Although many other factors are involved in weight loss, calories in versus calories out still matter. Calorie counting isn't required, but it's helpful to have an estimate of how many calories you need each day so you can more easily balance the calories you eat with the calories you burn.
According to ACE Fitness, three main factors affect your daily calorie needs: resting metabolic rate (RMR), activity level, and thermogenesis, or thermogenesis. RMR accounts for approximately 60-80% of your daily calorie needs. RMR is the amount of energy (calories) your body expends at rest. Physical activity level is the second most important factor in calorie needs, but it varies from person to person. A small portion of your daily calorie needs is thermogenesis, which is the energy used to digest food.
According to the Dietary Guidelines for Americans, estimated calorie needs are based on your age, gender and physical activity. Men generally need more calories than women, and active people need more calories than sedentary people. Calorie needs decline with age. For example, a moderately active man aged 31-35 needs about 2,600 calories per day, while a moderately active woman in the same age group needs 2,000 calories per day. An active 25-year-old man needs 3,000 calories per day, compared with 2,400 for a sedentary man of the same age. As we age, our calorie needs change. At age 19, a woman's intake should be between 2,000-2,400, depending on activity level; at age 61, her daily calorie needs have dropped to between 1,600 and 2,000.
