Roughly 100 calories a mile is a good way to gauge it. But, yes, it depends on speed and intesity. Where a bunch of people go wrong to include myself, you do a good cardio session and binge the next meal. You think you earned it because you worked out. Thats a no-no. You buddy is also right, but, he is a bodybuilder. Different lifestyle altogether. These guys try to take in 1 to 1.5 grams of protien per pound of bodyweight. This seems like a ton, but you will have a full feeling throughout the day. I am not bragging but I am going to use myself and what I do. Its just a model. I take in 4-6 shakes a day. I use only a few tyep of supplements and rarely ever do I use fatburners. Your friend has not mentioned that you can take in to much protien and store it as fat if you are not hitting the gym regularly. Bodybuilders try to keep a high balance of nitrogen with all the protien. This is technical, but easy to achieve. Water consumption- this will help you stay full all day as well. I use crystal light to flavor the water. You will feel watery but its just in your head. Its also a natural diauretic. Lastly, I write all my food intake down. Yup, sounds OCD, but you can't BS yourself. Eat strict/healthy for 6 days and on the 7th, have a cheat day. If you crave sweets, eat some, just in moderation. Basically, you are carb deprived and your body needs sugar. Hope this helps, we can get into when and what to take for pre and post workout if you want. Let me know.