Low-carb and low-fat diets each help some heart markers and worsen others, and no single approach wins across the board. A network meta-analysis in the European Journal of Nutrition compared carbohydrate-focused and fat-focused eating patterns in people at elevated cardiovascular risk, mapping out exactly where each pattern helps and where it hurts.
Why the comparison matters. The low-carb versus low-fat debate has run for decades, often framed as if one must be the universal winner. But cardiometabolic health is not a single number; it includes cholesterol fractions, triglycerides, body weight, blood pressure, and blood sugar, and a diet can improve one while nudging another in the wrong direction. This analysis was built to quantify those trade-offs rather than crown a champion.
What the study did. Researchers systematically searched trials published between January 2013 and October 2025 and pooled 47 randomized clinical trials with 3,450 adults aged 35 to 75, each with at least one cardiovascular risk factor. Diets were classified by their fat and carbohydrate distribution, with monounsaturated fat content treated as a marker of dietary quality, and a low-fat, moderate-carbohydrate diet used as the reference point. A random-effects network meta-analysis then estimated how each pattern shifted cardiovascular markers relative to that reference.
Body weight. High-fat, low-carbohydrate diets produced a modest reduction in body mass index, about -0.48 kg/m2 compared with the low-fat, moderate-carbohydrate reference. It is a real but small effect, not a dramatic advantage.
Cholesterol and triglycerides, where the trade-offs sharpen. Ketogenic diets showed the largest increases in LDL ("bad") cholesterol (+0.43 mmol/L) and total cholesterol (+0.55 mmol/L) versus the reference, but also the largest rise in HDL ("good") cholesterol (+0.12 mmol/L). High-carbohydrate diets moved a different lever, tending to raise triglycerides (+0.24 mmol/L). In short, carbohydrate restriction improved triglycerides and HDL but was not consistently favorable for LDL, the marker most tied to long-term heart risk.
What barely moved. Across the board, macronutrient composition had limited effects on waist circumference, blood pressure, and blood sugar markers, suggesting that the carb-versus-fat ratio is not the dominant lever for those particular measures.
The core message: trade-offs, not a winner. The authors concluded that no single macronutrient distribution is universally optimal. Distinct patterns buy improvements in some markers at the cost of others, so the "best" split depends on which risk factors an individual most needs to address.
How to read this. These trials defined diets mainly by broad macronutrient targets rather than by food quality, and the study measured short-to-medium-term changes in risk markers, not hard outcomes like heart attacks or deaths. That is a meaningful limitation: two low-carb diets, one built on fish, nuts, and olive oil and another on processed meat, are not nutritionally equivalent even if their macros match. The authors explicitly flag macronutrient quality and food-based patterns as what ultimately matters.
Practical takeaway. Rather than picking a camp, the results support matching the approach to the person: someone with high triglycerides and low HDL may benefit from moderating carbohydrates, while someone with high LDL may need caution with very high-fat or ketogenic patterns. In every case, the quality of the foods, minimally processed, rich in unsaturated fats and fiber, carries more weight than the ratio alone.
Bottom line. Whether to lean lower-carb or lower-fat depends on your own metabolic profile and which markers need the most attention, and the study's central lesson is that food quality, not just the balance of carbs to fat, is what counts most.