There is disclosed a dietary supplement composition of alkaloids and flavonoids extracted from citrus fruits that exhibits lipolytic and thermogenic activity and increases RMR, while at the same time exhibiting no negative side effects such as increase in blood pressure or heart rate. The composition essentially comprises two components: (A) the protoalkaloids synephrine, tyramine, N-methyltyramine, hordenine and octopamine; and (B) at least one of hesperidin, naringin and mixtures thereof.