America's roads have become crowded with runners: In 2011, 7.6 million women completed U.S. road races, including about 3 million 5K finishers, according to Running USA's 2012 State of the Sport report. Some women start running mainly to lose weight, while others are looking to see how fast they can rattle off a 5K. There is no reason, however, why you can't shrink both your dress size and your 5K personal best at the same time.
Set Your Targets
Pick a 5K race at least 12 weeks away if you're an experienced runner and as far as six months away if you're just getting started.
Formulate a safe and healthy weight-loss goal. You can rely on published "ideal weight" tables and metrics like the body mass index, or BMI, for help in this area, but recognize that your individual frame, tendency toward muscularity and a host of other factors determine what "ideal" is for you.
Select a time goal for your 5K if you've run one before. If you have no idea how fast you can reasonably expect to run, or have a goal of just finishing in one piece, that's fine -- you can settle on a target time along the way or not worry about it at all.
Calculate how many pounds a week you need to lose to reach your goal by race day. If you need to lose more than 2 pounds a week, either focus your sights on a 5K further down the road or choose a more modest weight-loss goal.
Training for the 5K
Research 5K training plans online, or, if you have some know-how, design your own. Whatever you pick or concoct, be sure that it includes a bare minimum of three runs per week at least three miles long; a total of at least 20 miles a week of running and walking is preferable.
Ensure that your plan meshes with your desired rate of weight loss. Losing 1 pound means burning 3,500 calories. Assume that you will burn roughly 100 calories per mile of running and that dietary changes alone will result in a pound or two a week of weight loss.
Incorporate walking breaks into your runs for the first month if you need to, and concern yourself first and foremost with completing the distance, not your speed.
Eliminate obvious sources of excess, not nutritive calories from your diet, such as candy, desserts, alcohol, nondiet soda, cream sauces, dressings and marinades containing oil, and butter. Hey, sounds like a tall order, but you can do it -- many others have.
Add more nutrient-dense, fiber-rich foods such as fresh vegetables to your regimen, and use low-calorie favorings such as vinegar, soy sauce and spices to boost their appeal.
Enlist a dieting buddy for the duration of this period. Partnership can do wonders for personal resolve.
L.T. Davidson has been a professional writer and editor since 1994. He has been published in "Triathlete," "Men's Fitness" and "Competitor." A former elite cyclist with a Master of Science in exercise physiology from the University of Miami, Davidson is now in the broadcast news business.