Evidence that obesity is influenced by factors in addition to genetics includes the fact that

A) mice injected with daily doses of leptin become less active and gain weight.
B) people lose a pound of weight for every reduction of 3500 calories in their diet.
C) the weights of adopted people are highly correlated with the weights of their adoptive parents.
D) the average adult American weighs over 20 pounds more today than 50 years ago.

The fact that the average adult American weighs over 20 pounds more today than 50 years ago suggests that environmental factors, such as changes in diet and physical activity levels, are contributing to the obesity epidemic. This supports the idea that obesity is influenced by factors beyond genetics. Choices A and C both suggest a genetic component to obesity (leptin is a hormone produced by fat cells and adopted people share genes with both their biological and adoptive parents), while choice B pertains to the concept of energy balance and does not necessarily support or refute the role of genetics in obesity.