No time to work out? Katz doesn't buy that excuse. Exercise shouldn't be something that we're "making time" for, he says. It should be a daily given, like sleep or eating. "If you want a lifetime of robust health, you have to be religious about your physical activity," Katz says, which, according to HHS, means getting 2 1⁄2 to five hours of moderate cardio, or 75 minutes to 2 1⁄2 hours of intense cardio, each week, plus weight training twice a week. But that doesn't mean you have to slog it out on a treadmill at the gym. Pick a truly enjoyable activity — and a workout partner if you can find one — that will make you sweat and that you can commit to, says Katz. "Put on music for half an hour every evening," he says, "and dance around your house!"