Researchers from University of California randomly selected 121 women and divided them into 4 groups. The first group and the second group women can only intake of 1,200 calories per day, one group was needed to record and calculate the calories, the other group doesn’t. The third group intake normal diet and calorie, then keep a record. The fourth group did everything as usual without any changes. The experiment lasted three weeks, researchers measured cortisol levels in these women at the beginning of the experiment and at the end of the experiment. They found that when faced with calorie restriction, cortisol levels in females’ bodies would be elevated. Besides, record the daily calorie intake would also have the same results. "This is the first time we found that reduce calorie intake would increase cortisol levels in humans," Janet said.

It is often nervous if you record the calories every day, so the body will release more stress hormones cortisol, which would make it difficult to reduce weight. "We think this is one of the reasons people can’t lose weight and maintain weight loss." she said, "No matter the way you used to calculate caloric intake, it make your cortex alcohol level rise." Nutritionist Samantha Heller said: "'weight loss is reminiscent of the poverty, hunger, poor, sick, etc. All of them ultimately lead to fail in lose weight. The secret of losing weight is to consume the calories in body greater than the intake of calories. However, strict calorie restriction, diet pills and other means lead to failure. If the rebound happened, people may become more obese than ever before." In order to lose weight, we must firstly develop good habits, including eating a variety of healthy foods, physical activity, planning, keeping patience and so on.

But, for modern people, it is not easy to eat on time with quantitative and eat healthy food. According to a survey from UK, 22% of people had not have the dinner at the table, 30% of them would eat while watching TV, which is harmful to the health. Nutritionist Karen Barber said: " According to our experience, casually eating is the most difficult problem for people who want to lose weight, it is very important to be aware of how much to be eaten to control weight, people are always not good at controlling the balance between healthy eating and weight control.