“It’s Not Just What You Don’t Eat … It’s What You Do Eat”
A June 18, 2025 systematic review in The BMJ—covering 99 randomized trials and over 6,500 adults—found that intermittent fasting (IF) and continuous energy restriction (CER) led to only small average weight losses compared to eating freely. Alternate‑day fasting showed slightly greater weight reduction (~1.3 kg more than CER), but did not reach the clinical threshold of a 2 kg difference for people with obesity. In both short‑term (under 24 weeks) and longer‑term studies (24+ weeks), IF wasn’t notably superior to traditional calorie‑cutting approaches.
Key Takeaways:
Tiny gains: On average, only 0.5 – 2 kg difference sustained over a year between fasting, calorie restriction, or even Mediterranean‑style eating.
High dropout rates: Most studies report declining adherence, particularly in longer studies.
It's not about the method: Weight loss appears driven by overall calorie reduction, rather than whether you skip meals or restrict timing.
Why Diet Alone Isn’t Enough
Given modest results even among those who stick it out, we must ask: What else matters?
Food quality and processing: Ultra‑processed foods may blunt satiety and disrupt gut health.
Access & affordability: Not everyone has equal access to high‑quality, minimally processed foods.
Preparation methods: Cooking techniques matter—steaming, fermenting, home‑cooked meals support better metabolism and microbiome health.
Microbiome resilience: Focusing on what to include—fiber, polyphenols, fermented foods—can support gut integrity and reduce cravings.
The idea of “crowding out” ultra‑processed foods by emphasizing real, nourishing foods is powerful. It shifts from a mindset of restriction to one of abundance, and that likely boosts both health and sustainability.
A Balanced and Practical Approach
12‑hour overnight fast: Allowing the digestive system to rest is supported by circadian rhythm research and may enhance metabolic regulation.
Flexible eating models: If fasting feels good (e.g., fewer gut symptoms), great—but there’s no magic bullet for weight loss.
Prioritize quality over calorie counting: Emphasize whole grains, legumes, vegetables, healthy fats, fermented foods.
Leverage structure—not rigidity: Crowding out processed fare with real food is simpler and more sustainable than complex rules.
Context matters: Your social environment, food access, cooking routines, and food system infrastructure all shape outcomes.
So where can we go from here?
Experiment with sensible approaches: Try a 12-hour fast or simplified eating window—but focus on adding quality foods.
Build habits around inclusion, not deprivation.
Explore your food environment: Is your pantry and fridge full of ultra‑processed products?
Advocate system-level change: Support policies that improve access to real food, cooking education, and healthy defaults.
Final Word
Intermittent fasting is not a superior weight‑loss tool—according to the latest BMJ evidence, it’s just one of several methods that reduce calories modestly and real transformation happens when we shift from restriction to nourishment, and when our food systems enable healthy choices in everyday life.
Reference
Semnani‑Azad Z, et al. Intermittent fasting strategies on body weight and other cardiometabolic risk factors: systematic review and network meta-analysis of randomised clinical trials. BMJ 2025;389:e082007. DOI:10.1136/bmj-2024-082007