Researchers compared six popular diets to see which one helps people with metabolic syndrome the most. Metabolic syndrome is a group of health problems that includes extra belly fat, high blood pressure, and unhealthy cholesterol levels. Scientists looked at 26 studies involving 2,255 people and found that three diets stood out: the vegan diet was best for reducing belly fat, the ketogenic diet worked best for lowering blood pressure, and the Mediterranean diet was best for controlling blood sugar. The good news is that multiple diets can help, so people can choose one that fits their lifestyle.

The Quick Take

  • What they studied: Which diet plan works best for helping people with metabolic syndrome (a combination of health problems including belly fat, high blood pressure, and bad cholesterol)?
  • Who participated: 2,255 people across 26 different research studies who had metabolic syndrome. The studies tested six different diet types: vegan, ketogenic, DASH, Mediterranean, low-fat, and low-carb diets.
  • Key finding: Three diets showed the strongest benefits: vegan diets reduced belly fat the most, ketogenic diets lowered blood pressure the most, and Mediterranean diets controlled blood sugar the best.
  • What it means for you: If you have metabolic syndrome, you have options. Different diets work better for different health problems, so you can pick one that matches your biggest health concern and your food preferences. However, talk to your doctor before making major diet changes.

The Research Details

Researchers conducted a network meta-analysis, which is a special type of study that combines results from many different research projects to compare treatments. They searched eight major medical databases for studies published up until April 2025 that tested different diets on people with metabolic syndrome. They only included high-quality studies where people were randomly assigned to follow different diets (called randomized controlled trials). This approach is stronger than looking at single studies because it combines evidence from thousands of people across many different research teams.

The researchers used special computer software to analyze all the data together and compare how well each diet worked compared to regular eating habits. They looked at specific health measurements like waist size, blood pressure, cholesterol levels, and blood sugar control. By combining all these studies, they could see patterns that might not show up in any single study.

This research approach matters because it’s hard to know which diet is truly best when different studies test different diets. By combining all the evidence together, researchers can make stronger conclusions about which diets actually work. This helps doctors and patients make better decisions instead of relying on just one study or personal opinions.

This study is fairly strong because it included 26 randomized controlled trials, which are considered the gold standard in medical research. The large number of participants (2,255 people) makes the results more reliable. However, the study only looked at published research, so some unpublished studies weren’t included. The studies came from different countries and used slightly different methods, which could affect how comparable they are. The researchers were transparent about their methods and registered their study plan in advance, which is a good sign of quality.

What the Results Show

The vegan diet was the clear winner for reducing belly fat, shrinking waist circumference by about 12 centimeters more than regular eating. The DASH diet (Dietary Approaches to Stop Hypertension) also worked well for belly fat, reducing it by about 5.7 centimeters more than normal eating.

For blood pressure, the ketogenic diet was the strongest, lowering the top number (systolic pressure) by about 11 points more than regular eating. The DASH diet also helped, lowering systolic pressure by about 6 points. When looking at the bottom number (diastolic pressure), the ketogenic diet was the only one that showed significant improvement, lowering it by about 9.4 points.

For cholesterol and blood sugar, the vegan diet helped raise good cholesterol (HDL), the ketogenic diet was best at lowering triglycerides (a type of fat in blood), and the Mediterranean diet was best at controlling fasting blood sugar levels. These findings suggest that different diets excel at different health improvements.

The low-fat diet and low-carbohydrate diet showed some benefits but weren’t as effective as the top three diets. The Mediterranean diet, while excellent for blood sugar control, didn’t rank as high for belly fat reduction or blood pressure lowering. This suggests that no single diet is perfect for all aspects of metabolic syndrome, and the best choice depends on which health problem is most important to address.

Previous smaller studies had suggested that all six diets could help with metabolic syndrome, but this is the first large comparison showing which ones work best for specific problems. This research confirms what earlier studies suggested but provides clearer rankings. It also shows that people don’t need to choose between these diets based on general claims—they can choose based on their specific health needs.

The studies included came from different countries and used different methods, which could affect how well the results apply to everyone. Some studies were longer than others, and people in different studies may have followed the diets differently. The research only looked at published studies, so studies with negative results that weren’t published might be missing. Most studies were relatively short-term, so we don’t know if these benefits last for years. The study couldn’t prove that diet caused the improvements—only that they were associated with them.

The Bottom Line

If you have metabolic syndrome and want to reduce belly fat, try a vegan or DASH diet (moderate to strong evidence). If high blood pressure is your main concern, the ketogenic or DASH diet may help most (moderate to strong evidence). If controlling blood sugar is most important, the Mediterranean diet shows the strongest benefits (moderate evidence). Talk to your doctor or a registered dietitian before starting any new diet, especially if you take medications.

This research is most relevant for adults with metabolic syndrome who want to improve their health through diet. It’s also useful for doctors and nutritionists helping patients choose a diet plan. People with specific health conditions (like kidney disease or diabetes) should consult their doctor before trying these diets. If you’re pregnant, nursing, or have other health concerns, talk to your healthcare provider first.

Most studies showed improvements within 8-12 weeks, but benefits often continue to build over several months. Don’t expect overnight changes—give yourself at least 4-6 weeks to see noticeable improvements in measurements like waist size or blood pressure. The longer you stick with the diet, the better the results tend to be.

Want to Apply This Research?

  • Track weekly waist circumference measurements and blood pressure readings (if you have a home monitor). Record which diet you’re following and note any changes in energy levels, hunger, or how your clothes fit. This creates a personal record of what works for your body.
  • Choose one specific diet to try for at least 6 weeks based on your main health goal. Use the app to log meals according to that diet’s guidelines, set reminders for meal prep, and track your chosen health metric weekly. Share your progress with your healthcare provider.
  • Set up weekly check-ins to record your waist measurement and blood pressure. Create a monthly summary view showing trends over time. If you’re not seeing improvements after 6 weeks, discuss with your doctor whether to continue, adjust, or try a different diet approach.

This research summary is for educational purposes only and should not replace professional medical advice. Metabolic syndrome is a serious health condition that requires personalized treatment. Before starting any new diet, especially the ketogenic or vegan diets, consult with your doctor or registered dietitian, particularly if you take medications, have diabetes, kidney disease, or other health conditions. Individual results vary, and what works for one person may not work for another. This study shows associations between diets and health improvements but doesn’t prove that diet alone caused the changes. Always work with your healthcare team to develop a treatment plan tailored to your specific needs.