A woman’s energy requirements vary throughout the life cycle, including changes to her physical condition, such as pregnancy and lactation, disease states, need to gain or lose weight, level of physical activity and normal changes related to aging. Various formulas estimate the energy requirements of a woman based on these and other factors.
A woman needs to consume about the same number of calories she burns in her daily activities. An approximate total energy expenditure for a woman includes the amount of energy needed by her body when at rest plus the amount of energy needed for her level of physical activity plus the energy required to digest and metabolize food. Additional factors that may affect her needs include disease state, pregnancy and lactation.
Optimal health and energy requirements depend on balancing the number of calories consumed in food with the number of calories expended in work, play and normal body functions. Overeating can result in obesity, which is a risk factor for chronic diseases like diabetes and heart disease. Eating too little can mean creating a deficiency of certain nutrients that may also result in illness.
One pound equates to 3,500 calories. To lose 1 pound per week, a woman needs to either eat 500 fewer calories per day, burn 500 more calories per day or use a combination that equals a difference of 500 calories per day. For instance, she could reduce food intake by 250 calories and increase physical activity by 250 calories per day to lose 1 pound per week. A woman should not lose more than 2 or 2 1/2 pounds per week for safe weight loss.
During pregnancy, a woman’s metabolism increases by 25 percent. To support the optimal weight gain during pregnancy, a woman needs an additional 300 calories per day during the second and third trimesters. Breastfeeding costs about 850 calories per liter of milk. The RDA for breastfeeding adds 500 calories per day during lactation, according to “Nutrition Across the Life Span.”
As a woman ages, lean body mass declines, accompanied by a decrease in energy required for metabolism. Energy needs decline but nutrient requirements may increase. Diminished sense of taste and smell can contribute to loss of appetite and food intake, especially after age 70. Meeting all nutrient requirements on less than 1,500 calories per day can present a challenge.
The recommended dietary allowance for energy is based on a light to moderate activity level, according to the Food and Nutrition Board and reported in “Krause’s Food, Nutrition, & Diet Therapy.”
For example, a healthy woman 19 to 24-years-old, 5 feet 5 inches tall and weighing 128 pounds requires 2,200 calories per day. A healthy woman 25 to 50-years-old, 5 feet 4 inches tall and weighing 138 pounds also requires 2,200 calories per day. A healthy woman 51-years-old or older who is 5 feet 3 inches tall and weighs 143 pounds requires 1,900 calories per day. A dietitian can help calculate energy requirements personalized for an individual woman, including differences in body size, life stage, level of physical activity and energy required due to a disease state, trauma or injury.
- Nutrition Across the Life Span; Mary Kay Mitchell
- Krause’s Food, Nutrition, & Diet Therapy, 10th Edition: L. Kathleen Mahan and Sylvia Escott-Stump
- USDA: Dietary Guidelines for Americans 2005
- University of Maryland Medical Center: How Many Calories and Fat Grams Do You Need?
- Thomas Northcut/Photodisc/Getty Images
This article reflects the views of the writer and does not necessarily reflect the views of Jillian Michaels or JillianMichaels.com.