Most of us are under the impression that we know when we are full.  We can accurately determine based on internal cues that we are satiated and do not need to eat any more.  Most of us, however, are wrong.  In a series of studies, Dr. Barbara J. Rolls from Penn State University, has demonstrated that people’s overall consumption of food and internal feelings of satiety are easily manipulated based on portion sizes.  If my levels of being satisfied were based just on internal feelings, whether my sandwich is 6, 8, 10, or 12 inches shouldn’t influence how much of it I eat.  However, studies show that whether eating subs, potato chips, macaroni and cheese or salads, people tend to eat more and need more food to feel satisfied, when there is more food present.   

In Parshat Behar we read about the mitzvah of Shemittah, where we are informed that every seventh year, the land must rest.  Even though we won’t be able to work the land, the Torah tells us (Vayikra 25:19) that G-d will provide nourishment and that we will eat to the point of satiation (“ve-achaltem lasova”).  However, the pesukim continue with what seems to be a redundancy.  “And should you ask, what are we going to eat if we can’t sow the field and gather our crops?” To this the Torah answers that G-d will bless the produce of the sixth year, so that it will yield enough produce for three more years (Vayikra 25:20-21).  But didn’t it just say in the previous pasuk that we will eat to the point of satiety? Why does it then say that if you are nervous, don’t worry - there will be enough food for three years?

Rabbi Ovadia Sforno explains this perceived repetition is really reflecting two potential blessings offered by G-d. The first, and what seems to be the ideal situation, is that G-d will bless the food’s potential for satiety.  The nutritional value will increase, and a smaller dose of food will keep us satisfied longer.  This is similar to what the Sages tell us about the manna, which despite its size, was able to provide adequate nutritional and satiation value.  This is the ideal blessing – smaller portion sizes; longer lasting satiation.  The Torah then adds a contingency blessing.  If our belief is lacking and we are nervous that we won’t be filled by the smaller portions, then G-d will increase the quantity of the food as well.  Our eyes will perceive the vastness of the food and we will feel more comfortable and more satisfied.  

Sforno is highlighting the subjectivity of satiation.  The first blessing would have been enough.  The only impediment to it taking place would be our own nervousness about how small the portions looked. In order to avoid any anxiety related to keeping Shemittah, G-d is willing to give in to this human frailty and give us bigger portions just so we would feel better. Yet, the ideal would be for us to be satisfied with the smaller portion.  

If we can expand from Shemittah to our normal eating habits, the message is clear.  Our ability to feel satiated isn’t entirely biological.  There are psychological processes as well.  Our portion sizes and the environmental cues as to how big are plates and cups are, affect how much we eat before we feel full.  If we can train ourselves in a healthy way, perhaps with the guidance of a nutritionist or a psychologist, we may be able to eat less while still obtaining important nutrients and feeling just as satisfied.