Final Answer:
Lack of exercise is an example of a(n) environmental risk factor for obesity and diabetes.
Step-by-step explanation:
Insufficient physical activity serves as an environmental risk factor for conditions like obesity and diabetes. This is because physical inactivity can raise a person's risk of developing type 2 diabetes and is associated with increased insulin resistance and poorer glycemic control independent of body weight.
Additionally, structured interventions combining physical activity and modest weight loss have been shown to lower the risk of type 2 diabetes in high-risk populations. Therefore, lack of exercise is considered an environmental risk factor for obesity and diabetes.