Chicken meal is basically concentrated, dehydrated chicken. Take 5 lb of wet/fresh chicken, pull out the water and fat and you have 1 lb of chicken meal.
Also, reduced calorie is just formulated to reduce weight. There are other premium foods that are especially formulated for older dogs that have a nutritional balance particularly for seniors.
Overall it's not a bad food, like, well, anything advertised on TV, but it uses canola oil. I won't eat canola so I won't give it to my pets. I happen to *like* sunflower oil in a dog food. It's natural, needs no 'processing' (like soy and canola,) is high in Omega 6 and linoleic acid.
Natural Balance is a pretty good food. You might want to mix in some of their canned to get some more protein variety into it though since the first ingredient is only chicken.
Low Calorie isn't really good though. Usually with low calorie foods, the high calorie things are replaced with more carbs that don't really fill the dog up and make him more hungry. The best thing to do if he's overweight or gaining is just feed him less. He can get the same amount of calories with both food, its just better that the difference is quantity and not quality.