High-intensity interval training (HIIT), often called interval training, is frequently promoted as a time-efficient and effective method for fat loss, standing in contrast to the more traditional moderate-intensity steady state training. But how well does interval training really work for fat loss, and is it better than continuous training?
Interval training involves short bursts of intense effort, usually at or above 80% of peak heart rate, interspersed with recovery periods. These sessions are highly adaptable, ranging from all-out sprints to cycling intervals. Continuous training, on the other hand, consists of sustained, moderate-intensity activity (e.g., jogging or cycling) performed at 50–70% of max heart rate for extended durations.
The distinction lies in intensity, duration, and structure. Interval training prioritizes maximizing effort in minimal time, while continuous training takes a steadier, more prolonged approach. Both methods improve health markers, but their comparative effects on fat loss have generated some debate.
What does the evidence say?
A systematic review and meta-analysis comparing the effects of interval and continuous training on fat mass found no meaningful differences between the two approaches. Both interval and continuous training led to small reductions in fat mass, with interval training showing slightly greater, but not significant, results. For example, fat loss associated with interval training ranged from 0.2–0.4 kilograms, compared to 0.1–0.3 kilograms for continuous training. These findings suggest that neither method holds a decisive advantage when total calorie expenditure is matched.
Interestingly, interval training might offer specific benefits for reducing abdominal fat. This effect, though not universally observed, could result from the higher intensity stimulating greater hormonal responses linked to fat mobilization. However, more research is needed to confirm these claims and understand the mechanisms involved.
Practical considerations
Interval training is often marketed as a time-efficient option. A typical session lasts 15–30 minutes, including recovery periods, making it appealing for those with busy schedules. In contrast, continuous training sessions often range from 30–60 minutes to achieve similar energy expenditure.
While interval training offers brevity, its intensity may deter some individuals. Adherence may end up being lower in programs requiring maximal effort, particularly among untrained individuals or those with lower exercise tolerance. Additionally, high-intensity training may impose an added recovery burden, potentially making it harder to recover from lifting, especially for those already facing recovery challenges such as being in a calorie deficit. Continuous training, with its steadier pace, may be a more sustainable option for certain populations.
For sedentary individuals or those new to exercise, continuous training provides a safer and less intimidating starting point. Experienced exercisers, on the other hand, may benefit more from the metabolic and cardiovascular challenges of interval training.
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Have a great rest of your week.
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The SBS Team
Greg, Pak, Milo, and Lyndsey
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