Both guilt and shame are not effective Behavior changers. In medical literature and psychology it is known that positive reinforcement is much more successful.
In medicine we speak of motivational interviewing, what we see is that when you tell patients the negative consequences of their behaviors they almost never change, meanwhile if you point to the positive consequences of behavior change they will often improve. For instance, I have many patients who tell me that the reason why they keep their diabetes under control, exercise reduce blood pressure, Etc is that they want to see their grandkids graduate from high school or college, Etc. In fact, even the examples I can think of where a negative consequence led someone to really change your behavior, when you talk to them they often identify that they're doing for positive reasons. For instance, I once showed a patient who was smoking how they were some changes as long x-ray, and he ended up quitting smoking on the spot, later he described that his main motivation was that he wanted to be around for his kids.
So, with the topic at hand, when you ask the question how do you get people to eat healthy and lose weight, beating them over the head with the consequences of that behavior does not work, it just makes you and them angry, and maybe depressed. Showing them potential benefits of more healthy eating is much more successful strategy, and also much more pleasant.
In fact, technically, it's not that you show them the positive benefits, you have to help them identify what they would appreciate about the healthier Behavior.