Photo Credit: Jewish Press

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 level of satiety were based just on internal feelings, the size of my sandwich wouldn’t influence how much I eat of it. However, studies show that people tend to eat more, and need more food to feel satisfied, when there is more food in front of them.


In Parshat Behar, we read about the mitzvah of Shemittah; we are informed that every seventh year, the land must rest. Since we can’t work the land, the Torah tells us that G-d will provide nourishment and we will eat to the point of satiation – “ve’achaltem lasova” (Vayikra 25:19).

However, the Torah continue with what seems to be a redundancy. It states, “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 sixth year so that it will yield enough produce for three more years (Vayikra 25:20-21). But didn’t the Torah just state that we will eat to the point of satiety? Why does the Torah then say that there is no need to worry because there will be enough food for three years?

Rabbi Ovadia Sforno explains that this repetition actually reflects two potential blessings. The first – what seems to be the ideal situation – affects the food’s satiety potential. Its nutritional value will increase, and a smaller dose of food will keep us satisfied for longer. It will be like the manna, which our Sages tell us was able to provide adequate nutrition and satiation despite its small size.

The Torah then adds a contingency blessing: If our belief is lacking and we are concerned that we won’t be filled by the smaller portions, 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 satisfied.

In his answer, the Sforno is highlighting the subjectivity of satiation. The first blessing is sufficient. The only problem is our own worries about how small the portions look. 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 will feel better. The ideal, though, would be for us to be satisfied with smaller portions.

If we can extrapolate 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. Portion sizes and societal views on the proper sizes of plates and cups 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.