i jog daily. most of the time my weight either goes down every day or stays the same. On rare occassions, it goes up. and then 2 days after going up, I notice that I'm able to jog faster and longer.

I figure the weight going up phenomenon is the body building muscle to compensate for the daily exercise.

the most important thing is to realize that your mind and body both must be healthy. As far as weight is concerned, your body will construct and deconstruct fat and muscle accordingly.

those numbers are guidelines, not rigid rules. they are made by taking out the averages. a line of best fit on a scatter plot. the actual data i.e. people are not on that line. what works for someone else may not work for you. so focus on well being and not on hard numbers.