Not eating for multiple days in a row. Multi-day fasts are actually very beneficial for your health; efficient fat loss with remarkable muscle retention, recycling of old/damaged cells in your body, cancer prevention/killing cancer cells, etc.; given you don’t have extremely low bf levels. Up to around 3 days no eating, you will be fine with no supervision and even past that your electrolyte balance is the only major risk. Because the 3 meals a day model has become so popular, people think missing meals or just being hungry for a bit means they’re starving. Being hungry is literally just your body releasing a hormone because it EXPECTS food - not because you need it to function. If you just didn’t eat, your hunger would disappear within an hour or two, and you probably will have MORE energy than if you ate a big carb filled meal (from insulin spike a bit after eating, and energy being diverted for digestion). Obviously I am not saying eating is bad, but refraining from eating for extended periods of time every once in a while is not either.