Foremost among the macrobiotic beliefs is that the Western diet is unbalanced in the aspect of yin/yang foods that are eaten.  No food is forbidden in the macrobiotic diet, but many are not recommended for frequent consumption.  Yin foods are stimulating foods such as sugar, alcohol, honey, coffee, chocolate, hot spices, preservatives, and dairy products.  Yang foods are strengthening but sedating in overconsumption and include things such as poultry, meat, eggs and refined salt.

Another key belief is that locally grown food products should be consumed whenever possible.  This is due to the belief that the human body has adapted specifically for the climate that it lives in.  Therefore, eating oranges grown in Florida when you live in Alaska forces your body to adapt to food from a climate that it is not familiar with, creating additional strain on the body.  This is most key in foods that are strong in yang energy, as these tend to be foods that are preserved more easily (grains, salt, meats) rather than foods strong in yin (fruits and vegetables).

The belief that diet should change with the seasons is also key to the macrobiotic diet.  For instance, in the spring and summer most of our fire energy is contributed directly from the sun so the diet should consist of foods that require less heat to prepare.  Conversely in the autumn and winter, less fire energy is gained from the sun so more is required from the preparation of our foods, resulting in warmer, heartier meals.  However, preparation is not the only dietary aspect that should change with season.  Foods can be eaten in plenty when they are plentiful, but should be consumed in lesser amounts when they are out of season.  For example, when fruits and vegetables are plentiful in the spring and summer they can be eaten as desired but should be more strictly regimented in the autumn and winter.

It should also be mentioned that one food group that is strictly discouraged by the macrobiotic diet is the nightshade vegetable group.  This includes tomatoes, peppers, potatoes, eggplant, spinach, beets and avocados.  These vegetables are thought to be extremely yin and should be avoided altogether or at best used sparingly.

There are a total of 10 diets set down by George Ohsawa which vary in composition from 100% grains to 10% grains.