Avoid caffeinated foods and drinks as much as you can. This is natural and is found in leaves, seed and fruits of more that 63 species of plants and other kinds of compounds commonly known as Methylxanthesis.Coffee cocoa beans, cola nuts, and tea leaves are the common known sources of caffeine. It is a pharmacologically active substance and depending on the dose can be a mild stimulant to the nervous system. Caffeine in this case does not does accumulate in the body because it is excreted after few hours. It is toxic in large doses. Caffeine has the ability to speed up the phentermine without prescription pills excretion from the body and this is why phentarmine takes less time to suppress your appetite.In a human brain, the feeding center is responsible to inform your body that you are full or not are under the control of neurotransmitters. Neropinephrine is the increase in the level of neurotransmitters in the body and dopamine suppresses the feeding center. The increased Neropinephrine in the satiety center stimulates eating while serotonin suppresses the appetite. From a research it is believed that, phentermine and other doses available to the body are due to the limitation in the amount of Neropinephrine in the human nervous system. Others also believe that the repetition of stimulation reached through the response of phentermine and Neropinephrine. Another theory is that, the body is able to metabolize and phentermine more and more again as time passes by. The therapeutic effect in this case may not be achieved due to eventual metabolism that is rapid and blood levels are not maintained long enough.