It happens that another rookie, started training, in spite of its very nature tends to resemble some sort of athlete who belongs to a different type of addition. 
Change the inherent constitutional type is impossible. At best you can only lead to a harmonious body weight according to its proportions. 
Check if your weight (body weight) norm. To this end, the weight (in kilograms) divided by height (in decimetres). The result of the division within 4,3-3,2 indicates normal weight, 5,3-4,4 - excessive and 3,1-2,8 - inadequate. It is clear that the data hypersthenics and asthenics will be closer to the extreme boundaries, whereas normostenikov be located somewhere in the middle. Indicators above or below the limits indicated either on morbid obesity, or depletion, and in both cases it is necessary to see a doctor.
Usually the first 2-3 weeks strength training is a slight decrease in body weight, which is associated with a decrease in body fat. Then the weight stabilizes and then begins to slowly increase due to muscle mass. Losing weight is greater than 2 - 3 pounds - a sign of a back-breaking loads, or disease.