgery options: gastric bypass, sleeve gastrectomy, and gastric band. See expected weight loss, timelines, and eligibility by BMI.
Bariatric surgery is the most effective long-term treatment for severe obesity, but choosing the right procedure requires understanding the differences in expected outcomes, risks, recovery, and lifestyle changes. The three most common procedures — Roux-en-Y gastric bypass (RYGB), sleeve gastrectomy (VSG), and adjustable gastric band (LAGB) — each offer different profiles of weight loss effectiveness, complication rates, and reversibility.
Weight loss after bariatric surgery is measured in Excess Weight Loss percentage (EWL%), calculated as the percentage of weight above a BMI of 25 that is lost. At 2 years post-surgery, typical results are: gastric bypass 60–80% EWL, sleeve gastrectomy 50–70% EWL, and gastric band 40–55% EWL.
This calculator helps you compare expected outcomes across all three procedures based on your current BMI, providing realistic timelines and helping you have an informed discussion with your bariatric surgeon. Whether you are a beginner or experienced professional, this free online tool provides instant, reliable results without manual computation.
Choosing bariatric surgery is life-changing. This calculator provides side-by-side comparison of expected outcomes so you can have a more informed conversation with your surgical team about which procedure best matches your goals and medical profile. Having a precise figure at your fingertips empowers better planning and more confident decisions. Manual calculations are error-prone and time-consuming; this tool delivers verified results in seconds so you can focus on strategy.
BMI = weight(kg) / height(m)² Excess Weight = Current Weight − Weight at BMI 25 EWL% = (Weight Lost / Excess Weight) × 100 Typical EWL% by Procedure (2-year outcomes): • Gastric Bypass (RYGB): 60–80% EWL • Sleeve Gastrectomy (VSG): 50–70% EWL • Gastric Band (LAGB): 40–55% EWL Eligibility: • BMI ≥40 (or ≥35 with obesity-related comorbidities) • Failed prior non-surgical weight loss attempts
Result: BMI 45.6 | Excess weight: 135 lbs | Bypass: 81–108 lbs | Sleeve: 68–95 lbs | Band: 54–74 lbs
At 300 lbs and 5'8", BMI is 45.6 with 135 lbs of excess weight (above BMI 25 = 165 lbs). Gastric bypass at 60–80% EWL = 81–108 lbs lost, reaching 192–219 lbs. Sleeve at 50–70% EWL = 68–95 lbs lost, reaching 205–232 lbs. Band at 40–55% EWL = 54–74 lbs lost, reaching 226–246 lbs. These results typically occur over 12–24 months with peak weight loss at 12–18 months for bypass/sleeve.
EWL% is the standard metric for bariatric surgery outcomes, not total weight loss. It's calculated as: (Weight Lost / Excess Weight) × 100, where excess weight is everything above a BMI of 25. A patient starting at 300 lbs with an ideal weight of 165 lbs has 135 lbs of excess weight. If they lose 95 lbs (reaching 205 lbs), their EWL% is 70%. This metric allows fair comparison across patients of different starting sizes.
Gastric bypass creates a small stomach pouch and reroutes the intestines, causing both restriction and mild malabsorption. It has the highest weight loss but is the most complex surgically. Sleeve gastrectomy removes ~80% of the stomach, creating a banana-shaped tube. It's restriction-only with no intestinal rerouting. The gastric band places an adjustable silicone ring around the upper stomach to limit food intake. It's the least invasive but least effective.
No single procedure is best for everyone. Your bariatric surgeon will consider: your BMI, medical conditions (especially diabetes and GERD), eating patterns, surgical history, and personal preferences. The best surgery is the one that your surgical team recommends based on YOUR specific medical profile and that you can commit to following long-term.
Standard eligibility criteria: BMI ≥40, or BMI ≥35 with at least one obesity-related comorbidity (type 2 diabetes, sleep apnea, hypertension, etc.), or BMI 30–35 with poorly controlled type 2 diabetes (for metabolic surgery). You must also have documented failure of non-surgical weight loss attempts. Some programs require a 6-month supervised diet before approval. Insurance requirements vary by provider.
All three procedures are generally safe when performed by experienced surgeons at accredited centers. The 30-day mortality rate is approximately 0.1–0.3% for all procedures. Sleeve gastrectomy has slightly lower short-term complication rates than gastric bypass. Gastric band has low surgical risk but higher long-term revision rates (up to 50% at 10 years). Overall, sleeve gastrectomy is currently considered the best balance of effectiveness and safety.
Weight loss is fastest in the first 6 months: typically 3–5 lbs/week for bypass, 2–4 lbs/week for sleeve, and 1–2 lbs/week for band. Weight loss slows significantly after 6 months and typically plateaus at 12–18 months for bypass/sleeve and 18–24 months for band. Most patients reach their nadir (lowest weight) at 12–18 months post-surgery.
Yes. Weight regain is common, particularly after 2–5 years. Studies show 20–30% of patients regain significant weight (>50% of lost weight) within 5–10 years. Factors that contribute: stretching of the gastric pouch/sleeve, hormonal adaptation, return to high-calorie eating patterns, and decreased physical activity. Long-term dietary compliance and regular follow-up with your bariatric team are essential for maintaining results.
All procedures require lifelong vitamin and mineral supplementation. Gastric bypass has the highest risk of nutritional deficiencies (iron, B12, calcium, vitamin D, folate) due to malabsorption. Sleeve has moderate risk. Band has the lowest nutritional impact but still requires monitoring. Protein intake of 60–80g/day is essential for all procedures. Most patients need to eat 4–6 small meals daily rather than 3 large meals.
Type 2 diabetes remission: 60–80% (bypass), 50–70% (sleeve), 30–50% (band). Hypertension improvement: 60–70% of patients. Sleep apnea resolution: 70–80%. GERD: improves with bypass, may worsen with sleeve. Joint pain significantly reduces. Fertility often improves. Depression symptoms improve in 50–60% of patients. Overall, bariatric surgery reduces 10-year mortality by approximately 30–40%.