Eating too few calories will help you lose weight, but can also make you sick. The number of calories you need depends on your height, weight, age and activity level. Your basal metabolic rate, or BMR, is the minimal amount of calories you need for body functions. To get a clear picture of her calorie needs, an active women should factor in her activity level. An active woman who eats 1,200 calories per day is likely not giving her body enough energy.
Your body uses calories for energy. An active woman who eats too few calories may depress her metabolism. (See References 4, pg 1) The minimum amount of calories a woman needs is 1,200. (See References 1) An active woman needs more calories to keep her metabolism functioning properly. Eating too few calories can cause health problems. Women who eat too few calories predispose themselves to vitamin deficiency, hair loss and abnormal menstrual cycles. (See References 2)
Basal Metabolic Rate
Consider your BMR when determining the minimum amount of calories to eat daily. Your basal metabolic rate equals the amount of calories your body uses while at rest. (See References 3, pg 54) Even when you do not engage in physical activity, your body uses calories. At rest the human body burns calories for circulation, hormone balance, digestion and respiration. (See References 3, pg 54) The BMR equation factors in your height, weight, age and gender. Use the following equation to calculate female basal metabolic rate:
BMR = 655 + (4.3 x weight in pounds) + (4.7 x height in inches) - (4.7 x age in years) (See References 3, pg 55)
Active women burn more calories than sedentary women. When you engage in physical activity, the amount of calories you need increases. The BMR equation does not account for physical activity. Active women need to eat more calories than their BMR. Multiply your BMR by the appropriate activity factor to determine your caloric needs. The value of the activity factor depends on your level of activity. Extremely active women have an activity factor of two. The activity factor for lightly active women is 1.375, moderately active women 1.55 and very active women 1.725. (See References 5, pg 2) For example, an extremely active woman with a BMR of 1,200 will need 2,400 calories per day.
For proper nutrition it is important to obtain calories from all three macronutrients: protein, fat and carbohydrates. Each gram of carbohydrates you consume gives you four calories. Protein also provides four calories per gram. Fat contains the most calories per gram at nine. (See References 6) The 2010 Dietary Guidelines for Americans recommends getting 45 percent to 65 percent of your calories from carbohydrates, 20 to 35 percent from protein and 10 to 35 percent from fat. (See References 7, pg 15)