阅读理解

　　We all eat when we are not hungry．If we stopped eating when we were full, we would be thin ,　and chefs would have to find other jobs．You may be tempted to eat when you are bored, tired,　angry or simply sitting in front of food that you feel like putting in your mouth．Don't give in , the diet plans warn．Or, if you must eat , then eat only food that is so unappealing or unsatisfying that it is not worth the effort．

　　It is as important for the sake of losing weight as understanding why there are times when it is extremely important to eat, however, even when there is plenty of food in your stomach．If you find yourself unable to resist snacking and give in and eat a sweet or snack, don't blame your lack of willpower．Your brain is making you do this．

　　This request for carbohydrates , for sweet or starchy(富含淀粉的)food is a signal that an important brain chemical needs to be made．This chemical is serotonin(血管收缩素)its production depends on what you eat or don't eat．When you eat carbohydrates(apart from the carbohydrates in fruit), serotonin is made．When you eat protein, serotonin is not made．

　　Some of us have brains that don't make enough serotonin to last all day, and by late afternoon, we feel the effects of too little of this chemical．We become bored, have difficulty concentrating, lose patience with things that annoy us , and feel tired．Therefore, more serotonin is needed．A food scientist said．“We found out years ago in our research that , at moments like this , the brain sends out a signal saying ‘eat some carbs '．If we pay attention to this message and eat a bar of chocolate or cake , as soon as the snack is digested , serotonin is made and we feel better．”

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