Evening workouts can relax a person after a busy or stressful day. Just make sure not to exercise within two hours of bedtime. Doing so can disrupt your sleep. Under ideal circumstances, it's probably best to exercise before a meal or to wait approximately 90 to 120 minutes after a full meal. After you eat, blood is shifted to the stomach to aid in digestion and exercising muscles compete for blood flow.
Vigorous exercise can sometimes cause an upset stomach or cramping shortly after a meal, too.
Research has shown that exercise also acts as an appetite suppressant, which is further reason to hold off eating until after your workout. Some people, however, are comfortable eating a light snack, i.e., fruit or granola bar, prior to exercising. Do what works best for you. Exercising at a higher intensity does make the body burn more carbohydrate than fat for energy. However, it also expends at least as many fat calories as exercising at a lower intensity in the same amount of time.