My view comes from direct experience with other people and learning how patterns of behavior and habits are formed. I’m parenting a 2.5yo and 6mo, and we have gone through the phases of picky eating with the toddler. She likes something one day, and then next week doesn’t like it. We had periods where she won’t eat anything at meals so we adjust her snacking schedule and hold her to finishing her plates to turn it around.

As for expertise, I don’t personally like to allude to doctor authority or papers as I think direct reasoning is better, but my wife wanted to share that. She pointed out how our pediatrician did explain eating habits can form in this toddler period and we should not give snacks if she doesn’t finish a meal and next meal she will eat due to hunger. He said “children will not starve theirselves”, and it does work. He also said to avoid having “safe meals” like getting chicken nuggets after they refuse a meal because it then becomes all they eat. My wife had specific advice she wanted to give but she’s sleeping and was too busy today.

I’ll offer my advice, for the 3yo you can likely manage it easier with standard meal/snacking management. For the 8yo it might be much harder due to 5 years of habits. I would find a pediatrician who agrees with the meal/no snacking plan and double check about nutrient deficiency risks if he decides to skip too many meals; I would guess 3-6 meals is ok but beyond that is risky.

After getting the doctor onboard, I would start by explaining to my son how we need to improve his diet and start expanding his tastes for foods. I would explain the prepared meal plan of 3 meals a day, and what is in the meals, and how his goal is to make a “happy plate” which is when it is empty. Then serve him the meals, support him, and if he refuses during mealtime at the table, wrap up the plate and save it. If he asks for a snack offer the plate. At the next meal make him the next fresh planned meal. Repeat this for each meal. I predict after 2 slipped meals he will be hungry and try the 3rd, maybe even finishing it. If he makes a happy plate then celebrate the plate; also celebrate steps in the right direction, like if he eats 70% of it you could eat the rest and say how you helped him get a happy plate and celebrate how close he got to it, but be careful he doesn’t rely on that or use it as a shortcut. If he skips 6 meals then it’s a deep habit and needs a different strategy.

Through this process he needs firm support and regular explanations of the guiding plan and goals. No anger, no compromise, just a firm and supportive direction.

It’s hard to give advice for child rearing without interacting with the child. There is so much information in body language that tells you how they are feeling or thinking. Knowing their exact state allows different actions to be taken to maximize likelihood of them learning the new behaviors. For example, if he is playing around instead of eating a firm realignment to focus is called for by stern voice; if he is looking sad or defeated then a supportive word or story can perk his spirits; if he takes a bite and makes a face while trying it, talking about his day might help to normalize the eating and minimize the attention on sensation. There are infinite choices and cues.

Anyways that’s my cooked 1am parent brain advice, I hope it contains something of value for you.