Calorie Needs during Pregnancy
Along with is nutrient composition, every food also has a calorie value. The calorie is a way to measure the amount of energy in a food. A food with 400 calories stores more energy than a food with 200 calories.
During a 24 hour period, your body uses between 1500 and 2500 calories of energy to live. Your body will also use about 300 additional calories to maintain a healthy pregnancy. Activities such as digestion, growth, physical movement, thinking and breathing all use the energy you get from food.
When your body doesn't get enough calories, it has to break down body tissues to retrieve the stored energy. Ideally this breakdown will come from fat stores, but much of it will also come from muscle because your body is not strictly interested in the minimum calorie level. In addition to energy, your body needs proteins to build and repair tissues and build all the tissues, organs and muscles of your developing baby.
Your body does not have a storage system for protein, any excess protein is broken down and stored as fat. Once the protein is stored as fat it cannot be made into a protein again. Since your body is building your baby every day of your pregnancy, your protein needs are high. If you are not eating enough food on a daily basis to provide energy and protein for you and your baby, your body will begin to break down tissues (usually muscle) to get the nutrition you need. At the end of your pregnancy, your body will be less tone with less muscle to support the increased levels of fat and much more difficult to get into your pre-pregnancy shape.
The answer is not to eat excessive amounts of food. When you eat too much food, your body stores the excess as fat. You don't have to eat fatty foods to gain weight, but it doesn't help maintain a healthy weight. Fatty foods tend to be high in calories, and extra calories of any type will be stored as fat. Your body stores extra food as fat because it is the easiest way to store the most energy. If you eat too much food on a regular basis during your pregnancy your body will store the extra as fat. This storage will happen more efficiently than before pregnancy because your higher estrogen levels during pregnancy increase the rate at which fat can be stored.
Your best bet is to eat the right amount of calories. There are some formulas you can use to get an idea of how many calories your body needs per day, however you don't need to be that precise. Not only will your calorie needs vary from day to day based on your activities, most calculations are only based on height and weight instead of body composition. Instead, pay attention to your body. When you are hungry eat something and when you are satisfied (not full) stop. You will probably find you eat several small meals or large snacks a day this way, and that could be beneficial due to the metabolic changes during pregnancy.