Thus, the basal metabolism is reduced. So as you can see, now the restricted amounts of calories that once were causing us to lose fat are not doing the trick. That is why science has suggested that dieting alone may not be the best method to lose fat stores. What's even worse is the person what has only restricted the diet and lost some weight returns to normal eating patterns, the fat returns even quicker that before. So the extra calories are once again, stored as fat.
Activity also effects the energy balance.
By taking physical activity, the BMR increases, so the daily energy needs increase. It is widely accepted that a combination of caloric restriction and exercise is perhaps the soundest method of weight loss. However, it must be remembered that body composition changes must take place slowly in human exercise studies, and the magnitude of the change is small. While the intensity of the exercise may play an important part in appetite suppression, the primary factor involved in weight lose is the total work accomplished. Many have tried to influence thermogenesis by manipulating the ratios of food we consume.