The U.S. obesity rate has increased rapidly over the last several decades because of changes in Americans’ diets and patterns of physical activity. Obesity increases risk of cardiovascular disease, type 2 diabetes, and other serious health problems.
Researchers supported by the Population Dynamics Branch examined the rates of change in height, weight, and body mass index (BMI) from 1959 to 2008, using data from national health surveys. Their goal was to understand the magnitude of the changes we have experienced in body size and to put these changes into context. Their study was the first to use a metric called a “Haldane” to measure observed changes in human health. The haldane was developed by evolutionary biologists to study how much species’ traits change over each generation.
The researchers found that (PMID: 23220719):
- Americans’ heights increased most rapidly between 1960 and 1980, especially among higher income blacks, but the most rapid weight gains took place from 1980 onward.
- The highest rates of change in BMI have occurred since 1990, especially for middle-income Americans.
- The researchers also compared the haldane values they calculated to those computed by evolutionary biologists who studied other species in the wild. They found that the rates of change in these three human characteristics were similar to the fast pace of change observed in other species that have lived through a rapid, human-driven change in their ecosystem.