How much over weight do you have to be before you can have a gastric sleeve surgery performed?

It's extremely: variable, depending upon age, weight, overall health, comorbid conditions, etc. Check w/your doctor re: a referral to a bariatric surgeon for an evaluation.

Gastric sleeve: Generally you need to have a BMI(body mass index) over 40 or 35 with co-morbidities of obesity ( poorly controlled diabetes, difficult to control hypertension) before a bariatric surgeon would consider you a candidate.

Sleeve gastrectomy: You need to have a BMI over 40 if you have no medical problems, or a BMI over 35 if you have at least 2 obesity related medical problems.