Factors that Determine Daily Caloric Intake

There are many factors that determine the recommended daily caloric requirement for a teenager. One factor is activity level. The more active you are, the more calories you burn, so you therefore need to consume more calories. If you play a lot of sports or other activities, you need to consume more calories to maintain your energy levels. If you are sedentary, you hardly burn any calories, so you therefore need to consume less calories.

Another factor is body size and body shape. If you have a higher lean body mass (LBM), you have a higher basal metabolic rate (BMR). Lean body mass is your total body weight minus body fat weight, so LBM includes your bones, ligaments, tendons, internal organs, and muscles. Basal metabolic rate is the amount of energy (calories) that your body needs to function while resting for 24 hours. Heavier, taller people have a higher basal metabolic rate than lighter, shorter people. If you have a larger body mass, then you need to consume more calories in order to do normal bodily functions. The more muscles you have in your body, the more calories you burn at rest, so if you don't have as much muscle, you don't burn as many calories at rest.

 Average daily caloric needs based on gender, age, and activeness

A third factor is gender. Body compositions (the ratios of lean muscle, bone and fat) are different for males and females. Males usually have more muscle mass than females, so they often need more calories than females. Because of this, a female's basal metabolic rate is usually around 5% to 10% lower than a male's.

A fourth factor is age. Your metabolic rate usually slows down with age, meaning that the older you get, the less calories you need to consume. However, if you develop more muscle by properly exercising, weight training, and eating healthy while young, you can prevent your metabolic rate from slowing down. You could possibly even reverse the slow-down, making your daily caloric intake go up, rather than down.

On average, boys between the ages of 11 and 13 (pre-teens/early teens) need 1,800 to 2,600 calories per day, while boys ages 14 to 18 (middle/late teens) need around 2,200 to 3,200 calories per day. On average, girls between the ages of 11 and 13 (pre-teens/early teens) need 1,800 to 2,200 calories per day, while girls ages 14 to 18 (middle/late teens) need around 1,800 to 2,400 calories per day. Exact daily caloric needs depend on the other factors listed (see table above).


Citations:
http://dailyburn.com/life/health/how-to-calculate-bmr/
  "How to Calculate Your BMR (And Why It Matters)." Life by Daily Burn How to Calculate Your BMR And Why It Matters Comments. N.p., 31 Jan. 2015. Web. 22 Apr. 2016.
http://dailyfitnessresource.blogspot.com/2012/10/6-major-factors-affecting-your-calorie.html
  "Your Daily Dose of Fitness!" : 6 Major Factors Affecting Your Calorie Requirements. N.p., n.d. Web. 22 Apr. 2016.
http://healthyeating.sfgate.com/factors-contribute-many-calories-consume-2826.html
  "What Factors Contribute to How Many Calories to Consume?" Healthy Eating. N.p., n.d. Web. 22 Apr. 2016.
http://healthyeating.sfgate.com/many-calories-should-average-teenager-eat-per-day-3718.html
  "How Many Calories Should an Average Teenager Eat Per Day?" Healthy Eating. N.p., n.d. Web. 22 Apr. 2016.

http://lf2012springa12305.blogspot.com/2012/05/factors-of-caloric-intake.html

  "Factors of Caloric Intake." Factors of Caloric Intake. N.p., n.d. Web. 22 Apr. 2016.

http://www.livestrong.com/article/41003-definition-lean-body-mass/

  "The Definition of Lean Body Mass." LIVESTRONG.COM. LIVESTRONG.COM, 03 Mar. 2016. Web. 22 Apr. 2016.

Pictures:
http://www.interactive-biology.com/wp-content/uploads/2012/05/Low-calorie1.jpg
http://www.wisefoodstorage.com/blog/wp-content/uploads/2014/01/Screen-Shot-2014-01-22-at-2.36.13-PM-300x222.png