Now they call it EpiGenetics
You actually are what you think… with a catch…
Conscious thought is only about 5% of the total of what your mind is doing constantly. Your dominant thoughts are not what you consciously think they are. In fact, there is a whole hard-drive of programming that runs your life, and sends signals to your cells, that you are not aware of consciously. Some of that is the programming for your heart-beat and your breathing and digestion but there is also a lot of stuff that was put there between 0 and 7 years, and even some during gestation, that formulate default processes and responses to your environment.
They are editable but what is required, and what I find Bruce Lipton does not have a good practical handle on, is a dashboard interface to communicate directly to that subconscious.