Can an employer force one to take a physical to be able to receive insurance?

I would think that would protect both the employer and their insurance company. Take the example, that people could enroll with a physical or family history and then discover Diabetes or other health issues like cancer. An example of how high risk employees effect an employer our county had 20 ppl this past year with serious health issues which resulted in an additional $2M in expenses. The results are layoffs, increasing premiums, etc. all of which help keep the lid on our economy. If your resistance is based on a religious belief there may be some grounds for refusal, but I'm not an attorney or lawyer.