That is mostly different but the nomenclature is confusing. The orthodox christian tradition of fasting is rarely ever strictly fasting in the medical sense. What they mean is voluntary abstinence from certain kinds of food on certain days, with the specifics varying by tradition & individual particulars.

Most lay orthodox christians only "truly" fast before taking communion and around a few particularly important holidays. So when they talk about fasting they are not normally talking about something that resembles intermittent fasting in practice.