5 common Causes of excess Weight gain in teens

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Growing teens tend to gain weight gradually. It is necessary to have a healthy increase in weight but excess accumulation of calories could be worrisome. A sudden gain in their weight also may not be normal.

A poor diet and an inactive lifestyle are the most common reasons for excessive weight gain in teens. Sometimes, it could be hormonal changes during puberty, and in a few cases, an underlying medical condition.

While it is necessary to control excessive weight gain in teens, they should not starve themselves to restrict the normal weight gain that is required for their healthy development.

In this MomJunction post, we tell you the ideal weight gain in teenagers, the top five reasons for excess weight gain and what they should do to maintain a healthy weight. 

What Should Be the Ideal Weight of Teens? 

To determine the ideal weight of the teen, you need to consider several factors besides their age.

  • The US Center for Disease Control and Prevention (CDC) and the American Academy of Pediatrics recommend the use of BMI calculator to determine if a teen has normal weight, is overweight or obese (1).
  • The BMI calculator considers the height and age of the teenager in determining their weight threshold.
  • BMI for teens is interpreted differently, which is why you should refer to a BMI chart, such as the one developed by the CDC, standardized for children.
  • The CDC says, “Because there are changes in weight and height with age, as well as their relation to body fatness, BMI levels among children and teens need to be expressed relative to other children of the same sex and age (2).” Therefore, the weight of a teen is evaluated in comparison to other teens and is assigned as a percentile.
  • The minimum is the 5th percentile, and the highest is the 95th percentile. When the teen’s BMI is equal to or greater than the 95th percentile, they are considered obese since it means the teen’s weight is greater than 95% of teens.

Ultimately, the teen’s BMI score on the percentile chart will determine if they are of a healthy weight or not.

[ Read: Diet For Teenage Girls ]

BMI Percentile Table and Weight Status 

Percentile RangeWeight Status
Less than the 5th percentileUnderweight
5th percentile to less than the 85th percentileNormal or healthy weight
85th to less than the 95th percentileOverweight
Equal to or greater than the 95th percentileObese

Source: US Centers for Disease Control and Prevention 

BMI Calculation and CDC Charts 

You can calculate the BMI of the teen using the following formula:

  • Weight (kg)/ (Height in meters x Height in meters)
  • (Weight (lb) x 703)/ (Height in inches x Height in inches)

Round off the number to one decimal place. For example, 22.554 becomes 22.5.

You can calculate the BMI of your child and plot it on the chart right at home:

CDC BMI Chart For Boys

CDC BMI Chart For Girls

What Causes Excess Weight Gain In Teens?

Here are a few reasons that contribute to excess weight gain in teenagers (3).

1. Eating unhealthy food

  • Unhealthy snacking between meals can accumulate excess calories that cause weight gain. This is particularly common when teens feel “bored” and go every now and then to the kitchen or the refrigerator looking for food that makes them feel better.
  • Teens are likely to gain weight if they eat high-calorie, low-nutrient fast food even if they have a nutritious diet at home.
  • Access to junk food combined with the freedom that their pocket money gives them can also result in building unhealthy eating habits. Regular binge eating of fast foods and processed foods can lead to weight gain.

2. Insufficient physical activity 

  • The teenager needs to get adequate exercise to stay in good health. When a teen has no physical activity, then they invariably gain weight.
  • Children who do not eat junk food may also be at risk of putting on over weight if they do not exercise at all.
  • Teenagers burn fewer calories when at rest, according to a study (4). The study noticed that 15-year-olds burn 400 to 500 fewer calories per day when at rest, compared to what they did at the age of ten years.

3. Puberty

  • Puberty alone may not cause significant weight gain. However, the growth spurt tends to cause increased hunger, which may accelerate weight gain in teens who eat in excess and do not get enough physical activity.
  • Children in their early teens (13 to 14-year-olds) are likely to gain weight naturally as a result of hormonal changes during puberty. Weight gain may be more prominent among girls (5).
  • The child may gain about 6.5 pounds (3 kilograms) in a year after puberty (6).

[ Read: Weight Loss In Teens ]

4. Psychological reasons 

  • The changes in the body make adolescents highly self-conscious and sensitive to their figure. They may unnecessarily compare themselves to their peers and be under pressure of having the “ideal body” (7). The dissatisfaction of not having the perfect body may lead to depression, which in turn could lead to unhealthy eating habits, and thus weight gain (8).
  • Several teens have a flawed opinion that they are fat even when they are not. In the long run, this could lead to reinforcement of the belief. Some experts state that a teenager’s constant belief that they are fat can lead them to gain excess weight (9).
  • Stress is also linked to weight gain. Research suggests that stress and depression can lead to higher consumption of sugary and fat-rich foods (10). Food is quite likely to work as a coping mechanism to alleviate the feelings of depression and chronic stress.

5. Health reasons

  • Hypothyroidism is a condition where the thyroid gland becomes underactive and produces lesser thyroid hormone, one of the symptoms is an increase in weight (11). The teenager is also likely to feel tired and fatigued most of the time. This is most common in girls, particularly if some other woman in the family has thyroid disease.
  • Cushing’s syndrome is a rare medical condition that causes the body to produce an excess of cortisol, which is the stress hormone produced by the adrenal glands (a gland that lies over each kidney). One of the significant symptoms of the condition is weight gain. Accumulation of fat around the base of the neck is another symptom. Children with Cushing’s syndrome tend to become obese and also grow slowly (12).
  • Certain medicines can also lead to excess weight gain due to the compounds in them. Sometimes, medications can cause complications that in turn, lead to weight gain. An example is glucocorticoids, which is a type of steroid hormone commonly used in the treatment of immune system disorders like asthma and lupus. Long-term use of glucocorticoid can cause Cushing’s syndrome, which in turn leads to weight gain.

Excessive weight gain can be controlled through changes in lifestyle and diet. But if that doesn’t help, you may have to consult a medical professional.

When To Be Concerned About Weight Gain? 

Consult a doctor about your teen’s weight gain if:

  • The child has extreme weight gain beyond 16 years of age and even towards the end of the teen years (2) (4).
  • You sense the teen is gaining weight due to binge eating, which itself may have been caused by constant peer pressure, body image issues, or some other matter that is stressing them out.
  • The weight gain seems to have begun after the kid was prescribed medicine. In such a case, talk to the doctor about it.
  • The body develops abnormally high deposits of fat around the neck, face, and the abdomen. The skin on the abdomen has reddish-pink stretch marks (these are the symptoms of Cushing’s syndrome).
  • The child also appears tired, dull and complains of muscle aches.

As a parent, you may be able to see that something is off with the child’s weight, behavior, and eating habits. Being observant of the changes and keeping track of the child’s weight, and overall health can help you deal with it better.

[ Read: How Can Teens Gain Weight? ]

If you are alert to any sudden or abnormal changes and act immediately, weight gain can be controlled sooner. If you are unable to help your teen manage weight better, then seek a medical opinion and a nutritionist’s help to address the real reason for weight gain. At all times, be aware of the teen’s correct BMI and look for any changes in their eating patterns and intervene in time to prevent excess weight gain.


1. Age-based Pediatric Growth Reference Charts; Baylor College of Medicine
2. About Child & Teen BMI; Centers for Diseases Control and Prevention
3. Weight Management and Adolescents; Children’s Hospital Philadelphia
4. Teenage weight gain down to dramatic drop in calories they burn; University of Exeter/Science Daily
5. Stages of puberty: what happens to boys and girls; NHS UK
6. Physical Changes During Puberty; American Academy of Pediatrics
7. Adolescent development; U.S. National Library of Medicine
8. Felton et al., The relation of weight change to depressive symptoms in adolescence; National Center for Biotechnology Information
9. Can thinking that you are fat make you fat?; Norwegian University of Science and Technology
10. M Mooreville et al., Depressive Symptoms and Observed Eating in Youth; National Center for Biotechnology Information
11. Underactive thyroid (hypothyroidism); NHS UK
12. Cushing’s Syndrome; U.S. Department of Health and Human Services Follow us: Twitter Facebook YouTube

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