Preeclampsia may be due to an excess of circulating anti-angiogenic growth factors derived from the placenta, but metabolic syndrome-like disorders may also set off a cascade of placental and systemic inflammation and oxidative stress. We present a case of severe superimposed preeclampsia with obesity, diabetes and a mild imbalance of angiogenic factors, in which diet therapy ameliorated the preeclamptic signs while improving the adiponectin level. A 41-year-old pregnant woman with obesity and diabetes was referred to our hospital because of severe proteinuria and hypertension at 22 weeks of gestation. After administration of insulin and hydralazine with diet therapy, her hypertension and proteinuria were ameliorated with a 15-kg weight loss. Her adiponectin level was low and her leptin level was high, but her angiogenic factor levels were within the normal ranges for pregnant women at admission. The diet therapy ameliorated her hypertension and proteinuria while improving her adiponectin level as she achieved weight loss. This case suggests that diet therapy for obese preeclampsia patients with a mild imbalance of anti-and pro-angiogenic factors may play an important role in managing preeclampsia. Measurements of maternal adipocytokines and angiogenic factors may be important to distinguish the main cause of preeclampsia, i.e., poor placentation or maternal constitutional factors, for managing preeclampsia in patients with obesity.