context: To help you lose weight, your doctor might have said things like, " Get more exercise," " Cut back on calories," or " Eat less junk." It's all good advice -- but what exactly does it mean? How much exercise should you do? How many calories do you need to stop eating in order to shed pounds? Learn how to turn your doctor's well-meaning, yet sometimes vague, strategies into real steps you can start taking today. What It Means: For you, gauging a healthy weight might be about how your clothes fit (like whether you can still squeeze into your favorite pair of jeans). For your doctor, getting to a healthy weight has more to do with lowering your odds of getting conditions like type 2 diabetes and heart disease. Keeping an eye on your weight is important. Although some studies have found you can be both overweight and healthy, other researchers say that if the numbers on the scale are high, your health is at risk. Yet stepping on your bathroom scale alone won't tell you if you're at a healthy weight, since it doesn't take your height into account. At 150 pounds, you're overweight if you measure 5 feet 2 inches tall, but just right if you're 6 feet 2 inches. A more accurate measure is your body mass index ( BMI), which calculates your weight in relation to your height. A BMI of between 18.5 and 24.9 is healthy. BMI isn't perfect. It doesn't consider how muscular you are, or where your fat is located. So also check your waist circumference. A woman's waist should measure 35 inches or less, and a man's should be 40 inches or less around. Together, your waist size and BMI can give you a good guide to how much you need to trim. What It Means: Not sure how to get to those numbers? Well, think of it this way: One pound of fat is equal to 3,500 calories. To lose a pound, you need to shave off about 500 calories a day for 7 days. You can do that by cutting calories in your diet and burning calories through exercise. If you trade your usual bag of chips for an apple, swap your grande blended coffee drink for a small iced coffee with skim milk, and hold the cheese on your sandwich at lunch, you could cut 400 calories from your diet. Toss in a 25-minute walk to burn the other 100, and you've skimmed 500 calories for the day. What It Means: You're probably thinking of sodas, chips, and candy. Reframe that idea. Any food that's low in nutrition and high in calories -- including jams and jellies, sauces and gravies -- isn't doing your body any favors. You don't have to stop all splurges. Just cut back on empty calories. Eat smaller portions, less often. Make simple, smart swaps. Bake chicken instead of frying, drink sparkling water instead of soda, and top your pizza with vegetables instead of meat. What It Means: When doctors talk about "whole grains," they mean grains that haven't been refined. The grains in white bread and white rice have had their nutrient-dense outer layers removed. What's left behind is mainly empty carbs. Whole wheat, brown rice, and steel-cut oats have kept their outer layers, which are packed with fiber. That fiber will keep you feeling full for longer, which may be why people who eat more whole grains report greater weight-loss success. Ideally, you want to eat at least 3 ounces of whole grains daily. One slice of whole-grain bread or 1/2 cup of cooked brown rice counts as an ounce. To spot whole grains when you shop, look for "100% whole grains" on the food's label. What It Means: To lose weight, you need to burn off more calories than you take in each day. Part of the formula involves diet. The rest requires exercise. When you need to trim off a few pounds, aim for 60 minutes a day, or 300 minutes a week, of moderate aerobic activity. You don't have to do all 60 minutes at once. Break them up into 10- or 15-minute bursts. If you can ramp up to a higher intensity during those short periods, you may burn fat even more efficiently. Lift weights at the gym or do exercises like sit-ups and pushups at least twice a week to build muscle strength. Stronger muscles boost your metabolism and torch a lot more calories than fat, even when you're not moving. Check with your doctor before increasing your activity level, especially if you have been inactive or have any medical problems.