I have determined that when I swim, based on my heart rate, I am burning an enormous amount of calories. The other day, I wore my HR monitor and based on my average HR, time spent swimming, and my weight, I burned 1053 calories. Now, the next day, I ran for 40 minutes and burned 453 calories.
I have noticed that when I just swim over a number of weeks, my LDL cholesterol readings go up and my body fat goes up as well. When I just run and don't burn as many calories (according to my HR monitor) my LDL drops, my HDLs go up, and my body fat decreases. I've noticed this now over the course of 13 years.
Anybody know of any studies out there that might explain this? Why would an activity such as swimming that obviously burns a bunch of calories cause an increase in body fat?