A recent clinical trial shows that a ketogenic diet may offer greater metabolic and liver health benefits for people with obesity than the Mediterranean diet or low-fat, plant-forward eating plans. Researchers compared the three diets in 42 people with obesity, prediabetes, and fatty liver disease, and found that while all three led to weight loss, the keto diet produced the most dramatic improvements in liver function and blood sugar control.

What Makes Keto Stand Out for Metabolic Health?

The study, published in Cell Metabolism on August 27, 2026, tracked participants over four to five months as they lost approximately 10% of their body weight. Each person received all their meals from the research team and met weekly with a dietitian to ensure they stuck to their assigned eating plan. The keto diet in the study provided just 4% of calories from carbohydrates and 73% from fat, compared with 50% carbohydrates and 35% fat for the Mediterranean diet, and 70% carbohydrates and 15% fat for the plant-forward approach.

The results were striking. In the keto group, liver fat decreased by an average of 67%, compared with 45% in both the Mediterranean and plant-forward groups. Even more impressive, around 50% of keto diet participants no longer met the criteria for prediabetes by the end of the study, compared with 29% in the Mediterranean group and just 7% in the plant-forward group.

One of the most surprising findings was that despite consuming the most fat, the keto group did not experience increases in blood cholesterol or triglycerides. This challenged a common concern about high-fat diets.

"The most surprising finding was that participants in the ketogenic diet group didn't experience an increase in blood fat or cholesterol levels despite consuming the most fat," said Max Petersen, MD, assistant professor in medicine and the study's first author at Washington University School of Medicine.

Max Petersen, MD, Assistant Professor in Medicine at Washington University School of Medicine

The research team discovered that the keto diet triggered specific metabolic changes that favored fat loss. The keto group showed the largest increase in glucagon, a hormone that promotes fat loss in the liver, and the greatest reduction in blood insulin levels, which helps reduce liver fat accumulation.

How Do These Three Diets Actually Differ?

Understanding the structural differences between these eating approaches helps explain why the keto diet showed superior results for liver and metabolic markers in this particular study. Each diet emphasizes different macronutrient ratios and food sources.

• Ketogenic Diet: A high-fat, very low-carbohydrate approach designed to shift your body into ketosis, where it burns fat for energy instead of carbohydrates. Typical macronutrient distribution includes 50-60% fat, 30-35% protein, and 5-10% carbohydrates.
• Mediterranean Diet: Based on traditional eating patterns from countries bordering the Mediterranean Sea, emphasizing fruits, vegetables, whole grains, nuts, legumes, and olive oil. It is higher in carbohydrates and lower in fat than keto, and focuses on minimally processed foods rather than ultra-processed options.
• Plant-Forward Diet: Centers on plant-based foods like fruits, vegetables, whole grains, and legumes, though it does not eliminate animal products entirely. Meat is included but is not the main feature of meals, making it the highest-carbohydrate option of the three.

All three diets successfully reduced body fat and improved insulin sensitivity, meaning participants' bodies became better at regulating blood sugar. However, the keto diet's specific macronutrient composition appeared to trigger more aggressive improvements in liver function and prediabetes reversal.

Important Caveats and Long-Term Sustainability

While the findings are encouraging, experts emphasize that the study had limitations that matter for real-world application. The trial included only 42 participants with specific characteristics, lasted about five months, and cannot easily be generalized to the broader population. Additionally, all three diets produced identical benefits for muscle preservation, suggesting that weight loss itself, rather than diet composition alone, remains the primary driver of metabolic improvement.

"The study was small but well-designed and controlled, delivering a clear message: when weight loss is equal, dietary composition still affects the liver. However, the benefit to muscle, which is the body's biggest sugar-burning engine, was identical across all three diets and resulted from weight loss. This means that the real star in metabolic health continues to be weight loss," explained Yesika Garcia, MD, board-certified endocrinologist with Medical Offices of Manhattan.

Yesika Garcia, MD, Board-Certified Endocrinologist at Medical Offices of Manhattan

Another critical consideration is sustainability. The keto diet is notoriously difficult to maintain over the long term, and diets only work if you actually follow them. The Mediterranean diet, by contrast, has what experts call the "deepest, most battle-tested track record" for preventing diabetes and heart disease over decades of research. It is also more sustainable because it functions as a lifestyle approach rather than a restrictive diet plan.

For people considering keto specifically for metabolic benefits, Dr. Garcia offered practical guidance: "For the right person with their doctor in their corner, keto might add a genuine metabolic boost. But mind the food quality, and above all, pick something you can actually stick with that fits your life." The bottom line is that the diet you can sustain consistently will always outperform the "perfect" diet you abandon after a few weeks.

Dr. Garcia

What About Weight Loss With GLP-1 Medications Like Zepbound?

For people using weight-loss medications like Zepbound (tirzepatide), a separate but related concern emerges: loose skin. While Zepbound itself does not cause loose skin, the rapid weight loss it enables can lead to excess skin if collagen and elastin fibers do not have time to retract. Clinical trials showed that Zepbound users achieved an average weight loss of 15 to 20% of body weight over 72 weeks while preserving lean muscle mass better than other weight-loss methods.

The medication primarily targets fat mass, including both subcutaneous fat (under the skin) and visceral fat (around organs), which is beneficial for metabolic health but can contribute to loose skin if fat loss happens too quickly. However, Zepbound's ability to preserve muscle mass provides some structural support that can help maintain skin tightness.

How to Prevent Loose Skin During Rapid Weight Loss

If you are losing weight quickly through medication or diet, several evidence-based strategies can help minimize loose skin and support skin elasticity during your weight-loss journey.

• Gradual Weight Loss: Aim to lose 1 to 2 pounds per week rather than losing weight as quickly as possible. Slower weight loss gives your skin time to adapt and allows collagen and elastin fibers to reorganize and retract, reducing the likelihood of sagging skin. This pace also helps preserve muscle mass and reduces the risk of nutrient deficiencies that can weaken skin structure.
• Resistance Training: Building muscle through strength training can visually fill out loose skin by increasing volume beneath the skin's surface. Resistance training stimulates collagen production, increases skin thickness, and reduces inflammatory factors that break down skin. Effective options include compound movements like squats and deadlifts, isolation exercises like bicep curls, and bodyweight exercises like push-ups and planks.
• Prioritize Protein Intake: Protein is the building block of collagen and elastin, so aim for 1 to 1.5 grams of protein per kilogram of body weight daily. Quality sources include lean animal proteins like chicken and white fish, dairy products like Greek yogurt and cottage cheese, plant-based proteins like lentils and chickpeas, and protein isolates when solid foods feel unappealing.
• Eat Skin-Supporting Foods: Certain foods provide nutrients that support skin health and elasticity, including fatty fish, berries, avocado, leafy greens, and bone broth. These foods contain vitamins, minerals, and compounds that support collagen and elastin function.
• Stay Well Hydrated: Proper hydration supports skin health by increasing moisture retention, helping skin "bounce back," aiding nutrient transport to skin cells, and reducing skin inflammation. Drinking plenty of water throughout your weight-loss journey supports both weight loss and skin elasticity.

The key takeaway across both the keto diet study and the Zepbound guidance is that sustainable, intentional weight loss with attention to diet quality, muscle preservation, and skin health produces the best long-term results. Whether you choose keto, Mediterranean, plant-forward, or medication-assisted weight loss, working with a healthcare provider to set realistic goals and monitor your progress remains essential.