Overweight teenagers

If you're a teenager who's overweight, you're certainly not alone. Nearly one in five UK children leave primary school obese.

What are the causes of being overweight?

Being overweight usually results from an "energy imbalance." In short, when you take in more calories than you burn, you gain weight.

Poor eating habits can help make teenagers overweight, particularly if they live on fast food and high-calorie processed food. Studies show that many teenagers eat more high-fat foods and fewer foods with necessary nutrients (vitamin A, folic acid, fibre, iron, calcium and zinc) than is recommended for optimal health.

Much of the time, being overweight stems from a combination of poor eating habits and a sedentary lifestyle. That means a lifestyle with too much time spent in front of the computer or TV screen and too little time being physically active.

Girls are particularly at risk of being overweight as they move through the teenage years - a time when they typically become less active.

Genetics also play a role in weight. If one or both of your parents are overweight or obese, the chances are greater that you will follow in their footsteps.

Sometimes, emotional distress can result in excess fat. Teenagers may make bad food choices when they are upset, depressed, or anxious and turn to biscuits, sweets, and crisps for comfort. Stress may also trigger eating binges.

Problems with your thyroid gland may result in weight gain, but this is not a common ailment in the teenage years. In addition, weight gain is one of the side effects of certain medications, like corticosteroids. These are sometimes used to treat asthma, allergies, and juvenile rheumatoid arthritis.

How is being overweight determined?

How much should you weigh? In the past, a height/weight chart was used. Today, most experts believe that body mass index ( BMI) gives a more accurate picture of health. BMI is defined as body weight in relation to height.

Teenagers with a higher percentage of body fat tend to have higher BMIs than teenagers who have a greater percentage of muscle. However, in a few cases - such as with very muscular athletes, who might have high BMIs even though they are quite fit - the BMI may not give an accurate picture of health risks.

And what's the difference between "overweight" and "obese"? "Overweight," defined as having a BMI of 25-29.9, implies being too heavy for one's height. Obesity, defined as having a BMI of 30 or above, refers specifically to having too much body fat. It is extra body fat, not muscle that increases the risk of serious health problems.

Can being overweight harm my health?

When your doctor says you are "overweight," you are at greater risk of serious problems, such as heart disease, high cholesterol, and high blood pressure. Overweight teenagers are also at higher risk of psychological problems, such as depression. Also, being overweight and having increased abdominal fat is closely linked to type 2 diabetes, which has increased dramatically in teenagers.

Being overweight is associated with early onset of sexual maturity in girls. But overweight boys may have delayed sexual maturity.