Everyone’s food requirements vary based on their body size, metabolic rate, and health goals. Most adults will need to eat three meals a day plus two snacks. A dietitian can calculate how much food you should eat to meet your weight loss goals. Everyone’s food requirements vary based on their body size, metabolic rate, and health goals. Most adults will need to eat three meals a day plus two snacks. A dietitian can calculate how much food you should eat to meet your weight loss goals.