Akademik

Аппетит приходит во время еды
The more you are interested in doing or having something, the greater your desire for it is. See Чем больше ешь, тем больше хочется (4)
Cf: The appetite comes while (with) eating (Am., Br.). Eating and scratching, it's all in the beginning (Am.). Eating and scratching wants but a beginning (Br.). The more you eat (get), the more you want (Am.). The more you have, the more you want (Am., Br.)

Русско-английский словарь пословиц и поговорок. . 2013.