Extreme diets may mean you lose muscle. This new analysis examines whether structured exercise can help preserve it.
Overview
- What did they test? The current meta-analysis tested whether adding structured exercise to a very low energy diet (VLED, ((≤800 kcal/day)) reduces the loss of fat-free mass compared with the VLED alone in adults with overweight or obesity.
- What did they find? Exercise was associated with significantly greater fat-free mass retention, with an average benefit of 0.83 kg versus diet-only. Subgroup analyses did not identify a clear advantage for aerobic, resistance, or combined training.
- What does it mean for you? In practice, well-designed resistance training paired with adequate or high protein intake is the best way to retain lean mass during rapid weight loss.
What’s the Problem?
VLEDs have been used for decades as a clinical strategy for rapid weight loss. They are typically defined as diets providing ≤800 kcal per day, often delivered through meal replacements, and are usually implemented under medical supervision 1 2. The large caloric deficit drives substantial and rapid reductions in body mass, but adherence can be challenging due to hunger and fatigue.
One of the major drawbacks of rapid weight loss is that reductions in body mass are not limited to fat. A proportion of weight lost during energy restriction can come from fat-free mass (FFM), with estimates suggesting that 20–30% of total weight loss may be attributable to lean tissue, particularly as the severity of the caloric deficit increases 3 4.
Exercise, and resistance training (RT) in particular, is widely viewed as a key countermeasure to lean mass loss during dieting. Indeed, RT helps preserve skeletal muscle during negative energy balance, and meta-analytic evidence consistently shows greater retention of FFM when exercise is combined with dietary weight loss compared with diet alone 5. Physique athletes often maintain most of their lean mass during contest preparation, and in some cases individuals can gain lean mass while losing fat when resistance training is paired with sufficient protein intake 6. Body recomposition has even been documented in trained populations under specific conditions, challenging the notion that muscle gain is impossible during an energy deficit 7. That said, most people just want to keep their muscles when they diet.
Purpose
The objective of this systematic review and meta-analysis was to determine whether the addition of exercise reduces FFM loss during VLED-induced rapid weight loss in people with overweight or obesity.
Hypothesis
The authors did not state a specific hypothesis.
