To help you learn how to eat healthfully, start with the U.S. Department of Agriculture's (USDA) dietary guidelines system, which you can find at http://www.mypyramid.gov. The MyPyramid system, which looks somewhat like the familiar food pyramid of old, offers guidance based on individual needs and replaces "serving" recommendations with actual amounts of food. It also emphasizes the importance of balancing nutritious (and tasty!) food choices from all food groups every day with daily physical activity.
Carbohydrates should provide 45%–65% of your daily calories. Most of those calories should come from the complex carbohydrates in high-fiber and unrefined foods, such as bran cereal and other whole-grain products, brown rice, beans and other legumes, and many fruits and vegetables. These carbohydrates are digested and absorbed slowly, so they raise the blood sugar gradually and don't trigger a large release of insulin. People who eat lots of these foods have higher HDL ("good") cholesterol levels and a lower risk of obesity, diabetes, and heart disease. A good amount of soluble fiber in the diet lowers LDL ("bad") cholesterol, and high-fiber diets reduce the risk of intestinal disorders ranging from constipation and diverticulosis to hemorrhoids. Some studies have shown that fiber may help reduce the risk of colon cancer. Men need more fiber than women: 38 vs. 25 grams a day before the age of 50 and 30 vs. 21 grams a day thereafter.
Low-fat diets also can help you lose weight.16 But the amount of weight lost is usually small. You can lose weight and lower your risk for heart disease and stroke if you follow an overall healthy pattern of eating that includes more fruits, vegetables, whole grains and beans that are high in fiber, nuts, low-fat dairy and fish, in addition to staying away from trans fat and saturated fat.
If you lose weight suddenly or for unknown reasons, talk to your health care professional immediately. Unexplained weight loss may indicate a serious health condition. And even if it doesn't, simply being underweight is linked to menstrual irregularity, menstrual cessation (and sometimes, as a result, dental problems, such as erosion of the enamel and osteoporosis) and a higher risk of early death.
Although growing bodies need plenty of energy in the form of calories, many children and teenagers consume way too many, says Ruth Frechman, RD, a spokesperson for the American Dietetic Association. The latest findings from federal surveys show that 18% of adolescents and teenagers are fatter than they should be. Kids who are obese are 16 times more likely than healthy weight children to become obese as adults, other findings show.
However, 30% is still a lot of fat for one serving, so considered absolute values like how many grams of fat, carbohydrates, protein, etc. are consumed instead of relative values like "50% less fat." Additionally, reaching fitness goals is largely about calorie intake. More body fat and unwanted weight will be gained by eating 500 calories of a low-fat item than by eating 100 calories of a high-fat item, so keep this in mind.