I had followed a rough diet and workout plan last 50 days. Everyday in random time I used MS Excel to record my weight whenever I need to know it. Quickly I realised my weight was not exactly 77 kg when I said to my friend "I am 77kg". In fact, my weight changes all the time, which is reasonable. Everytime I drink a cup of water my scale honestly tells me my weight is about 300 g more than before I had that cup of water, and also everytime I go to toilet or went through a period of time for activities, my weight drops. It also depends on what dress I am wearing. If I wear only shorts, the weight is a bit lower (100-200g) than I I wear trousers. The following chart is the record of my weight fluctuations in the last few weeks.

The small blue dots and line in the chart represents the actually fluctuations of my weight during the time no matter it is day or night, they follow 24hr clock withot interrpution whenever I had a record. The black line in between are sampling line for the last eight records of the weight.
Usually, I workout daily without a break except if I had an injury from the exercise, I can probably take a two day break, but it rarely happens. Everytime I workout I do stripe stepping (Cross Trainer) for one full hour with its cardio program, which maintain my heart rate to 152. It consumes me about 950 Calories. From my unserstanding, 2000 Calories is close to 1kg in the body weight. So, if one lose 1000 Calories he is likely to lose 0.5 kg in his body weight; therefore, I assume myself lose 0.5 kg everytime I do the workout.
It is interesting that no matter how hard you do the exercise, it never returns the same result as you wish, because your body normally provides a sophisticated mechanism to protect itself from extreme changes. In a sense, your body will try to gain back the weight if you workout a lot.
I noticed it very quickly after the first two weeks of my plan, as my weight went back to 78.5 again, which means I need to control my diet as well as the intensity of my exercise. After the second week I start to restrict my diet to proper meals. The way I do this is try not to starve myself and make every meal the same reasonalble amount. For example, I take a bowl of rice, some dishes of meats and vegs, which I normally would require. In this way, my stomach will not expand too much so that I won't suffer from the pain of the emptiness of my stomach.
Few weeks later, I successfully lost nearly 4kg.
Now, except those workouts in the cross trainer, I also do a bit of weighing, a bit of yoga, and sometimes my friend ask me to go for badminton 3-4 times a week. Each time I play about 2 hours. Consider this amount of activities. I can completely know I will not gain excess weight if I sometimes indulge myself with a little bit more of food. Of course, I follow all the previous rules daily and sometimes I take only minimum food I require. Sometimes I even enjoy a little bit of starving. I beleive it is healthy to have short periods of starving because animals do starve from time to time, only not too servere ones.
Please give comments... thanks.