A treatment system for cooling subcutaneous lipid-rich cells in a subject, comprising: an applicator configured to be in thermal communication with skin of the subject; and a control unit having a cooling state and a heating state, the control unit including an applicator circulation circuit including a mixing reservoir configured to receive and hold chilled coolant, a supply end in fluid communication with the applicator, and a return end in fluid communication with the applicator, the applicator circulation circuit defining a flow path extending between the supply end and the return end and along which coolant flows to deliver coolant to the applicator, a chiller apparatus configured to chill coolant from the applicator circulation circuit, the chiller apparatus is configured to chill a volume of coolant and deliver the pre-chilled coolant to the mixing reservoir of the applicator circulation circuit to reduce a temperature of a volume of coolant held in the mixing reservoir of the applicator circulation circuit from room temperature to a temperature less than about 0°C such that coolant from the volume of chilled coolant in the mixing reservoir cools the applicator to a temperature at or below 0°C when the control unit is in the cooling state and while coolant in the chiller apparatus is maintained at a temperature less than about 0°C, and a heater apparatus configured to deliver heated coolant to the applicator circulation circuit to raise the temperature of the coolant in the applicator circulation circuit when the control unit is in the heating state. an applicator configured to be in thermal communication with skin of the subject; and a control unit having a cooling state and a heating state, the control unit including an applicator circulation circuit including a mixing reservoir configured to receive and hold chilled coolant, a supply end in fluid communication with the applicator, and a return end in fluid communication with the applicator, the applicator circulation circuit defining a flow path extending between the supply end and the return end and along which coolant flows to deliver coolant to the applicator, a chiller apparatus configured to chill coolant from the applicator circulation circuit, the chiller apparatus is configured to chill a volume of coolant and deliver the pre-chilled coolant to the mixing reservoir of the applicator circulation circuit to reduce a temperature of a volume of coolant held in the mixing reservoir of the applicator circulation circuit from room temperature to a temperature less than about 0°C such that coolant from the volume of chilled coolant in the mixing reservoir cools the applicator to a temperature at or below 0°C when the control unit is in the cooling state and while coolant in the chiller apparatus is maintained at a temperature less than about 0°C, and a heater apparatus configured to deliver heated coolant to the applicator circulation circuit to raise the temperature of the coolant in the applicator circulation circuit when the control unit is in the heating state. an applicator circulation circuit including a mixing reservoir configured to receive and hold chilled coolant, a supply end in fluid communication with the applicator, and a return end in fluid communication with the applicator, the applicator circulation circuit defining a flow path extending between the supply end and the return end and along which coolant flows to deliver coolant to the applicator, a chiller apparatus configured to chill coolant from the applicator circulation circuit, the chiller apparatus is configured to chill a volume of coolant and deliver the pre-chilled coolant to the mixing reservoir of the applicator circulation circuit to reduce a temperature of a volume of coolant held in the mixing reservoir of the applicator circulation circuit from room temperature to a temperature less than about 0°C such that coolant from the volume of chilled coolant in the mixing reservoir cools the applicator to a temperature at or below 0°C when the control unit is in the cooling state and while coolant in the chiller apparatus is maintained at a temperature less than about 0°C, and a heater apparatus configured to deliver heated coolant to the applicator circulation circuit to raise the temperature of the coolant in the applicator circulation circuit when the control unit is in the heating state.