Since my kids have been little I've tried to cue them into what their body is telling them. Since I worked in the field of Deaf Education for several years my kids learned ASL early and were able to communicate with me early. When they were filling their diaper with smelly gifts for me I cued them into what they were doing. When they had just peed I filled them in on that. As a result, I believe they potty trained early and even now at 2 1/2 my second superhero can alert me to where he has an owie (strep throat, flu, cold, headache, etc). They're more specific with their descriptions of things.
As we've continued on this food journey away from processed foods I've experimented a bit. When we visit the bank or doctor's office and are offered a lollipop I watch to see how they react. Then I cue them in if there is a very clear obvious reaction. My almost 5 year old has realized that he can't seem to finish the large lollipop without feeling sick to his stomach. My 2 1/2 year old literally runs in circles about 5 minutes after having anything with artificial food dyes in it.
I try not to be too strict with my kids. So I make healthier substitutes for foods so they don't feel like they're missing out.
My Handsome Hubby went out of town for a few days so I decided to test out our stomachs. Crazy I know but we had a sleepover party with all the "good" things. Gluten free pizza, Ruffles, chocolate chip cookies, and juice mixed with club soda. Keep in mind, we've been on a 90% grain free processed sugar free diet for 10 months now. No juice is in our house, pop just doesn't happen. My kids were crying and felt sick by bedtime. My almost 5 year old said, "I just don't feel good mom. Now I know why you don't want us to have junk food." Granted moderation is the key and I just let them eat until they felt they were full but I wanted them to realize how food affects how you feel. My experiment worked.
So now my challenge to you. I know I've said it before but I'm going to say it again. Start to change your family's eating habits now. You can do it gradually. Cut out pop week one. Cut out juice week two. Rid your house of drinking your calories. Cut out coffee creamers or make your own out of real cream, maple syrup, and vanilla. Cut out chips. Our bodies weren't made to eat the processed foods and when you eat them, you overeat them. Your brain says you need more when in actuality you don't. Eating whole foods fills you faster and keeps you satisfied longer. You'll eat fewer calories and get your family off the emotional roller coaster of carb mood highs and lows. Start small and keep moving forward. It's worth it but you have to keep trying to see the results.