The term "phenotype" refers to the observable physical properties of an organism; these include the organism's appearance, development, and behavior. An organism's phenotype is determined by its genotype, which is the set of genes the organism carries, as well as by environmental influences upon these genes.
No, obesity is caused by lifestyle and choices that individuals have to decide for themselves. You shouldn't need laws because it's a person's choice whether they chose to exercise or control their eating.