Fucoxanthin exerts differing effects on 3T3-L1 cells according to differentiation stage and inhibits glucose uptake in mature adipocytes

► Fucoxanthin enhances 3T3-L1 adipocyte differentiation at an early stage. ► Fucoxanthin inhibits 3T3-L1 adipocyte differentiation at intermediate and late stages. ► Fucoxanthin attenuates glucose uptake by inhibiting the phosphorylation of IRS in mature 3T3-L1 adipocytes. ► Fucoxanthin exerts its anti-obesity effect by inhibiting the differentiation of adipocytes at both intermediate and late stages, as well as glucose uptake in mature adipocytes.