Why it works: The RDL, as it's known, is primarily a hamstrings move, but it’s also effective in building strength in your glutes, lower back, and upper back. Be sure to feel the "squeeze" in your hamstrings and glutes as you raise and lower the bar. For an even tougher variation that'll also increase your grip strength, try doing tempo RDLs—count a few seconds on your way up, and on your way down.
But muscle can’t turn into fat, just like mud can’t turn into gold. If you quit lifting, your muscles mass will decrease over time because there’s no training to stimulate your body to keep it. And your body-fat level will increase if you don’t start eating less (since you burn less). The obvious solution when you stop lifting is to also stop eating so much.
Note that this recommendation is for total weekly volume, which means it would need to be divided up based on how many times you’re training each muscle group per week. So, for example, someone training everything twice per week would do 30-70 reps for each bigger muscle group in each of those workouts, and 15-35 reps for each smaller muscle group in each of those workouts.