Both of those statements are wrong. First of all, in studies of people who have fasted for a day or have skipped a meal, reported eating only slightly more than they would ordinarily eat, when they finally had a meal after fasting or after skipping the previous meal. Also, research has shown that even extreme fasting for three days in the row, will not slow down the metabolic rate. J. Webber and I. A. Macdonald, “The cardiovascular, metabolic and hormonal changes accompanying acute starvation in men and women,” British Journal of Nutrition, 71, no. 3 (March 1994)
Many people also find letting their body go hungry very uncomfortable. That is true, but the discomfort is temporary, the benefits are permanent. Think of it as a withdrawal. If you are a coffee drinker, you know what happens if you don't drink your coffee. You get a headache because your body goes through a caffeine withdrawal. This is temporary and manageable. You see, most people have never felt true hunger because they eat all the time, so when they take a break from eating they go through some discomfort similar to a withdrawal. The good news is once your body adjusts, you will not believe how good you will feel and how much more energy you will have. I know, because I have been through it myself. It definitely worth the minor discomfort you may go through.