Energy Consumption

Is it true a person's daily energy consumption is almost fix at certain level? For instant a person who used to exercise everyday will have a higher daily energy consumption than those who doesn't?

From conversation with other gym members, it was told that a person who normally exercise on regular basis will tend to have higher energy consumption even if he doesn't work out! Example is if a normally work out person will consume 1800 kcal per day without work out, as compare to a normal person who only need around 1000 kcal - 1200 kcal per day.

That explain why a highly energitic person tends to take more food than those doesn't. And if the person stop workout for some time, he/she will tends to put on weight easier than others.

My conclusion is: I stopped workout for 2 months, and still consuming similar amount of food everyday and I gained about 5 kg in 2 months. Last week I went back to gym, and until last Thursday (which is exactly 9 days after restarting) i lost 3 kg. I am happy that I manage to shredd off extra pounds of weight by continuing exercising, and my target is to lose another 3 kg to 5 kg within the next 3 weeks.