Is it normal that i throw away junk food?

I'm concerned, both for my parents and myself. I live at home (about to graduate high school), and I generally have a good relationship with my parents.
However, I'm beginning to have concerns about their health and our relationship. My parents aren't "fat", but they're both chubby, as is normal for parents in their late 50s. They're generally pretty good with what they eat (lean meats and steamed vegetables, mostly), but lately they've started buying more junk food like ice cream and chips. I'm starting to get concerned because they always seem to have a point during the week where they give in and dig into the junk food. I'm worried because now they're incorporating it into their everyday diet. I want them to be happy; I'm much more concerned with how they see themselves than how healthy they are. Yes, they have high blood pressure and the like, but they're getting old anyway and they're not obese or anything. I just want them to be happy with themselves. My mother especially tends to be really self-deprecating and calls herself fat, obese, etc. on a regular basis. I tell her she looks fine and really isn't fat compared to most people, but she won't believe me. I feel like she also uses food as a coping mechanism.
So, I've started throwing it away. Occasionally, I'll take ice cream and crackers and chips into my room so they think I'm eating them, only to take a couple bites and throw the rest in the trash. If they knew I was doing this, they'd be angry, not because I was depriving them but because they hate wasting food. But I have a hard time stopping, and I only want to help.
Is this normal? Is there any way I can address this issue with my parents effectively? Has anyone had a similar experience? Am I being controlling? I'm concerned.. Thank you, any replies are appreciated.
Tl; dr- my parents have been buying junk food when they're supposed to be on a diet, and I throw it away. Is it normal?