Keto Diet Shows Greater Liver Fat and Prediabetes Gains in a Small Trial
A controlled diet trial found larger liver fat reductions and more prediabetes reversals with keto, while raising questions for cyclists’ training fuel.
A tightly controlled diet trial found that adults with obesity, prediabetes and fatty liver disease had larger average reductions in liver fat on a ketogenic diet than on Mediterranean or plant-forward low-fat plans. The result points to a possible metabolic benefit from carbohydrate restriction beyond weight loss, though it doesn’t settle which eating pattern best fits an individual cyclist or their training.
Three diets, matched weight loss
Researchers at Washington University School of Medicine enrolled 42 adults with obesity, prediabetes and fatty liver disease. Participants followed one of three diets, with meals supplied by the research team:
- Ketogenic: 4% of calories from carbohydrates and 73% from fat.
- Mediterranean: 50% of calories from carbohydrates and 35% from fat.
- Plant-forward, very low fat: 70% of calories from carbohydrates and 15% from fat.
The researchers adjusted calorie intake so that participants in all three groups lost roughly 10% of their body weight over 4–5 months. Dietitians met with participants weekly to help them follow their assigned plan. By aiming for similar weight loss across groups, the study could compare outcomes associated with diet composition while limiting the influence of differences in weight lost.
The menus varied considerably. Keto meals included egg salad, bacon and sausage omelettes, pulled pork, Italian chicken with spinach, pecan-encrusted tilapia and salmon with cauliflower mash. The Mediterranean menu featured oatmeal with almonds and blueberries, minestrone, quinoa with black beans and corn, chicken pesto pasta and vegetable flatbread. The low-fat plant-forward plan included fruit smoothies, red beans and rice, vegetable shepherd’s pie, sweet potato and black bean soup, and vegetable chili. The listed meals also included some fish and other animal products, so “plant-forward” describes the pattern rather than an entirely plant-based menu.
The clearest differences were in liver fat and blood sugar
All three groups lost body fat and improved overall insulin sensitivity. But the ketogenic group had the largest average reduction in liver fat: 67%, compared with 45% in both the Mediterranean and low-fat groups.
The share of participants who no longer met the study’s criteria for prediabetes also differed. That was 50% in the keto group, 29% in the Mediterranean group and 7% in the plant-forward low-fat group. These are results from a trial of 42 adults, so they describe the participants studied; they don’t establish how every person with prediabetes or fatty liver disease would respond.
The distinction matters because weight loss was similar across the groups. The results suggest that, for these participants, the balance of carbohydrates and fat may have shaped liver and blood sugar outcomes in addition to the effects of losing weight.
What the findings may mean for cyclists
Corresponding author Samuel Klein said: “We know weight loss can improve metabolic health in people who are obese. Our data suggest that if you have high liver fat content and prediabetes, reducing carbohydrate intake can have important therapeutic effects on metabolism beyond just weight loss alone.”
The article also quotes Petersen on how diet fits alongside weight-loss medication: “GLP-1-based medications have revolutionized the therapy of obesity. We now have a very effective pharmacotherapy for achieving significant weight loss. But in addition, our study shows that the specific composition of the diet can give you added benefits.”
For cyclists, the metabolic result is only one part of the decision. High-intensity riding draws heavily on glycogen, which the body makes from carbohydrates. A keto diet sharply limits carbohydrate intake, so replenishing glycogen can take longer. Riding with low glycogen may encourage greater fat use during endurance work, but that can come at the expense of top-end speed and power. The trial didn’t test cycling performance, so its health measures don’t show how any of the three diets would affect an individual’s training or racing.
Anyone considering a major dietary change to address prediabetes or fatty liver disease should discuss the choice with a qualified health professional. For an athlete, it also makes sense to consider training demands and fueling needs. A lower-carbohydrate approach may suit some goals or periods of training, while sessions that depend on hard efforts may call for a different fueling plan. The evidence here supports a specific comparison in a small group; it doesn’t establish a single diet as the right fit for every rider.
A result to follow, not a universal prescription
The study offers a useful signal: when participants lost roughly the same amount of weight, those on keto had larger average reductions in liver fat and a higher rate of prediabetes reversal. That makes carbohydrate intake a relevant part of the discussion for people with these metabolic concerns. For cyclists, the practical takeaway is to weigh that potential benefit against the demands of their riding and to make health and fueling decisions with appropriate support.
More cycling and health coverage: cycling and weight loss and weight-loss medications.
