When my client (at 62 year old man) began a great work out program and became obsessed with getting healthy. His neighbors told him he was being "controlled"--that he needed to seek therapy to go over his recent focus on health. Their fear was that he was brainwashed into a work-out program .
As a hypnotherapist and human being, I understand that we hang on to our present situations (even painful ones) but I am amazed at how hard we try to get others to hang on with us. Over 60% of the population is overweight, so it shouldn't be a surprise that when you go against the norm-you will encounter resistance from your co-workers and friends.
Remember that as you get healthier and slimmer, you may be a constant reminder of the choices your "out of shape" friends are not making. My advice: do NOT do what overweight people are doing. Choose what the healthy people are doing. Keep your focus on being healthy. The rest will follow.