Eat sensibly before exercising says the article on Prevention. Feeling weak and tired will not help with endurance during a workout. The Mayo Clinic suggests eating large meals at least 3-4 hours before a workout and small meals 2-3 hours before a workout. To help your muscles recover, eat both protein and carbohydrates within two hours of exercising.
When I get home I'm always hungry, but want to start the workout as soon as possible and before I can think up excuses why I should spend 20 minutes feeling like I'm pushing a large boulder up hill. So, I've been having a spoonful of peanut butter before starting. It seems to do the trick.