>The advice to "eat well and exercise" didn't seem particularly insightful
...but it actually makes a world of a difference. I think this is the most important advice and people tend to discard it as generic and useless - the truth is that it's very hard. Being active isn't a big deal, but for a week? For a full month? Full year? Full decade? Being consistent in eating well and exercising is challenging.
The doctor won't set goals for yourself, but if need a number, give yourself one and try improving on it constantly. There are tons of tools, apps, websites to help you. I've always been very active since I was a kid and still am now (~500 minutes of sports/week) and I can already see a big difference with my friends who aren't. And I'm not old at all.
If you decide to start exercising cause you have symptoms, it's probably too late.