Earlier quoted context omitted.
Its not cardiovasuclar, but the top 2 causes of death in the US are tied to obesity, which takes zero time to reduce. You just have to not eat, which is actually time positive. Most humans are just incredibly bad at impulse control.
It can take months to go from obese to not obese through calorie restriction
That said, people can make pretty rapid weight loss without eating. skip eating 1 day a week and that is 30 lbs a year for an average obese man. skip 2 days/week and that is 60 lbs/year.