. >> colleen thompson and ellen shanley are the authors of "fueling the teen machine." so, ellen, how much should the typical teen eat for lunch? >> well, nicolewe measure our intake by our calories. and an active, young man eats about 800 calories for lunch and a young female should eat about 700 calories. >> so, i think you have some examples that bring those numbers to life? >> i do. we have a big mac, a large fry and a large soda. >> mm-hmm. >> and this is about 1,340 calories. and we see with the big mac, we have two burgers, three slices of bread, and their special sauce, which is loaded with calories and fat. >> so that's a lot of calories over here. >> it's a whole lot of calories. >> what do we have over here? >> here is a regular hamburger a small fry, and a small soda. and this is only about 630 calories. so you've been able to cut out half of your calories if you make that choice. >> so since you're within your 700-800 limit, are you able to eat this every day for lunch? >> well, i don't think i'd make that choice. you really are not getting the fruits and vegetables that you need, so there's a lot more nutrition that you should be