Its a Russian proverb which tells the importance of having breakfast . one should not skip breakfast for any reason , you can skip even lunch and dinner but not morning breakfast , its the first food which going to give you enough fuel of energy to run that day .. . .
You should eat well in the breakfast since it's the beginning of the day, lunch little less than that but you must eat very little in the evening as it's healthy not to eat too much in the evenings. Logically, if you eat alone, that means you eat more because you don't have to share, if you eat with a friend, that means you'll share with him or her so you'll eat less in the lunch. And for the dinner, you'll give your meal to your enemy meaning you should eat very little.