The Study
The Effects of Different Degrees of Carbohydrate Restriction and Carbohydrate Replacement on Cardiometabolic Risk Markers in Humans—A Systematic Review and Meta-Analysis
This study is like a super-summary of many science experiments where people were randomly put on different low-carb diets. It helps us see patterns, like whether eating fewer carbs leads to weight loss or changes in cholesterol. But because the diets were different in other ways (like how much fat or protein people ate), we can’t say for sure that the carb amount alone caused the changes.
Analysis score
Maximum 100 for a systematic review with meta-analysis.
Where the score came from
When people eat fewer carbohydrates, they tend to lose a little weight, feel better blood pressure, and have healthier fats in their blood—but only if they replace carbs with good fats. If they eat too few carbs and replace them with bad fats, their 'bad' cholesterol goes up, which can be risky.
Where does this study sit?
Reviews of RCTs (Meta-analyses)
Max 100Randomized Trials
Max 90Reviews of Cohort Studies
Max 85Cohort Studies
Max 72Reviews of Case-Control Studies
Max 63Case-Control Studies
Max 58Cross-Sectional & Case Series
Max 50Expert Opinion
Max 546 / 100
Quality score
The highest quality evidence. Systematic reviews and meta-analyses that pool randomized controlled trials, giving the most reliable summary of experimental evidence.
Key takeaways
Summary
Based on the study abstract and findings.
- 1The weight loss is small but real.
- 2The drop in triacylglycerols is helpful, but the rise in LDL cholesterol could increase heart disease risk over time.
- 3Low-carb diets caused 1.3 kg weight loss on average.
- 4HDL ('good') cholesterol went up by 0.08 mmol/L.
- 5LDL ('bad') cholesterol rose by 0.35 mmol/L on very-low-carb diets.
- 6Triacylglycerols dropped by up to 0.27 mmol/L.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
Nutrients
Year
2020
Authors
E. Fechner, E. Smeets, P. Schrauwen, R. Mensink
Related Content
Claims (6)
Eating fewer carbs might help lower your blood pressure if you have high blood pressure.
Eating fewer carbs—like bread, pasta, and sugar—might help you lose about 3 pounds on average compared to eating a normal amount, especially if you're overweight. It could be a helpful short-term strategy to manage your weight.
Eating very few carbs—like on a strict keto diet—can raise your 'bad' cholesterol, especially if you're replacing those carbs with lots of saturated fats like butter and red meat.
If adults swap carbs for saturated fats—like butter or fatty meats—it changes their cholesterol levels in different ways. The kind of food replacing the carbs matters more than just cutting carbs alone.
Eating fewer carbs—especially very low amounts—seems to lower blood fat levels more than eating a little more carbs, which might be better for heart health.
Eating fewer carbs might raise your 'good' cholesterol a little, especially if you replace them with fats or proteins, but it could also raise your 'bad' cholesterol, so it's not clear if this is truly helpful for your heart.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.