What is already known?

Very low-energy diets (VLEDs) have been implemented successfully primarily as a means of improving body composition, but also to improve metabolic parameters.

However, as a consequence of profound energy restriction, VLEDs are associated with reductions in lean body mass (LBM).

Theoretically, additional protein in LEDs will result in enhanced retention of LBM.

Based on distinct physiological adaptation, differing forms of exercise will likely exert different effects on lean body mass retention during LEDs.

What are the new findings?

Resistance exercise training (RET) may significantly improve LBM retention during LEDs, although the precise effect and magnitude are unclear.

The reported effects of aerobic exercise training (AET) on LBM preservation during LEDs are conflicting.

Currently, there are insufficient data to report the effect of high-intensity interval training (HIIT) on LBM retention during LEDs.

There are also inadequate data to discern the effect of additional dietary protein during LEDs with exercise.