Reviewing the Evidence for Intermittent Fasting
A Cochrane systematic review on the outcomes of intermittent fasting for adults with overweight or obesity was recently published. 22 studies (n=1995) were included. Studies needed to be ≥ 4 weeks with follow-up for ≥ 6 months.
Key Findings for Intermittent Fasting
When compared to regular dietary advice:
- little to no difference in weight loss (low certainty evidence)
- little to no difference in quality of life (low certainty evidence)
- little to no effect for reducing body weight by 5% (very low certainty evidence)
- little to no effect on adverse effects (very low certainty evidence)
Related module: In the Obesity Management in Adults (Nov 2024) module, evidence available at the time of printing suggested that there were potential benefits to intermittent fasting on weight loss and metabolic parameters (info point 21).
Lean Mass Changes with Weight Loss
A systematic review and meta-analysis comparing changes in lean mass between intensive behavioural interventions and incretin-based pharmacotherapy (GLP-1 receptor agonists and dual GLP-1/GIP agonists) was recently published in Diabetes, Obesity and Metabolism. The authors defined lean body mass as total body weight minus fat mass weight.
A total of 20 RCTs (n=15,782) involving adults with overweight or obesity and interventions lasting ≥ 12 weeks were included.
Key Findings
There was no significant difference between standard behavioural interventions and the incretin agonists in terms of lean body mass loss. Lean body mass loss may be a physiological result of weight loss. The addition of resistance training to behavioural interventions produced significantly less lean body mass loss.
| Treatment | Lean Mass % of Total Weight Lost | Certainty of Evidence |
|---|---|---|
| Semaglutide | 35.2 | Moderate |
| Tirzepatide | 25.4 | High |
| Liraglutide | 26.8 | Moderate |
| Behavioural interventions | 26.2 | Moderate |
| Behavioural interventions + resistance training | 17.5 | High |
Clinical Recommendations
To maintain lean mass with weight-loss (whether through behavioural or pharmacologic interventions), recommendations include:
- Progressive resistance training with 2 to 3 sessions/week (strong evidence)
- Adequate protein intake spread among meals (moderate evidence)
- Aim for a weight loss rate of 0.5 to 1 kg each week to reduce loss of muscle (moderate evidence)
- Routine body composition monitoring
The authors also recommend particular attention be given to maintain lean mass in older adults and patients with pre-existing risk factors for sarcopenia.
Related Module: Physical activity guidelines and information on sarcopenia (including resistance exercise) can be found in the Snapshots in Body Weight Management and Nutrition module (Feb 2026).