In a recent study, participants who did one to three HIIT workouts a week saw reductions in fat mass. In fact, new research reveals that just one workout a week could result in meaningful fat loss over time. Potential fat loss isn’t the only reason to consider incorporating HIIT workouts into your weekly mix. The study’s results show that just one workout a week can promote fat loss. First of all, while fat loss may be desirable for some people, it’s not a good barometer of overall health.