Background and Objectives Weight reduction has evidenced benefit on attenuation of histological activity and fibrosis of nonalcoholic steatohepatitis (NASH), but there is scarcity of data for lean NASH subgroup. We have designed this study to compare the effects of weight reduction on histological activity and fibrosis of lean and non-lean NASH. Methods We have included 20 lean and 20 non-lean histologically proven NASH patients. BMI < 25 kg/m2 was defined as non-lean. Informed consent was taken from each subject. All methods were carried out in accordance with the Declaration of Helsinki. Moderate exercise along with dietary restriction was advised for both groups for weight reduction. After 1 year, 16 non-lean and 15 lean had completed second liver biopsy. Results Age, sex, alanine transaminase (ALT), aspartate aminotransferase (AST), gamma-glutamyltrasferase (GGT), Homeostasis model assessment insulin resistance (HOMA-IR), triglyceride and high density lipoprotein (HDL) was similar in both groups. Steatosis, ballooning, lobular inflammation, nonalcoholic fatty liver disease activity score (NAS) and fibrosis was similar in the two groups. In lean/non-lean group, any amount of weight reduction, ≥ 5% weight reduction and ≥ 7% weight reduction was found in respectively 8/11, 5/6 and 2/6 patients. In both lean and non-lean groups, weight reduction of any amount was associated with significant reduction of steatosis, ballooning and NAS, except lobular inflammation and fibrosis. In both groups, weight reduction of ≥ 5% was associated with significant reduction in NAS only. However, significant improvement in NAS was noted with ≥ 7% weight reduction in non-lean group only. Conclusion Smaller amount of weight reduction had the good benefit of improvement in all the segments of histological activity in both lean and non-lean NASH.