No longer wants to eat

Has anyone else's toddler stopped eating well? He will only eat 'treat' foods like fries, crisps and biscuits. Or fruit and yogurt. I'm getting so fed up of making him meals and food getting wasted every night. He used to love things like pizza, cottage pie, spaghetti bolognese, now he won't eat any of it, it's really stressful! It's even difficult to get him to eat toast or pancakes, he just nibbles at it for 1 minute then throws it away.