I know that this is a 100% fact.
I lost 35 pounds inside of a 6 month period, partly due to me working out like riding my bike & what not but mostly due to what & how much I ate.
I use the Loose it app along with Runkeeper on my phone to track my intake & my exercise & was amazed that even though I ate 2400+ calories of good food, I needed to eat more to maintain the 170* weight that I am at now, sometimes depending on my activities of the day I may need up to 4000 calories.
Eating good stuff is the key but part of it is planning so that you can still be eating the right stuff at about the right time so that you get what you need.
For me, my goal was to reduce my sodium & cholesterol intake so that I not only reduce the level of Lisinipril I take for my B.P. but also to lower my risk of needing to take any cholesterol meds. (I hate to take meds.)