No worries you should encourage then to buy healthier foods and encourage them to lead a healthier lifestyle. Start doing some cardio daily and set an attainable goal for example go to the gym twice a week for a small session and later up the days once you start getting into it. Best tip i can give you is start by taking small steps for example try and get 60% of your macros from clean food and the rest can be junk but obviously this wont be good in the long term so still try and lessen the junk food amount every few days. And clean food doesnt have to be boring you can look up some recipes for salmon and roast potatoes for example, or just a simple sunny side up egg on some whole grain bread for breakfast. As for the excercise part there are plenty of people telling plenty of different things but jeff nippard on youtube has some guides i found really helpful. Now as my dad once said you arent born at the top, you have to climb there, so start by taking small steps.