Intermittent Fasting (IF) is gaining ever more interest in the UK and Australia, with various celebrities claimed to be doing it, though it does not appear to have become that trendy yet in the USA. There has for some time been serious medical research into the longevity benefits of severe calorie deprivation. Some research now indicates that even occasional severe calorie deprivation can have these benefits, hence 'intermittent fasting'. There are several versions of this, ranging from no food at all for 3 1/2 days every two months, to reducing calories to one quarter of daily needs for two days per week, preferably not consecutive. The latter is called 5:2 (five days of feeding, two days of semi-fasting on c500cals for women, c600cals for men--some versions allow these to be spread over the day, others suggest having these in just one meal, and nothing for the rest of the day). Books on this concept include The Fast Diet by Dr Michael Mosley and Mimi Spencer, The Alternate-Day Diet by James B Johnson, MD and Donald R Laub, MD, and The 5:2 Diet Book by Kate Harrison. There is also lots of information online which you can find by googling 5:2 or Intermittent Fasting. There are different versions of 5:2 which play around with starting and ending times of the semi-fast; 16:8 restricts eating to an 8-hour window every day. The point of all these is to ensure a long stretch of no food intake at all, or severe calorie restriction.
A milder version by Dr Michelle Harvie and Prof Tony Howell is two consecutive days of protein, veggies and dairy up to 50g carbs, which ensures weight loss but does not promise the other health benefits of the more serious calorie restriction of IF, such as controlling cholesterol, diabetes, blood pressure as well as activating cell renewal.
What is crucial in all these versions is that one must eat normally on the other five days of the week. 'Normal' means eating what is necessary to maintain weight. Maybe a small treat, not a binge.
One additional benefit of IF is getting back in touch with one's body's signals, rediscovering the feeling of true hunger rather than eating because of the clock, or boredom, or emotions.
One criticism of IF is that it can lead to obsessing about food, so people with eating disorders are discouraged from attempting it. I think the focus on calorie counting is a part of this problem. My take on this is that one can plan ahead a balanced meal of c500cals (women) such as protein, veggies plus one carb, either whole grains or fruit. This is to be eaten in the evening. From what I've read, the longer the interval without food, the more effective the health benefits. Also, the later one postpones the start of eating, the more tolerable the hunger is. So, no breakfast, just tea/coffee as usual. For the rest of the day, herbal tea, low-cal drinks and lots of water. If hunger becomes intolerable, eat one of the dinner items ahead of time, but then obviously one can't have it again for dinner. Knowing there is a proper meal waiting at the end of the day makes it more bearable, for me, than teasing myself with minuscule "meals" throughout the day. Also, nibbling throughout the day isn't really fasting. On some days I'm so busy that I just don't have the time or the opportunity to eat during the day, so my only main meal is the evening meal anyhow. For IF I would just need to skip breakfast as well. It also helps if the last meal on the previous day is relatively light, e.g. last night I only had fruit and nuts, or even skipped altogether to extend the fasting time. Another possibility is having protein shakes or bars up to 500cals a day, but personally I prefer real food.
There are so many versions of this IF that it is worth experimenting with the different formats to find the one that is easiest to follow. Also, if there is a plateau it may help to switch to a different version for a while. However, I don't think true fasting (only water, no food at all) should be extended beyond 36 hours without medical supervision, and there may be some medical conditions that contraindicate even that long, e.g. diabetes (?).
There is a Spark Team for IF but it appears to be inactive. I have found several 5:2 and IF communities online which are supportive and informative (and free!).