3500 calories equals about 1 pound. However, you can get 3500 calories and 500% of your daily fat intake. Does that mean you will gain more weight? As far as I can tell, you gain the same amount except you are gaining an unhealthy amount of your calories from fat (losing out on nutrients). Maybe I am mistaken. Second question. I am a male 5'11, 175 (now 170) pounds. I am trying to lose a bit of weight. Last week I lost 2 pounds and gained 1 (ate an entire medium pizza) then lost it again. Yesterday I mowed a lawn for about an hour and a half, had a 30 minute walk, and I walk/jog/ran 40 minutes on a treadmill. I also did about 5 minutes of weights. I ate about 1000 calories if I had to guess (but I drank a ton of water). It is my understanding that you don't burn muscle when there is fat that can be burned. If this is the case, I am wondering how I could have lost so much weight in a day. I have been weighing myself almost daily and never noticed a change more than a pound.