It's 16 h:
> restricting daily food intake to an 8-hour timeframe […] As long as 16 hours of fasting were maintained
Eating was restricted to an 8h window. Fitting 3 meals into an 8h window would be … tricky. I feel like most people's schedule is "[breakfast], [work], [dinner]" (with lunch in the middle of work), and assuming you work 8h, then you're already outside the study's fasting window. Throw two commutes in there …
That's the main secret to time restricted eating, in my opinion: You don't have enough time to eat as much as you normally do so overall calorie intake tends to decrease. I think the other reason it's helpful for some people is that eating nothing for one meal takes less self control than restricting yourself to a small portion, leading to better adherence than normal calorie counting.
There’s a big difference between “I’m malnourished”, “My body feels hungry” and “I want to eat for reasons other than feeling hungry”. Intermittent fasting will definitely teach you what “My body feels hungry” feels like, and shows you how to suppress it for hours.
I think the positive reinforcement of eating during the time window also helps in this learning process.
What I find fascinating about hunger is how it interacts with your subconscious. You start daydreaming about food. If you're not paying attention you'll find yourself standing in front of the pantry.
When I'm hungry I feel like my conscious mind is wrestling with my subconscious.
I find being slightly hungry makes me mentally sharper. It’s a fine line though, as symptoms such as irritability, daydreaming, loss of focus, poor memory recall, and reduced critical thinking skills will accumulate over time.
Edit: As a sibling comment says quite rightly, you do feel hungry in the late morning, but reacting to that feeling is optional
But it's also very contexy sensitive: currently working from a place where I usually go for high calorie throughput sports (think Tour de France climbs, but higher and a heavier rider, obviously a lot slower but the energy demand is mostly mass x elevation, almost unpacked to speed) and my body is in "eat! you will need it!" mode every day. Crazy weight gain on the working days.
You would probably fit a snack and meal into that period. It could be a really big meal, and it would still probably be significantly less calories than breakfast, lunch, and dinner.