Quick answer: A cat that always seems hungry is either genuinely underfed, has a metabolic condition like hyperthyroidism or diabetes, or has learned that persistent begging leads to extra food.
Compare current portions against feeding guidelines on the food packaging, adjusted for your cat's ideal weight — not current weight if overweight. Many cats on measured portions are genuinely underfed if the food is low in protein or heavily processed. High-protein wet food is more satiating than dry food.
Hyperthyroidism causes increased appetite alongside weight loss — a cat eating more but losing weight is a clear red flag. Intestinal parasites prevent nutrient absorption and cause constant hunger. Diabetes also increases appetite in some stages. Any of these require vet diagnosis and treatment.
Indoor cats with low stimulation often redirect boredom into food-seeking behavior. If your cat begs constantly but maintains a healthy weight, enrichment toys, puzzle feeders, and interactive play sessions often reduce apparent hunger significantly — because boredom was the real driver.
If your cat is hungry and losing weight, see a vet promptly. If they're hungry and maintaining or gaining weight, address enrichment before increasing food portions.