Well I would question what he is saying, I have been eating fruit all my life, just to be truthful I hate sweets. I'll have 4 apples in a day, 2 for breakfeast and another 2 during the rest of the day. I could even eat 5 peaches in a day too. It has to do with your body if you can burn food off or not. Not to do with having an apple here and there.
I'm not overweight or even close to it because I was lucky enough to have a body that burns off food at an extremely fast rate so I get all the good stuff and leave non of the fat behind.
One thing I have read though it's not eating less food that gets your skinny its your body for one and the type of food you eat. Just eat stuff like brown rice, beans, vegies, fruits and cut back on eating out, meats, and high fat stuff. Even the Cheif Boy R D stuff people love so much, or K-D.
Just because he's a Trainer doesn't me he knows best.
Just rember if your willing to come here to question it you know yourself there may be no truth to it what so ever. Well Good luck with your weight loss but most of all just enjoy life and not worry so much on getting the food in right between work outs, just make foods that are healthy and fun.