Weight Loss Isn't the Only Thing That Matters for Heart Health

Losing weight seems simple on its face: eat fewer calories than you burn. But a new study from Washington University and the Center for Human Nutrition in St. Louis, Missouri, examined how different diets affect markers of heart health in people with “metabolically unhealthy” obesity.^[1] This randomized clinical trial followed 42 patients who were obese with prediabetes and hepatic steatosis (fatty liver disease).^[1] Researchers randomly assigned patients to receive one of three diets with different macronutrient profiles:^[1]

• Mediterranean
  • 15% protein
  • 35% fat
  • 50% carbs
• Very-low-fat plant-forward
  • 15% protein
  • 15% fat
  • 70% carbs
• Very-low-carb ketogenic
  • 23% protein
  • 75% fat
  • 4% carbs

Researchers provided all meals until the participants reached a moderate 10% weight loss.^[1] This approach helped isolate the impact of the diets from the effects of weight loss itself, helping determine if one of the diets was better for heart health.

The results were clear. Weight loss improved every measure of cardiovascular risk that was measured, including cholesterol and insulin sensitivity.^[1] Interestingly, the very-low-carb ketogenic diet had a much bigger effect on many cardiovascular factors than the other two diets, specifically:^[1] 

• Liver triglycerides, an indicator of liver disease, were lower
• HDL cholesterol, often called “good cholesterol,” stayed high, while it dropped in other diets
• Insulin, which is needed to digest sugars, had a lower base level, but still responded to sugar intake
• HbA1C, a measure of average blood sugar over time, dropped significantly

Together, this shows that a very-low-carb ketogenic diet improves markers related to liver health, prediabetes, and heart health more than other diets.^[1] Further, the scientists found improvements in GFR, a marker of kidney health.^[1] This is exciting, because it shows that diets aren’t all created equal, and that the type of diet can have big effects on health separate from the weight loss.^[1] Further, this gives an interesting counterpoint to a lot of traditional heart health advice: the very-low-carb ketogenic diet was extremely high in fat, including saturated fats, which are typically associated with poor heart health.^[1]  In the context of this study, however, saturated fat content does not appear to have negative effects when losing weight.^[1]

How does a ketogenic diet achieve these results? Normally, the body runs on glucose (blood sugar), which is stored as glycogen.^[1] This is a quick, on-demand energy source, but we only store a limited amount. When we run out of glycogen, the body may enter ketosis and start breaking down fat to use as energy.^[2] It generally takes around 2 weeks on a very-low-carbohydrate ketogenic diet to enter a ketogenic state.^[2] When this happens, insulin levels decrease, and glucagon levels increase.^[1] As a result, the body begins using stored fat for energy, and the liver produces ketones as an alternative fuel source.^[1] This study found that this ketogenic state has benefits for heart health beyond the normal benefits of weight loss.^[1]

So is a very-low-carb ketogenic diet the perfect diet? Very much no!^[2] To start, this study was small, with only 42 participants, and only lasted around 5-6 months.^[1] Further, the participants all had a set of specific conditions, obesity with prediabetes and hepatic steatosis, and it is unclear if these results would translate to other people.^[1] Also, it’s unknown if the cardiovascular benefits would remain in people on a very-low-carb ketogenic diet without weight loss.^[1] Studies have also found that ketogenic diets tend to have the greatest weight loss (and possibly cardiovascular benefit) in the first six months, and these differences often diminish within 2 years, when compared with other diets.^[2]

It is important to understand that a ketogenic diet can be dangerous.^[2] One possible outcome of unsupervised ketogenesis is a dangerous and potentially life-threatening condition called ketoacidosis, where uncontrolled ketosis can change the pH of the blood. This is particularly dangerous for patients on SGLT2 inhibitors; medicines that end in -gliflozin like Farxiga (dapagliflozin) and Jardiance (empagliflozin).^[2] Patients with pancreatitis should also avoid ketogenic diets because the high fat content may worsen their symptoms .^[2] People considering a ketogenic diet should talk to a doctor, and possibly a behavioral support team before large dietary changes such as adopting a very-low-carb ketogenic diet.^[2] Doctor support is particularly important for patients with:^[2] 

• Atherosclerotic cardiovascular disease (ASCVD)
• Heart failure
• Type 2 diabetes
• Kidney disease
• Liver disease

The long and short of it is that calories are not all equal. The type of diet we follow can have big effects beyond just how many calories we eat. This study is a new and interesting way to look at how the foods we eat affect our health, not just how much weight we may lose.

Creative Director Benton Lowey-Ball, MWC, BS, BFA

References:

[1] Petersen MC, Smith GI, Farabi SS, Palacios HH, Shankaran M, Hellerstein MK, Patterson BW, Klein S. Effect of diet macronutrient content on the cardiometabolic response to weight loss: A randomized clinical trial. Cell Metabolism. 2026 Aug 27; https://doi.org/10.1016/j.cmet.2026.07.020

[2] Kirkpatrick CF, Bolick JP, Kris-Etherton PM, Sikand G, Aspry KE, Soffer DE, Willard KE, Maki KC. Review of current evidence and clinical recommendations on the effects of low-carbohydrate and very-low-carbohydrate (including ketogenic) diets for the management of body weight and other cardiometabolic risk factors: a scientific statement from the National Lipid Association Nutrition and Lifestyle Task Force. Journal of clinical lipidology. 2019 Sep 1;13(5):689-711. https://doi.org/10.1016/j.jacl.2019.08.003