1500 kcals for a man your size is a semi-starvation diet, and there are physiological and psychological consequences to semi-starvation diets.
The only people who can withstand (physiologically at least), severe cuts in the caloric intake are those who have a significant amount of body fat, i.e. the obese and morbidly obese, not someone with 25-50 lbs to lose, which is you.
Here is how you calculate the calories you need each day the TDEE (total daily energy expenditure)http://www.iifym.com/tdee-calculator
Figure out what you need and then take 20% off that, and start there, not at some random number you picked because of
If you want the science behind it, then check out exercise physiology textbooks by Katch and McArdle.
You can experiment with your calories, however, at least go with what we know already, not making random shit up.