There are no downsides to fasting (when done properly and safely).
You’ll lose bloat and a few pounds (probably more, but not guaranteed. You’ll feel better mentally for sure. Once you get used to feeling a hungry your at peace.
My luck with longer fasts not so rosy, 3 days, no problem, when I tried for a week I felt bad on day 4, and developed a wicked case of acid reflux that finally caused me to break the fast at the end of day 5. Hunger was not my main problem. I still look old and fat…so not sure about the looks. I lost about 2 lbs after refeeding. Mental clarity was fine throughout.