Eat, Fast, and Live Longer looks at a variety of medically supervised diets. The goal is to decrease risk for various things. In the past I've used the alternate day fasting successfully, though over time the weight I lost came back - but the bum knee was fixed right at the beginning of COVID so my mobility is restored, which is a huge help). I was doing it primarily to reduce cholesterol with the side benefit of losing a few pounds. Probably a "stone" for the UK crowd.

Successful alternate-day fasting tends to be seasonal - I wouldn't do it year round. Fasting in cold weather is difficult when your body naturally is trying to hold onto calories to keep you warm. A veterinarian friend made that observation that seems to be true, though wasn't discussed in the hour-long documentary. Lose weight in warmer weather and just try to maintain the level during cold weather.