Rigorous Honesty, in the search of recovery from gross obesity. Mainly opinion, not advice. Some speculation, some errors, some fiction.
Sugar, grain and processed products are not food. Omega 6 oil and dairy should be mainly avoided.
To make intermittent fasting work, one would need willpower to overcome nature, hunger, and absence of cravings. Hunger, for the first two days may be a problem, especially where food is available and offered. Also, without support, it becomes a singular event, making it even more difficult. With "religious" fasting, is a social event, and that may make it easier.