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Weight Loss Health Guide

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Causes and risks for obesity


Many people with obesity who lose large amounts of weight and gain it back often think it is their fault. They may blame themselves for not having the willpower to keep the weight off, and many regain more than they lost.

Today, we know that biology is the reason some people cannot keep this weight off. Even among people who live in the same environment and eat the same foods, some become obese and others do not. Our bodies have a complex system to help keep our weight at a healthy level. In some people, this system may not be working normally.

Your body's gas gauge

Think about the gas gauge in your car. If your gas tank is full but your car’s gas gauge is broken, it may read empty. You would want to put in more gas, even when the tank is already full.

If you are someone who struggles to maintain a healthy weight, the reason may be that one or more of the signals that tells your brain when you have eaten enough does not work normally. In other words, your tank (stomach) may be full, but your brain (gas gauge) does not realize that.


What is different about people who have trouble losing weight, or who or lose and then regain the weight, compared to people who are thin or lose weight easily and keep it off?

Our bodies are set to keep our weight within a certain range. That weight range is at least partly determined by our genetic makeup. Genetic makeup refers to certain traits that we inherit from our parents. If you have the genetic makeup for obesity and you eat a lot of high-calorie foods and do not exercise, it is almost certain you will develop obesity. It will likely be harder for you to stay at a healthy weight than someone who does not have the genes for obesity.

Obesity is not caused by just one gene. There are hundreds of genes that influence body weight. People may have more genetic risk factors for obesity than others.

Learned behaviors and habits

The way we eat when we are children may strongly affect our eating behaviors as adults. When we repeat these behaviors over many years, they become habits. They affect what we eat, when we eat, and how much we eat.

Children are very good at listening to their body’s signals of hunger and fullness. They will stop eating as soon as their body tells them they have had enough. However, at some point a well-meaning parent may tell them they have to finish everything on their plate. This forces them to ignore their fullness and to eat everything that is served to them.

As adults, these same people may say that they feel guilty if they do not eat everything on their plate. And today, portion sizes are so large that eating everything on your plate may mean you are eating too many calories.

Other learned behaviors include using food to:

  • Reward good behaviors
  • Seek comfort when feeling sad or stressed
  • Express love

These learned habits lead to eating no matter if someone is hungry or full. Many people have a very hard time breaking these habits.

The foods we eat when we are children may influence our food likes and dislikes for life. Being raised on foods that are processed and high in fat, salt, and sugar may make it difficult to start eating natural foods, such as fruits, vegetables, and whole grains, when we become adults. Not knowing how to prepare these foods can also keep people from eating them.

The environment in which we live

We are surrounded by many things that make it easy to overeat and hard to stay active.

Many people have insufficient time to plan and prepare healthy meals. Some reasons are:

  • Families with more than one adult who works
  • Working longer hours
  • Having longer commutes

Less free time also means less time to exercise. Also, more people today work desk jobs compared to jobs in the past that had activity built in to them.

Devices such as remote controls, mobile telephones, escalators, elevators, and computers all make life easier for us. But fewer trips up and down stairs and fewer walks down the hall at work to talk with a co-worker mean that we are storing more calories instead of burning them off. The average American eats 100 - 200 more calories a day more than they did 10 years ago. This can lead to a weight gain of 12 - 25 pounds every year.

Many things have changed how and what we eat. Some of these are:

  • Children see up to 10,000 food commercials every year. Most of these are for candy, fast food, soft drinks, and sugared cereals.
  • More foods today are processed and high in fat.
  • Vending machines and convenience stores make it easy to get a quick snack, but they rarely sell healthy foods.
  • More people eat out, most often at food courts, fast-food restaurants, and all-you-can-eat buffets.

Other causes of obesity

Sometimes, medical problems or treatments cause weight gain. Some of these are:

  • Underactive thyroid (hypothyroidism)
  • Medicines such as birth control pills, antidepressants, and antipsychotics

Other things that can cause us to gain weight are:

  • Quitting smoking -- most people who quit smoking gain 4 - 10 pounds in the first 6 months after quitting. Some gain as much as 25 - 30 pounds.
  • Stress, anxiety, feeling sad, or not sleeping well
  • For women:
    • Menopause -- women may gain 12 - 15 pounds during menopause.
    • Not losing weight gained during pregnancy.
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Review Date: 10/19/2010

Reviewed By: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

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