Effect of Food
Average diets

In a recent poll, the majority of Americans over the age of 25 are overweight ¹.  According to a Harris Poll conducted this year, the percentage of Americans over the age of 25 that are obese (exceed the body mass index) has risen from 58 percent in 1983 to 80 percent in 2002.  These results were not unexpected, as the average American diet has changed to rely heavily on sugars and fat. This diet, along with a lack of exercise, are the reasons that experts say that heart disease is so prevalent in our society.

The actual composition of the average American diet is somewhat hard to figure out.  One method that has been used is to survey Americans about their eating, and then to tally the results.  This has been done several times in the past by the USDA, the most recent results of which date from 1994-1998.  In this latest survey, the data shows that the average male over the age of 20 consumes about 2450 calories a day, while the average female in the same age bracket consumes about 1650².  The problem with using this type of method for data acquisition is that people will under report how much food they consume on average, either because they change their diet during the survey period or because they "forget" certain calories they consume in an effort to not look like a large consumer.  

Another method for acquiring the data is to measure all of the food produced in the U.S., and to account for all food lost either to export, damage, or waste. When this is done, it is found that the average American adult consumes almost 3700 calories of food per day³. As you can see, this number is significantly greater than that which is measured through the surveying technique.  While neither value probably is what the average American consumes, each of these methods allows us to make comparisons that are valid.  For instance, the surveying method allows us to see the ratio of different foods, vitamins, and minerals that are consumed (ex. percent fat, percent protein, etc.).  The second technique allows us to make comparisons to the diets of other countries.  In China, for instance, the second method yields an average diet of about 2800 calories per day, which is considerably less that that for America.

The composition of our diet is also radically different from that of most of the world, which is also another reason for health concerns. Our diet depends much more on animal products than most other countries. This is seen by the amount of meat and milk that we consume in an average day. The table below compares the composition of our diet with that of the average Chinese diet. 

 

Average 1994-96 Data	Average USA Diet	Average Chinese Diet
Animal Products	1006	461
Grain (excluding alcohol)	851	1646
Vegetables and Other	1767	659
Total Calories	3624	2766

Source: FAOSTAT
 

Our diet also has repurcussions for the environment. These differences in composition and amount correspond to a large difference in the agricultural demands. The amount of calories means that more food must be produced, which means more land must be used. The higher amount of animal products also requires more land. Since cattle, pigs, chickens, etc. are higher on the food chain than plants, they require more space to produce one pound of food than is required by plants. These two differences mean that more land must be used to produce the food, which means that less land is left undisturbed.

The following websites will give you more information about food, nutrition, and agriculture.

Nutrition

Nutrient Data Lab (USDA)
Dietary Guidelines (Federal Consumer Information Center)
Recommended Daily Allowances (USDA)
Nutritional Diseases (eMedicine.com)
BMI

Food Supply Issues

Can China Feed Itself? (IIASA)
Food Safety (USDA)

After reading through these and any other sites that you might find, answer the following questions:

• Is your diet healthy? Does it fall within the dietary guidelines outlined by the federal government?
• Use the BMI link to calculate your body mass index.  Is the figure, and corresponding description (underweight, normal, overweight, obese), what you expected?
• In general, the amount of grain that can be grown on a piece of land is about ten times the amount of meat in weight that can be raised on the same amount of land. Since meat is about twice as dense in calories as grain, this means that the number of calories per acre of land is about 5 times more for grain than for meat.   Given this, is it realistic to expect a country like China to be able to adopt an average diet like the American diet?