The brain link: researchers have discovered an amazing connection between how the brain is involved in obesity and drug addiction
Science World, May 9, 2005
Continued from page 1.
Dr. Wang also notes that animal studies have revealed that group interactions can increase D2 receptor levels.
So, exercising and spending time with family and friends can help you keep your mind and body healthy--and help you avoid developing addictive behaviors.
That's all good to know. But according to Dr. Wang, perhaps the most important way the research can help is by giving people an understanding of their own behavior. It helps remove the mystery and stigma that surround addictive behaviors. "When you know the reason why," says Dr. Wang, "it makes everything much easier."
How Do You Design an Experiment?
By using their knowledge of addiction and how the brain works, Dr. Volkow and her colleagues had an idea: Maybe obese people have low numbers of D2 dopamine receptors in their brains--just like drug addicts. How did the researchers test their theory? They used the scientific method. The scientific method--which scientists in all disciplines have followed for hundreds of years--has four steps.
1. OBSERVE Researchers observed that D2 receptor levels are lower than normal in many drug abusers.
2. QUESTION Researchers raised the question of whether obese people, whose behavior can be described as "addictive," might also have low D2 levels.
3. PREDICT Researchers came up with a hypothesis: People suffering from obesity will have lower D2 levels than people whose weight is normal.
4. TEST Researchers took PET scans of obese adults to see how many D2 receptors they had.
The researchers validated the experiment by testing a control group--a similarly made up group of non-obese people. Accurate results from the obese group are only obtainable by looking at the results from the control group. The researchers also made sure the experiment was quantitative. In other words, they made exact measurements. (It wouldn't have been enough to say, "There were oodles of D2 receptors in that thin woman's brain.") Finally, the experiment was valid because it was set up in a way that was replicable--it could be repeated and tested by other scientists.
Wake-Up Call How Much is Too Much?
What's the difference between being overweight and "just a bit chunky"? The Centers for Disease Control and Prevention has very strict definitions of weight-related terms. They're net based on hew a person looks in jeans, they're calculated using height, weight, and--for people under 21--age and gender.
If you're worried that you have a weight problem, you should talk to a health professional. He or she will likely determine your body mass index (BMI) using this formula:
BMI = (Weight in Pounds) / ((Height in Inches) x (Height in Inches)) x 703
With your BMI and a specially made chart, the health professional can determine what percentile your BMI falls into. The percentile shows how your BMI compares with that of other teens of the same gender and age.
* BMI value at or above the 95th percentile is considered overweight.
* BMI value between the 85th and 95th percentiles is considered at risk for becoming overweight.
* BMI value between the 6th and 84th percentiles is considered healthy.
* BMI value below the 6th percentile is considered underweight.
As you may have noticed, there is no "obese" category for teens. That's because, unlike adults, young people's bodies are growing and changing. Once you reach adulthood, your body levels off. But teens who are overweight not only face health problems, they are also at higher risk for becoming obese as adults.
As BMI increases in adults, so does risk of the following:
* premature death
* cardiovascular disease
* certain cancers
If it turns out that you de have a weight problem, you and your parents can talk with your health professional about what actions you can take to improve your health.
Facts for Real Life
Q. Why is the number of overweight teens growing so rapidly?
A. Nobody knows for sure. It could be that today's teens are less physically active than those a generation ago. It may be that people are eating bigger portions of food than ever before. Dr. Volkow thinks one factor is the increasing ease with which people can get food today. Researchers are finding that there's a region of the brain--called the dorsal striatum--that is programmed to draw people to food even when they're not hungry. "This system was once very important for survival," says Dr. Volkow. "It was important to want food whenever you could get it, because you never knew when it was going to be around." In the contemporary United States, though, where there are fast-food outlets and convenience stores on every corner, "the system doesn't serve any purpose anymore," says Dr. Volkow. Now, with food so easy to get, people who follow their brains' instructions to eat, eat, eat are not staving off starvation--they're growing overweight.
Lesson 1: Obesity and Drug Addiction--What Do You Know?
OBJECTIVE To give students information about the connection between drug addiction and obesity; to increase students' understanding of addiction and the brain; to broaden students' understanding of the scientific process; and to assess students' knowledge of the topics before and after reading the article
NATIONAL SCIENCE EDUCATION STANDARDS
Life Science; Technology; Science in Personal and Social Perspective
WHAT YOU WILL DO
* Before beginning the lesson, hold a class discussion based on these questions: "Are there more teens who have weight problems now than in the past?" "How big of a problem is obesity?" "Could there be a connection between obesity and drug addiction?"
* Tell students that they are going to find out how much they know about food addiction and its connection to drug abuse. Distribute copies of Student Activity Reproducible 1. Tell students to write their names on the paper and label it No. 1. Then have them answer the questions. Collect and grade the papers.
* Have students read the article, "Obesity and Drug Addiction: The Brain Link." Next, hold a discussion based on these questions: "What is the connection between obesity and drug addiction?" "How can this connection help scientists understand how to treat and prevent both conditions?"
* Next, tell students it's time to find out how much they've learned. Give them a second copy of Student Activity Reproducible 1. Tell them to write their names on the paper and label it No. 2. When students have finished, collect the papers, score them, and record your data in the Assessment Guide below.
* Wrap up the lesson by discussing the "chicken-and-egg" question from the article: "What comes first, obesity or drug addiction, or a low level of D2 receptors in the brain?"
ANSWERS TO QUIZ QUESTIONS:
1. d; 2. c; 3. c; 4. b; 5. d; 6. b; 7. c; 8. c; 9. d; 10. a.
Lesson 2: Dangerous Cravings and the Brain
OBJECTIVE Students use scientific data to draw conclusions about the effect of increasing D2 dopamine receptor levels in the brain.
NATIONAL SCIENCE EDUCATION STANDARDS
Science as Inquiry; Science in Personal and Social Perspective
WHAT YOU WILL DO?
* Tell students that scientists know that D2 receptor levels are lower in people who suffer from obesity or drug or alcohol addiction. Ask students why they believe this is so.
* Explain that students will read about an experiment in which alcohol-addicted and non-alcohol-addicted rats were medically altered to increase D2 receptor levels in their brains. The researchers compared the alcohol intake of the rats before and after the treatment. Ask students: "If increasing the D2 receptors causes the alcohol-addicted rats to stop drinking, what might be the implications for humans?"
* Distribute Student Activity Reproducible 2. Have students complete it.
* Wrap up the lesson by asking students to speculate on how this experiment and others like it might lead to useful treatments for addiction.
ANSWERS TO REPRODUCIBLE:
1. Yes, the increase in DE receptors led to a drop in alcohol consumption. 2. Alcohol consumption fell in both groups, but the percentage drop was larger among the alcohol-addicted rats. In the non-alcohol-preferring rats, the D2 increase almost totally abolished alcohol consumption. In the rats that preferred alcohol, it reduced alcohol consumption to the level normally seen in non-alcohol-preferring rats. 3. This was done as a control to show that it wasn't the pressure of the needle itself but the D2 receptor gene causing the change in consumption.
Obesity and Drug Addiction--What Do You Know?
Test your knowledge of obesity, drug addiction, and the possible connection between the two by taking this quiz. Circle the correct answer to each question.
1. Between 1980 and 2002, the proportion of overweight teens in the United States
a. didn't change.