Nutrition & Diet · RESEARCH EXPLAINED
If two diets lead to similar weight loss, does the composition of the diet still matter? A 2026 randomized trial compared that question under closely supervised conditions.
What researchers compared
Washington University researchers randomized 55 adults with obesity, prediabetes, and fatty liver to three diets; 42 completed the study, 14 per group. [1]
- Very-low-carbohydrate ketogenic: about 4% of energy from carbohydrate.
- Mediterranean: about 50% of energy from carbohydrate.
- Very-low-fat, plant-forward: about 70% of energy from carbohydrate.
Food was provided and participants received weekly dietitian support while losing approximately 10% of body weight. The menus differed in several nutrients, including protein and fat, so this was a comparison of dietary patterns rather than carbohydrate alone.
What they found
Muscle insulin sensitivity increased by about 50% in all groups, without a significant difference between diets. Liver fat fell by 67% in the ketogenic group versus 45% in each other group. The increase in the liver insulin-sensitivity index was two to three times greater with the ketogenic diet. [1]
At the end of the intervention, 50% of the ketogenic group no longer met the study’s prediabetes criteria, compared with 29% in the Mediterranean group and 7% in the very-low-fat group. These are results in small groups at one follow-up assessment, not proof of a lasting cure.
What the finding does not mean
The trial lasted months, not years. Participants had a specific combination of conditions, and receiving every meal and weekly support differs from everyday shopping and cooking. Thirteen randomized participants did not complete the study.
The findings do not establish that keto is the healthiest diet for everyone or that it prevents heart attacks or other long-term outcomes. LDL cholesterol and apolipoprotein B did not differ significantly between diet groups in this trial. Longer follow-up is needed to assess sustained benefits, adherence, and risks. [1]
The takeaway
Diet composition may affect particular metabolic outcomes beyond the amount of weight lost. That is more specific than declaring one diet the winner. For a major dietary change—especially with a medical condition or prescribed medication—work with a clinician or registered dietitian.
Sources & further reading
- Petersen et al. (2026). Effect of diet macronutrient content on the cardiometabolic response to weight loss: A randomized clinical trial. Cell Metabolism. DOI: 10.1016/j.cmet.2026.07.020. PubMed record.
Educational information for adults, not personalized medical, nutrition, or training advice. Prepared with AI assistance; qualified subject-matter review pending. Xtinction Nutrition sells supplements. Cited organizations and researchers do not endorse this publication or our products. These studies do not test the finished PWX-1 formula.
Nutrition & Diet · RESEARCH EXPLAINED
If two diets lead to similar weight loss, does the composition of the diet still matter? A 2026 randomized trial compared that question under closely supervised conditions.
What researchers compared
Washington University researchers randomized 55 adults with obesity, prediabetes, and fatty liver to three diets; 42 completed the study, 14 per group. [1]
- Very-low-carbohydrate ketogenic: about 4% of energy from carbohydrate.
- Mediterranean: about 50% of energy from carbohydrate.
- Very-low-fat, plant-forward: about 70% of energy from carbohydrate.
Food was provided and participants received weekly dietitian support while losing approximately 10% of body weight. The menus differed in several nutrients, including protein and fat, so this was a comparison of dietary patterns rather than carbohydrate alone.
What they found
Muscle insulin sensitivity increased by about 50% in all groups, without a significant difference between diets. Liver fat fell by 67% in the ketogenic group versus 45% in each other group. The increase in the liver insulin-sensitivity index was two to three times greater with the ketogenic diet. [1]
At the end of the intervention, 50% of the ketogenic group no longer met the study’s prediabetes criteria, compared with 29% in the Mediterranean group and 7% in the very-low-fat group. These are results in small groups at one follow-up assessment, not proof of a lasting cure.
What the finding does not mean
The trial lasted months, not years. Participants had a specific combination of conditions, and receiving every meal and weekly support differs from everyday shopping and cooking. Thirteen randomized participants did not complete the study.
The findings do not establish that keto is the healthiest diet for everyone or that it prevents heart attacks or other long-term outcomes. LDL cholesterol and apolipoprotein B did not differ significantly between diet groups in this trial. Longer follow-up is needed to assess sustained benefits, adherence, and risks. [1]
The takeaway
Diet composition may affect particular metabolic outcomes beyond the amount of weight lost. That is more specific than declaring one diet the winner. For a major dietary change—especially with a medical condition or prescribed medication—work with a clinician or registered dietitian.
Sources & further reading
- Petersen et al. (2026). Effect of diet macronutrient content on the cardiometabolic response to weight loss: A randomized clinical trial. Cell Metabolism. DOI: 10.1016/j.cmet.2026.07.020. PubMed record.
Educational information, not medical advice. These studies do not test the finished PWX-1 formula. Consult a qualified healthcare professional about individual health, dietary, or exercise needs.
