I've been running 90-100mpw and eating less than I did a year ago when I was running 70mpw. Back then my weight naturally decreased to about 152lbs. I did not lose weight all summer despite eating very little, and the past 6 weeks or so I've actually been gaining weight. I've gained about 6lbs in 6 weeks. After thinking I might be overestimating my caloric intake, I started closely monitoring everything I consumed and found I was eating 2500-3000 calories most days, some days as little as 2000 calories if I ate more than 3000 the day before. This is with running 12-16 miles a day and walking another hour or so a day (I walk to and from campus, etc). I don't really understand how that's possible. I have been feeling more tired than usual in that 9-10 hours of sleep is easily doable, but I don't know if that's related to my physiology or just the fact I've been running more. I've run and lost weight before and I'm very conscious of what I eat. Never have I eaten this little for the amount of running I'm doing. I also will add that I don't feel like I'm starving myself at all and often awake feeling like I actually ate too much the night before.
Can anyone comment on how many calories someone like myself would be expected to need, and how likely it is that I have some metabolic disorder? Even 3000 calories/day seems like it'd be low for someone running 90mpw and walking another 2-4 miles/day.