The foods you eat contain a certain amount of calories -- units of energy your body draws for fuel. Your body needs calories not only for physical activity, but also to carry out its various functions such as digestion and breathing. Calorie needs differ depending on various factors, with age being an important one as a naturally slowing metabolism will lead to weight gain faster. You need to consider other factors also, such as your activity level and whether or not you have certain conditions that might influence energy needs or metabolism, such as hypothyroidism. If you have questions about proper nutrition, consult your physician or a nutrition professional like a registered dietitian for guidance in designing a proper eating plan suited to your individual circumstances.
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USDA Minimum Calorie Recommendations
Regardless of physical activity level, your body requires a minimum number of calories to support your organs, tissues and the various tasks they perform. The U.S. Department of Agriculture has established recommended minimum daily calorie intakes for those who live a sedentary lifestyle, which means you typically do not exert yourself beyond the requirements of day-to-day living. Based on these guidelines, a 35-year-old woman should consume only about 1,800 calories daily, about 200 less than when you were in your teens and twenties.
Modifications for Physical Activity
If you live a physically active lifestyle, your body needs more calories to both fuel physical activity and replenish energy stores. A more active body will burn more calories even at rest. The USDA's recommendations for increased calorie needs are based upon whether you are moderately active, which equates to walking 1.5 to 3 miles daily or active, which equals walking more than 3 miles a day. Moderately active 35 year olds require about 2,000 calories a day while active ones need about 2,200 daily.
Because your metabolism continues to slow as you age, how old you are is an important consideration for how much you should eat daily. Not all calorie recommendations take age into account, however, and some rely on other factors. Physician Nadya Swedan, author of "The Active Woman's Health and Fitness Handbook," offers a formula to figure out daily calorie needs based on weight and activity level. Multiply your weight by 13 if you do about 20 to 30 minutes of aerobic activity daily, by 16 for 45 to 60 minutes, 19 for 75 to 90 minutes and 22 if you work out more than two hours a day.
In addition to consuming the right amount of calories for your needs, you also want to make sure you consume the proper proportion of fats, carbohydrates and proteins. Swedan recommends that women's diets comprise 50 to 60 percent carbohydrates, 20 to 30 percent protein and 20 to 30 percent fats.