Quote Originally Posted by GLC1968 View Post
Says who? If I work super crazy hard (70%+ of max), I can burn about 400 calories in a hour. That's not much. If I just go about my day with no added formal exercise (bearing in mind that I do farm chores twice a day which is more than a lot of people), I burn AT MOST 1700 calories. If I ate 1500 calories a day, I'd be barely creating a deficit unless I did a LOT of working out.

While I agree that there are absolutely many people out there who eat too little to fuel their workouts and end up throwing off their metabolisms...there are just as many of us out there who eat too much. Metabolism is HIGHLY individual. Making assumptions about what every person burns based on calculations in books or online is about as smart as judging bike fit based on stand-over height. It works for some, but certainly not for everyone.
Geez, talk about making assumptions. Of course I didn't arrive at that amount using an online calculator, and of course that wouldn't be smart. I do think it's possible to burn as much as 600 cals in an hour depending on your activity level, I have done so calculating with an HRM not an online calculator. And I didn't assume anything that's why I suggested a range of 600-1000 for 1 to 2 hours of activity.

But let's use your 400 calories in an hour as an example. If you are eating 1500 calories ( not taking into account the thermic effect of food even), then you have a net of 1100 calories. For most people, this is well below even a basal metabolic rate. I've seen it recommended that a female shouldn't net below 1200 calories. I realize that this number changes as we age, but I don't see how it's a good idea to be chronically on a caloric intake below what's required for functioning.

My only point is that eating too little can actually cause more harm than good by damaging muscle mass and potentially throwing off metabolism.