A 0.4kg difference in weight between morning and evening does not usually affect basal metabolism, which may be normal. The amount of food eaten in a day, the amount of water drunk, the number of bowel movements, and whether or not you exercise can all affect the change in body weight. A difference of 0.4kg between morning and evening weight is within the normal range and basal metabolism is generally normal. Basal metabolism refers to the minimum energy consumption required to maintain the human body. Basal metabolism is affected by body surface area, age and gender, in addition, exercise and endocrine factors can also affect basal metabolism. If there is significant weight loss within a month, it is necessary to rule out the presence of diabetes, hyperthyroidism, tuberculosis, malignant tumors and so on. If weight gain is excessive, it may be due to increased cortisol, hypothyroidism and other factors. A difference of 0.4kg between morning and evening weight is within the normal range and is not a cause for concern.