Listen, man, first of all, being an asshole is not something that should be celebrated and it is not a goal you should strive to achieve. By starting out with this tough love approach you may think that you are helping him, but in reality, you are just violating one of Cialdini's 7 principles of persuasion. You have decided to embrace unliking, oddly. And while tough love and public shaming do indeed work in a more collective society (like Japan) it does not work so well in an individualistic society like ours.
You pointed out that portion sizes have grown, and waistlines have expanded along with them. Someone pointed out the amount of sugar in carbonated beverages. Someone probably pointed out that other foods have been engineered to be as addictive as possible. Another pointed out that the difference between food addictions and other addictions is that food is a necessary component to sustain life. Sawbones linked an article that speaks to the constant battle that obese people face as biology is working against them. You already know that the advertising for food and in particular junky food is a near much more frequent than other vices. Heroin is not being advertised on some billboard outside your office or in your home late at night. Nor is it full of attractive people looking like they are having fun.
But comparisons are silly really. The fact that people have busier lives leads to more eating out. That parents taught their kids to 'clean their plate' in the past has an impact especially as portion sizes grew. That food is engineered to be more addictive has an impact. That the body is biologically wired to hoard calories has an impact. That we keep pushing people who are worn out to exercise willpower and then constantly bombard them with advertisements to undermine their willpower has an impact. Ultimately, it is lazy thinking to believe people suddenly and magically became lazy and stopped moving or caring rather than taking the time to look into the cause of such behavioral, lifestyle, and dietary changes at a population level.
We should be addressing this as a national problem, maybe sin taxing shitty food like we sin tax other vices. Maybe limit advertising and signs which promote shitty restaurant options or that try to hook kids with toys.
Blaming individuals without empowering them doesn't really work unless your goal is simply to be an asshole and cause people to doubt themselves. To me, this is a parallel to other societal problems that we have. For example, guns are the most likely cause of death for children (a societal problem) and yet we continue to try to push this as an individual problem. So the natural question to might be something like "Why are we so fucking bad at actually coming together to solve problems instead of just pointing fingers?" Wait, you told me, we are lazy.