Energy balance is the primary determinant of changes in body weight. To lose weight, an energy deficit must be established. From a dietary standpoint, this is generally best accomplished by reducing energy intake from fat and/or carbohydrate while maintaining a relatively high protein intake to help preserve lean mass.
Cardio is commonly recommended as an adjunct to dietary restriction to enhance fat loss. However, there has been considerable debate as to whether moderate-intensity continuous training or high-intensity interval training is superior in this regard. Our group conducted a systematic review and meta-analysis to help answer this question (https://t.co/u6gyEOI1mY).
Pooled results from 54 studies indicated that both interval training and MICT reduced body fat, with little evidence that either approach was meaningfully superior for improving overall body composition. HIIT showed a small advantage for reducing absolute fat mass in some analyses, but the magnitude of the difference was modest and of questionable practical significance. Neither HIIT nor MICT produced meaningful changes in fat-free mass.
It is important to note that the individual studies showed considerable heterogeneity, with substantial variation in interval protocols, exercise modalities, intervention durations, participant characteristics, and dietary control. These factors should be considered when interpreting the pooled findings and temper the strength of confidence in conclusions.
Take-home: Current evidence provides no compelling support for a single “best” form of cardio for fat loss. Both interval and continuous training can produce modest improvements in body composition, so the choice can largely be based on individual preference, tolerance, and time availability. The primary advantage of interval training appears to be its time efficiency rather than an appreciably greater effect on fat loss.
Perhaps most importantly, the relatively small absolute amount of fat loss typically achieved through cardio alone reinforces the importance of nutritional control when fat loss is the primary goal. In practical terms, creating a meaningful energy deficit is generally much easier through reducing energy intake than through attempting to expend an equivalent number of calories via exercise.