Well, it's probably not one of the healthier ways to diet for weight loss; it can relate to disordered eating. But the ignorance is a cultural issue.
You want to know what fasting does? Ask the people who do it routinely. Muslims and Baha'is both have a fasting month when they don't eat between dawn and dusk. Buddhism includes various sorts of fasting, especially for monks and nuns. Hinduism also has a variety of fasting customs. Some other cultures use it too. Look at their records. Talk to their practitioners, especially holy people who are more likely to fast than lay practitioners; and talk to doctors who serve them. Examine their records. I would bet they've done studies on this, although you might need someone who reads Arabic or Hindi to translate them, to say nothing of studies done in smaller languages. Some cultures have been at this for thousands of years and have a large archive of spiritual materials, including those about fasting. Notice how much overlap there is in customs, especially exemptions and prohibitions on who must or may fast. If you are determined to fast, you are less likely to get into trouble with it by following a custom that's been around for thousands of years than by following this week's fad, although the exact safety depends on the individual custom and your particular body.
"We don't know anything about this" is probably a different way of saying "I don't know any brown people" or "I'm not asking those people, they don't know anything." Yeah, right, the Muslim nurse who scrapes up the overzealous fasters every Ramadan knows nothing about the effects of fasting. :/
Meanwhile over in Terramagne, the imams in the Maldives noticed immediately when the influx of immigrants -- especially soups -- spiked the number of people faceplanting during Ramadan. They got together and acknowledged that superpowers run up the calorie demand for most soups. The typical range for calorie-powered abilities is around 2-4 times the average rate, but high-burn powers can cost more and even people whose abilities don't run mainly on calories may need half again the usual. So what the imams did was calculate the time of fasting based on an average calorie requirement, which allowed them to project the comparable time of fasting for other calorie requirements. If you need twice the calories, you fast for half the time, and so on. The high-burn soups, especially speedsters, really shouldn't fast. But that's okay! Islam provides an alternative: feeding one poor person for each day of a required fast, which is called fidiya, and may be calculated as in zakat al fitr. The Maldivian interpretation includes food, money to buy food, or labor providing food such as cooking; so everyone has some way to do this.