1. Whats your BMI? How tall you are, obviously, has a lot to do with whether your weight is healthyand thats always frustrating for the vertically challenged. At, say, 150 pounds, your weights just right if youre 5 feet 8 inches tall, on the high side of normal if youre 5 feet 6 inches, considered overweight if youre 5 feet 4 inches, and near obese at 5 feet. To figure out if your weight is healthy for your height, calculate your body mass index (BMI). BMI isnt a perfect measure (see question 2 below), but its a great place to start your calculations.

Healthy-weight bonus: The higher your BMI, the higher your risk for diabetes. But lose just 7 percent of your body weight (thats about 10 pounds for a 140-pound woman), and you can cut your risk by 60 percent.

2. Whats your build? Line up 10 women who are all 5 feet 4 inches tall or who each weigh 150 pounds, and youll quickly see why height or weight aloneor even BMIdoesnt always reflect whats healthy. The differences in muscle strength, body shape, and frame size can be astounding.

If youre muscular, your BMI can easily fall into the so-called overweight range because muscle weighs more than fat, says Steven Blair, professor of exercise at the University of South Carolina in Columbia. “By BMI classifications, most football players are obese, Arnold Schwarzenegger is obese, and Serena Williams is overweight. The categories of normal, overweight, and obese are useful for research but not always when it comes to the public.”

Consider your frame size, too. Insurance companies typically divide their weight charts into small-, medium-, and large-frame categories. At 5 feet 4 inches, wearing 1-inch heels, and fully clothed, whats classified as a healthy weight can range from around 115 to 150 pounds, depending upon your frame. Based on your build, you and your doctor can decide if a too-high BMI is OK for your frame or musculature or if its a sign that you need to burn some fatpronto.

Frame-size calculator: The distance between the two little bones on either side of your elbow is used to determine frame size. Hold up your arm at a 90-degree angle with your palm facing your face. Put the pointer finger of your other hand on the bone on one side and your thumb on the other. Then measure the distance between them. Frame sizes are for a women in the 5-foot-4 to 5-foot-7 range.

Distance between elbow bones:
2 2/8 inches and belowSmall frame
2 3/8 inches to 2 5/8 inchesMedium frame
2 6/8 inches and aboveLarge frame

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3. How much have you gained since high school? Its not goofy to want to fit into your old prom dressits healthy. But that dress wont fit if you gain even 10 pounds after high school, a number that experts say is a weight-gain warning point. “Weight gain after about age 20 is really important because most of the weight gain is typically unhealthy fat,” says Walter Willett, professor of epidemiology and nutrition at the Harvard School of Public Health. “If your weight goes up even 4 to 5 pounds, thats when you need to make adjustments. A 10- to 15-pound weight gain, for instance, increases the risk of diabetes appreciably.”

Some women who were fit in high school may be able to add a little padding5 to 10 poundswithout consequences, says JoAnn Manson, MD, chief of preventive medicine at Brigham and Womens Hospital and a professor of medicine at Harvard Medical School. But pick up 20 more, and most of that is fat tissue, not Serena Williams–like muscles.

Keep in mind that genetics may play a role in how much weight you put on, too. If your parents are heavy, gaining weight may be that much easier for youand you may have a predisposition for becoming obese. And its not just one gene playing with your waistline; different genes determine levels of hormones that affect hunger and fullness when you eat. Researchers at the University of Buffalo, the State University of New York, found that people with genetically lower levels of dopamine find food more rewarding than people who genetically have higher levels, so they tend to eat more. Genetics can also play a role in where fat settleson your belly, butt, or hips. Being aware of genetic tendencies helps you work with them.

Keep tabs on your weight by stepping on a scale every day and by cutting calories to either maintain a healthy weight or to drop a few pounds. Shaving 50 calories a day is a good maintenance move; cutting 500 calories a day should help you lose a pound a week.

4. How big is your belly? Waist circumference isnt a weight measurement, per se, but it is a good indicator of whether you have a healthy shape. Being on the upper end of the healthy-weight range for your height may be just fine if, for instance, you have a flat belly. Just as being on the low end may not be enough to offset the risks of carrying a lot of weight around your middle.

Why does waist size matter? The fat that makes your middle resemble an apple is bad news, upping the risk of metabolic syndromea combo of high blood pressure, high triglycerides, high cholesterol, and prediabetes, Willett says. A 1- or 2-inch increase in waist size should be a signal to cut back on calories and add some physical activity to your routine. Bottom line: Womens waists should be no larger than 35 inches; mens, 40 inches max. In fact, experts worry that anything bigger than 32 is bad for you. If you dont like your number, you can target belly fat with the great ab-busting moves in “Your Healthy-Weight Workout Plan.”

Healthy-weight bonus: Reduce your belly fat, and you may reduce your odds of getting cancer. The American Institute for Cancer Research and the World Cancer Research Fund linked excess weight to seven cancersbreast, esophageal, pancreatic, colon, rectal, endometrial, and kidney.

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5. How old are you? Although youll still want to stay within healthy weight and BMI ranges as you get older, you may experience a little creepand thats OK within reason, experts say. In the healthy-weight table used by the Weight Watchers organization, for instance, 134 is the maximum recommended weight for a woman up to age 25 who is 5 feet 4 inches tall. For ages 25 to 45, its 140. When women hit 45-plus, they need to be extravigilant because they start to gain fat and lose muscle due to hormonal changes. If you hit 145 pounds or higher, youll start edging into overweight BMI category, and you dont want to go there.

Healthy-weight bonus: If youre 40-plus and at a healthy weight, youre much less likely to get heart disease as you get older. Pack on the pounds, though, and even if your blood pressures healthy, your heart disease odds go up.

Waist-size calculator: To measure your waist circumference, place a tape measure around your belly an inch above your hip bones. Keep the tape snug and parallel to the floor.

Waist size:
32 inches or belowHealthy
33 to 34 inchesWorry zone
35 inches and aboveDanger zone

6. Is your lifestyle healthy? Even if you still eat Twinkies, exercise will lower your blood pressure, cholesterol, and risks for several cancers. It helps clear blood clots and sets a healthy interval between heartbeats. Plus, it increases muscle contractions, which help regulate blood sugar levels, keeping diabetes at bay.

Youll also be healthierand probably thinnerif you eat lots of fruits, vegetables, and lean proteins. Its as simple as that. “People get too hung up on sticking to the exact details of a diet or finding the right diet,” says Deirdre Leigh Barrett, PhD, assistant clinical professor at Harvard Medical School and author of Waistland: A (R)evolutionary View of Our Weight and Fitness Crisis. “It becomes an excuse for delay. If youre not losing weight, its usually because youre not following the diet, not because its the wrong diet.”

Yunsheng Ma, assistant professor of medicine at the University of Massachusetts Medical School, who studied eight conventional diets, found Ornish, Weight Watchers, and the New Glucose Revolution plans among the healthiest: “The winners emphasize fruits, vegetables, whole grains, and low levels of trans and saturated fats. But you dont really have to follow a plan, just that outline.” And you do need to get moving.