Table 1. Study characteristics.

Author (year)	Study design	Study population	Surgery and diagnosis percent (n/N)	Preoperative body weight/body mass index (BMI) percent (n/N)	Follow up mean time, percent (n/N)
Garcia (2008)	Retrospective cohort	N = 63 male: 59% age: mean 53.4 ±8.1 years (36–65)	Lumbar decompression with or without fusion: Stenosis: 100 (63/63)	Mean preoperative Body weight: 92.3 ±16.2 kg BMI: 31.0 ±4.7 kg/m2 Weight classification*: Overweight: 50.8 (32/63) Obese: 27.0 (17/63) Morbidly obese: 22.2 (14/63)	34.4 months (24–51.3 months), 100 (63/63)
Vaidya (2009)	Retrospective cohort	N = 63 male: 40% age: mean 53 years (28-81)	Lumbar decompression and fusion: Stenosis: 50.8 (32/63) Degenerative disc disease: 22.2 (14/63) Revision surgery for post laminectomy instability: 12.7 (8/63) Spondylolisthesis: 7.9 (5/63) Degenerative scoliosis: 6.3 (4/63)	Mean preoperative Body weight: 103.9 kg (68–158.7 kg) BMI: 36.4 kg/m2 (30–53 kg/m2) Weight classification†: Obese: 50.8 (32/63) Morbidly obese: 49.2 (31/63)	20.4 months (14–37 months), 92 (58/63)

^*Overweight > 25 < 30; obese BMI ≥30 <35; morbidly obese BMI ≥35

^†Obese BMI >30 < 39 and no comorbidity; morbidly obese, BMI > 30 <39 with morbidity or BMI >40 and no comorbidity