Method for treating hair fibers

A method for treating hair fibers to change the shape of the hair fibers without excessively altering the hair color and/or without excessively damaging the hair fibers, said method comprising:

• applying to the hair fibers at least one reducing composition, free of ceramide, comprising at least one reducing agent, wherein the at least one reducing agent is chosen from thiols and wherein
• when the at least one reducing composition does not comprise at least one aminothiol compound, the at least one reducing agent is present in an amount of less than 3% by weight, relative to the total weight of the at least one reducing composition,
• when the at least one reducing composition does comprise at least one aminothiol compound, the at least one reducing agent is present in an amount of less than 5% by weight, relative to the total weight of the at least one reducing composition, and
• applying a heating iron to the hair fibers to raise the temperature of said hair fibers, wherein said heating iron has a temperature of at least 60° C., and wherein the heating iron is applied before or after the hair fibers are optionally rinsed, and
• thus changing the shape of the hair fibers without excessive alteration of the hair color and/or without excessive damage to the hair fibers, and without a fixing step.