Your metabolism has probably evened-out and tends to be immune to quick overhauls. Instead, make slow, steady changes. Change your diet to include the energy foods outlined earlier. Take a walk every day during your lunch break and then start adding more exercise. Focus on raising your metabolism and giving yourself energy and, remember, you’re 40, but you aren’t dead. You want to give yourself the best chance to stay healthy, stay fit, and be around to enjoy the next 40 or so years of your life.