It is our purpose in life to come close to God through studying Torah and by keeping the commandments. In this way the soul is elevated and merits eternal goodness in the World to Come. However, in order for the soul to exist in the material world, it must be clothed in a body through which the soul may achieve its purpose. For this reason we must supply the body with its essential needs like food, water, sleep, and exercise, without which the body could not exist and the soul could not fulfill its potential.
This is the meaning of the Torah commandment "Be very careful to guard your soul" (Deuteronomy 4:15). In fact, our Sages considered this mitzvah so important that they equated it with the commandment to remember the giving of the Torah: On the verse "Guard yourself and greatly guard your soul lest you forget…the day that you stood before Hashem your God at [Sinai]" (Deuteronomy 4:9-10), the rabbis explained "guard yourself" means preserving one’s health.
Maimonides (Rambam), the great Torah scholar and physician of the 12th century, wrote: "maintaining a healthy body is among the ways of serving God, since it is impossible for one who is not healthy to understand or know anything of the Creator. Therefore one must distance oneself from things which harm the body, and accustom oneself to the things which strengthen and make one healthy."
On exercise the Rambam says, "As long as a person exercises and exerts himself…sickness does not befall him and his strength increases…. But one who is idle and does not exercise…even if he eats healthy foods and maintains healthy habits, all his days will be of ailment and his strength will diminish." If this is so regarding the era of the Rambam when even daily life was physically demanding, all the more so in our times when technological progress "spares" us much exertion.
Regarding what type and how much exercise one needs, the Torah approach is to rely on the advice of the experts. The Rambam defined exercise as "vigorous or gentle movement, or a combination of the two, which increases one’s breathing rate." Interestingly, this is exactly the type of cardiovascular exercise advised by modern medicine like walking, jogging, dancing, biking, or swimming for 30 minutes at least three times a week.
While exercise is vital, the Torah teaches an even more important way to preserve our health: "If you listen to the word of Hashem your God and do what is just in His eyes, give ear to His commandments and observe all His decrees, then the diseases that I placed upon Egypt, I will not bring upon you, for I am God your healer" (Exodus 15:26). The Zohar teaches that the 248 positive Torah commandments correspond to the 248 "limbs" of the human body while the 365 Torah prohibitions correspond to the 365 "sinews". Keeping the mitzvot brings the body in healthy balance with the spiritual energy of the Torah. In fact, serving God actually brings blessing into our daily food, which also protects our health: "You shall worship Hashem your God and He shall bless your bread and your water, and remove illness from your midst" (Exodus 23:25).
