We investigated the effect of acupuncture therapy on obese women's body weight and peripheral blood levels of serum immunoglobulin G (IgG), immunoglobulin A (IgA), immunoglobulin M (IgM), and immunoglobulin E (IgE). Sixty-three healthy women were assigned into 3 groups: placebo electroacupuncture (n = 13; mean age, 40.5 +/- 4.2 years; body mass index [BMI], 33.5 +/- 4.2), diet restriction (n = 23; mean age, 42.9 +/- 4.0 years; BMI, 34.6 +/- 2.9), and electroacupuncture (n = 24; mean age, 40.1 +/- 5.9 years; BMI, 33.9 +/- 2.7). Electroacupuncture was applied to the Hunger and Shen Men ear points and to the LI 4, LI 11, St 36, St 44, and Ren 6 body points for 30 min once daily for 20 days. A restricted diet of 1400 kilocalories was given to participants in all 3 groups for 20 days. Weight was lost significantly in subjects in the electroacupuncture group compared to those in the diet restriction and placebo electroacupuncture groups (p < 0.000, Tukey test). Modulations in serum IgG (p < 0.001) were apparent in women treated with electroacupuncture compared with women treated with placebo electroacupuncture and restricted diet only. No significant changes were seen in serum IgA, IgM, and IgE levels among the 3 groups. Our results suggest that electroacupuncture can be effectively used to treat obesity. We also observed a modulating effect of serum IgG, which is associated with weight loss, in patients in the electroacupuncture group.