Background: Obesity-induced alterations in biomechanics and muscle recruitment during activities of daily living, such as sit-to-stand (STS) are often attributed to increases in adipose tissue (AT) mass. Central or peripheral distribution of AT may differently affect biomechanics and muscle recruitment. Methods: Fifteen healthy, normal weight (BMI 22.4 ± 1.9 kg/m2, 24.1 ± 4.2 years) subjects volunteered. External loads equivalent to a 5 kg/m2 BMI increase were applied in three conditions: unloaded (UN), centrally loaded (CL), and peripherally loaded (PL). Subjects completed three successful STS movements in a backless chair under each load condition in random order. Motion analysis and lower extremity surface electromyography (EMG) were measured. Results: Compared to UN and CL, PL significantly increased support width during STS. PL also significantly increased maximum trunk flexion compared to CL. Peak and total VM EMG activity were significantly increased during CL, compared to UN and PL. During CL, peak VL EMG activity was significantly greater than UN. Conclusions: Central and peripheral weight gain induce different biomechanical adaptations during STS. Central weight gain increases knee extensor muscle activity during STS independent of biomechanical changes. In contrast, peripheral weight gain increases support width and trunk flexion with minimal EMG changes during STS.