smoking did affect our metabolism and in order to counteract the change when you quit you need to lower your caloric intake by 150-200 calories per day.
A good way to keep up your energy level is to eat 6-8 small meals per day.
An orange and a piece of cheese
A banana and two bites of chicken or other protein.
The fruit (orange, banana, strawberries, watermelon, frozen grapes) raises your blood sugar and energy level while the protein holds it there..
Eating frequent small meals keeps your metabolism in fat burning mode. Dieting puts your metabolism in fat storing mode.
Sparkpeople has good exercise videos for all stages of ability even, physically disabled.