Forced labor camps.
I would ban guns, because obviously guns cause obesity, heart disease, cancer, STD's, and all the other malady's in the US which MUST kill many times more people each year than school shootings because gun control seems to be all anyone talks about these days.
I'd promote exercise, getting kids off their duffs and running around outside. PE programs in schools have been cut back, and I don't know whether they are still doing the President's Physical Fitness Tests in schools, but they should be. Physical activity is of huge importance, and any programs that get kids away from computer and gadget screens and push movement would be my priority.
I wouldn't take any, there is not much you can do to stop it. It's people's own personal choice
Stop the "Body Positivity" movement
I would make sure that M.D. understand all the diseases that cause weight gain.Also all of the weight gaining medications.
Don't put people who are overweight on meds that make them gain more weight.
I would also put out several meal plans at different calorie and carb counts so people understand what they should eat.
First I'd bring home economics back to the schools and gym. These kids would be taught how to read the nutritional labels and actually taught how to cook healthy meals. For those who aren't in school who haven't learned, they would be required to learn in a kitchen at a community college especially if they receive assistance and shown how to stretch those dollars. They would be required to receive counseling and a nutritionist and would get a discount on a gym membership plus a fitness instructor for a year. Oh and they'd receive a large crockpot and given several recipes of their choosing amongst a good selection provided.