Your body weight depends on a simple equation: Weight change equals calories in minus calories out. Burn as many calories as you take in and your weight will remain the same. Factors such as genetics, metabolism and behavior make it difficult to accurately predict a person's calorie requirements, but simple formulas can provide useful estimates.
Your caloric requirement is proportionate to both body weight and activity level. The more you weigh, and the more active you are, the more calories you will need to maintain your weight.
Sedentary adults require about 30 calories per kg per day to maintain body weight; moderately active adults require 35 and very active adults require 40. One pound equals roughly 2.2 kg.
A 190-pound adult is 86.5 kg. If he is sedentary, 86.5 x 30 = 2,595 calories. Moderately active: 3,028 calories. Very active: 3,460 calories. So depending on activity level, someone weighing 190 pounds needs between 2,600 and 3,500 calories to maintain his body weight.
Maintaining a normal body weight is important for health. The body mass index, or BMI, gives a measure of relative weight, adjusted for height. A healthy range for the BMI is between 19.5 and 25.0.