How much fat do you lose in 7-days on 850 kcal/day? 📉

Comparison of two aggressive fat loss diets.

Tom Coughlin

Oct 10, 2025

Study Details

This new study recruited 46 healthy men and women who were assigned to 7-day diets of either…

1️⃣ Low-protein / high-fat (LP: 850 kcal, 10% protein, 45% fat)

2️⃣ High-protein / low-fat (HP: 850 kcal, 30% protein, 25% fat)

3️⃣ Control (isoenergetic diet)

DEXA scans for body composition, markers of cardiovascular health and autophagy were analysed pre- and post-diets 🔍

Here is what they found ⬇️

Key Findings

Compared to control, both low-calorie diets significantly reduced…

⚖️ Body weight (LP: -2.44 vs HP: -2.73 kg)

🩻 Fat mass (LP: -0.68 vs HP: -0.98 kg)

🩸 Fasting blood glucose (~10%)

🧬 IGF-1 (~35%)

…and lean mass (both ~1.76 kg loss)🚨

But only the HP diet reduced visceral fat mass (-0.15 kg) 🩻

Plus only the HP diet led to significant improvements in…

🫀 HRV

🦠 Gut microbiome diversity

🩸 Circulating triglycerides

🧈 Saturated fatty acids

Serum hydroxybutyrate was higher in the LP vs HP 📈

Both low calorie diets induced autophagy at the molecular level ☠️

Conclusion

A short term very low calorie (850 kcal) high protein (30% of energy) diet can optimise body fat losses over 7-days (~1kg loss) ✅

Plus leads to improved cardiovascular markers compared to a higher fat diet🩸

Although this level of protein was not enough to maintain lean mass during weight loss‼️

Reference

https://pubmed.ncbi.nlm.nih.gov/40816210/

Performance Nutrition Digest is powered by Healthspan Elite ⚡️

Healthspan Elite is a science-led sports nutrition range developed in collaboration with leading experts to support athletic performance, recovery, and health.

Use code: TCDIGEST25 for 25% off at https://www.healthspanelite.co.uk/ 💪