Actually I’d advice them to stop being sedentary first. Lots of benefits to that. Lower your heart rate, increase your calorie burn, keep your strength up so you don’t wind up helpless when you get older (a frightening percentage of people over 60 can’t pour a glass of milk from a gallon jug, not enough arm strength). On the diet side just reduce EVERYTHING. Really, Americans eat too much. 2/3 reduction across the board would do most people a world of good. then you don’t have to be all weird avoiding yummy food all the time. Just eat less.
You can’t outrun a bad diet.
Especially the processed junk.
One of the benefits of Keto is that if done right, pretty much eliminates processed food, yes I know technically you can eat Pork Rinds, and that garbage, but clean Keto is basically grass-finished beef, fish, green leafy vegetables, avocados, nuts, and eggs.
And I “cheat” by making chocolate treats with 100% Cacao powder and Swerve sweetener.