IB Evaluating BMI & Lipids

Lipids make up an important part of the human diet as they are energy dense molecules.  It is actually essential to have a percentage of body weight be composed of fat for both men and women, approximately 14-24% in men and 21-31% in women[1].  Moving below or above can be dangerous to one’s health.  One of the most often discussed national topics in the media is the problems of obesity in America.  Obesity can be measured by a formula called body mass index that uses an individual's mass in kilograms and height in meters or by a nomogram, used by connecting the weight and height graphs with a straight edge; the point at which the straight edge crosses the BMI table is the BMI value.  Calculated values can be compared to the following chart to determine whether a person’s body mass is at a healthy level.

In this activity, you will calculate your own BMI, compare it (anonymously) it to other members of the class and evaluate some of the scientific evidence for the threats of excessive consumption of trans fats and saturated fatty acids.

Objectives

• Application: Scientific evidence for the health risks of trans fats and saturated fatty acids.
• Application: Evaluation of evidence and the methods used to obtain the evidence for health claims made about lipids.
• Skill: Determination of body mass index by calculation or use of nomogram.

Part A: Calculation of BMI (completed individually)

Directions:

1. Determine your weight and height using the scale and rulers in the classroom.
2. Calculate your BMI using the nomogram chart.
3. Compare your BMI from the nomogram chart to the value obtained from the National Heart, Lung, & Blood Institute.
4. Turn in your BMI data to this form.
5. Using the BMI summarized data from this spreadsheet, create a 100% Stacked Column Graph in Excel or Google Sheets (see below).  The x-axis labels should be the number of days active per week with four series per day (the four BMI levels).  As there is not an average, no error bar or further statistical calculations are necessary.   Save your graph as an image and upload/insert it here (click here for instructions for how to do this).

Insert graph image here

Part B: Evaluation of Evidence (completed in your table group)

Numerous studies have been conducted to evaluate the connection of health risks (coronary heart disease) and fats, particularly trans and saturated fats.  Some studies suggest a positive correlation between consumption of these fats and CHD while others do not.

The most effective means of evaluating evidence on any scientific topic is to examine scientific journals.  However, these are often difficult to read and thus take practice to improve comprehension.

IB defines an evaluation as an assessment of implications and limitations.  To evaluate your research article, use the following definitions:

• Implications: Do the results of the research support the health claim strongly, moderately, or not at all?
• Limitations: Were the research methods used rigorous or are there uncertainty about the conclusions due to weakness in the methods?

Directions:

1. Examine the Purdue University’s How to Read a Scientific Paper for some helpful suggestions to reading scientific journals.
2. Open and use Google Scholar; Google Scholar is a way to search for primary literature source.
1. Potential Journal Articles:
1. Find a primary literature source that examines the effect of either trans fats or saturated fatty acids on coronary heart disease (CHD).  Your source needs to be a published study from a scientific journal.
2. Use EasyBib to create an MLA citation for your selected article; write it below.

As a table group, read the selected article in sections, discuss and answer the questions pertaining to each section.

1. Abstract: What do the authors conclude?

1. Introduction: Why did the authors do this study?

1. Methods:
1. How did the authors do this study?

1. How large was the sample size?  (It is usually necessary to have thousands of people to receive reliable results).

1. How even was the sample in sex, age, state of health and lifestyle?  (The more even the sample, the less other factors can affect the results).

1. Results:
1. What data/results emerged from the study?

1. Is there a correlation (positive or negative) between the intake of the lipid being investigated and the rate of the disease or health benefit?

1. How certain or uncertain is the data, how widely spread is the data? (This can be determined by the spread of data points on a scatter graph or the size of error bars on a bar chart.  The more widely spread the data, the less likely it is that mean differences are significant).

1. Conclusion/Evaluation:
1. What is the significance of these findings?