The present invention relates to intra oral devices for treating overweight and obesity by reducing and/or limiting the mouth opening “and/or slowing down the rate of chewing and more specifically to such devices handled by the user with or without the need for professional help, a method and use thereof. Said intra oral device of the present invention consists of a restraining device (8) which is being anchored in the upper and lower jaws, consisting of an elastic element which is inserted into two respective inter-proximal spaces (IPSs) of said upper and said lower jaws and reduces and/or limits the mouth opening and/or slows down the rate of chewing.