Researchers analyzed 174 studies involving over 11,000 people to see how low-carbohydrate diets affect heart health and body weight. They found that eating fewer carbs significantly lowered triglycerides (a type of fat in blood), blood pressure, and inflammation markers while increasing good HDL cholesterol. People also lost weight and body fat. However, LDL cholesterol (the “bad” kind) increased slightly. The benefits were strongest for women and people with extra weight, especially when diets combined both fat and protein as carb replacements. The findings suggest low-carb diets can improve health, but people should monitor their cholesterol levels with a doctor.

The Quick Take

  • What they studied: How eating fewer carbohydrates affects heart health markers (like cholesterol and blood pressure) and body weight compared to eating more carbohydrates
  • Who participated: Over 11,000 adults from 27 countries across 174 different research studies. The studies included people of different weights, ages, and health conditions, including some with diabetes
  • Key finding: Low-carb diets reduced triglycerides by about 15 mg/dL, lowered blood pressure, increased good cholesterol, and helped people lose weight. However, bad LDL cholesterol increased slightly by about 5 mg/dL
  • What it means for you: If you’re considering a low-carb diet for weight loss or heart health, it may help—especially if you’re a woman or overweight. However, you should get your cholesterol checked regularly with your doctor, as LDL cholesterol may rise. The benefits seem strongest when you replace carbs with both healthy fats and protein

The Research Details

This is a meta-analysis, which means researchers looked at 174 different studies that had already been completed and combined all their results together. Each of these studies compared people eating low-carb diets (getting 45% or less of their calories from carbs) to people eating higher-carb diets. The researchers followed strict guidelines to make sure they only included high-quality studies. They looked at how different types of low-carb diets worked (very strict ketogenic diets versus moderately low-carb diets) and whether results changed based on who was doing the diet (men versus women, people with diabetes versus without, etc.). They also checked whether the length of the diet affected the results.

By combining results from many studies instead of looking at just one, researchers can see the bigger picture and be more confident about what works. This approach helps identify which types of low-carb diets work best for different people and what side effects to watch for. It’s like asking 174 different doctors what they found instead of just one

This study is very thorough—it included over 11,000 people across many countries, which makes the findings more reliable. The researchers followed strict scientific guidelines (PRISMA standards) for how to conduct the analysis. However, the individual studies included varied in quality and length, which means some results are more certain than others. The fact that they registered their analysis plan beforehand (on PROSPERO) is a good sign of scientific integrity

What the Results Show

Low-carb diets produced several positive changes in heart health markers. Triglycerides (a type of blood fat linked to heart disease) dropped by about 15 mg/dL, which is meaningful. Blood pressure decreased modestly—systolic pressure (the top number) fell by about 2 mmHg and diastolic pressure (the bottom number) fell by about 1 mmHg. Good cholesterol (HDL) increased by about 3 mg/dL. Importantly, markers of inflammation in the body decreased, which is good for long-term heart health. Everyone in the studies lost weight and body fat, with the amount varying based on the type of diet and how long they followed it.

However, there was a trade-off: bad cholesterol (LDL) and total cholesterol increased slightly—by about 5 mg/dL and 4 mg/dL respectively. This increase was modest but worth monitoring. The researchers found that very strict ketogenic diets caused more LDL increase than moderate low-carb diets, suggesting that less extreme versions might be safer for cholesterol.

The benefits weren’t the same for everyone. Women saw more improvements than men. People who were overweight or had obesity saw bigger benefits. People with diabetes also benefited, though the effects varied. Diets that replaced carbs with both fat and protein together worked better than diets replacing carbs with just one or the other.

The length of time people stayed on the diet mattered. Longer interventions (studies lasting several months) showed bigger improvements in cholesterol ratios and inflammation markers compared to shorter studies. This suggests that the benefits build up over time. The way the diet was delivered also affected results—people who got more support and monitoring sometimes had better outcomes. Interestingly, the total number of calories people ate didn’t seem to change the basic benefits of low-carb diets, though it did affect weight loss amounts

These findings align with what many previous studies have shown about low-carb diets improving triglycerides and blood pressure. However, this massive analysis confirms that the LDL cholesterol increase is real and consistent, which some earlier studies had downplayed. The finding that moderate low-carb diets offer better balance than very strict ketogenic diets is newer and important. Previous research sometimes focused on extreme versions of low-carb eating, but this analysis shows that less extreme approaches might be safer while still providing benefits

The studies included varied widely in how long they lasted (some just weeks, others months or years), which makes it harder to compare. Some studies were better quality than others. The analysis couldn’t fully account for differences in how strictly people followed their diets—some people may have cheated more than others. Most studies lasted less than a year, so we don’t know about long-term effects beyond that. The studies also included mostly people from developed countries, so results might not apply equally to everyone worldwide. Finally, the studies measured different things in different ways, which required the researchers to convert everything to a common scale, potentially losing some detail

The Bottom Line

If you’re interested in a low-carb diet for weight loss or heart health, moderate low-carb approaches (not extreme ketogenic diets) appear to offer the best balance of benefits and safety. The evidence is fairly strong (high confidence) that you’ll lose weight and improve triglycerides and blood pressure. There’s moderate confidence that you’ll see improvements in inflammation and good cholesterol. However, there’s also moderate confidence that your LDL cholesterol will increase slightly. Before starting, get a baseline cholesterol test from your doctor. Aim to replace carbs with a mix of healthy fats (like olive oil, nuts, fish) and protein (like lean meat, eggs, beans) rather than just one or the other. Plan to stick with it for at least several months to see the full benefits. Get your cholesterol rechecked after 3 months and then regularly

This research is most relevant for adults who are overweight or have obesity and want to lose weight. Women may see more benefits than men. People with high triglycerides or high blood pressure should find this especially interesting. People with diabetes may benefit, though they should work closely with their doctor. People with very high LDL cholesterol or a family history of heart disease should be cautious and monitor closely. This research is less relevant for people at healthy weights who don’t have heart disease risk factors. Pregnant or breastfeeding women should consult their doctor before making major diet changes

You might notice weight loss within 2-4 weeks, though the first week is often just water weight. Blood pressure improvements typically appear within 4-8 weeks. Triglyceride improvements usually show up in blood tests after 4-12 weeks. The full benefits for inflammation markers and cholesterol ratios may take 3-6 months to fully develop. However, individual results vary significantly—some people see changes faster, others slower

Want to Apply This Research?

  • Track daily carbohydrate intake (aim for 45% or less of total calories) and weight weekly. Also log energy levels and any digestive changes. Set a reminder for monthly blood pressure checks at home if you have a monitor
  • Start by identifying your highest-carb foods and gradually replace them with protein and healthy fat options. For example, swap half your pasta for vegetables and add grilled chicken, or replace bread with eggs and avocado at breakfast. Use the app to log meals and see your carb percentage in real time, adjusting gradually rather than making drastic changes all at once
  • Use the app to track weight trends over 8-12 weeks rather than daily fluctuations. Set quarterly reminders to get blood work done (cholesterol panel, triglycerides, blood pressure). Log how you feel—energy, hunger, mood—to catch any negative effects early. Create a trend report every 3 months to share with your doctor and adjust your approach if needed

This research summary is for educational purposes only and should not replace professional medical advice. Low-carb diets may not be appropriate for everyone, especially people with certain medical conditions, those taking specific medications, pregnant or breastfeeding women, or people with a history of eating disorders. Before starting any new diet, particularly if you have heart disease, diabetes, high cholesterol, or take medications, consult with your doctor or registered dietitian. This is especially important because this research shows LDL cholesterol may increase on low-carb diets. Your doctor can monitor your individual response and adjust recommendations based on your specific health situation. The findings presented here represent general trends across many studies and may not apply to your individual circumstances.