A prediabetes diet is usually judged by the number on the scale, but a randomized trial published on 27 August 2026 in Cell Metabolism suggests the make-up of that diet also changes what appears on a blood test. A team at Washington University School of Medicine in St. Louis gave 42 adults who had obesity, prediabetes and fatty liver disease one of three eating plans — ketogenic, Mediterranean, or low-fat and plant-forward — and adjusted calories so that every group lost roughly 10% of body weight over four to five months. The weight loss was matched. The laboratory results were not. In this article you will learn which markers moved furthest, how to read the same values on your own report, and where the evidence still stops short.
What the prediabetes diet trial actually compared
All three diets are routinely recommended for weight loss, and until now it was unclear whether any of them offered a metabolic advantage beyond the weight lost. The three plans differed sharply in composition. The ketogenic arm took just 4% of calories from carbohydrate and 73% from fat. The Mediterranean arm took 50% from carbohydrate and 35% from fat. The low-fat, plant-forward arm took 70% from carbohydrate and 15% from fat.
Every meal was supplied by the research team, and participants met a dietitian weekly. That level of control is unusual and is what makes the comparison informative: because calories were set so that each group reached the same 10% weight loss, any difference between groups points to diet composition rather than to weight change. It is also the study’s main limitation. Forty-two people is a small sample, and food that arrives ready-made for five months is not how anyone eats in ordinary life.
The measurements that moved the most
Body fat fell in all three groups, and insulin sensitivity improved in all three. The gap opened up in the liver and in glucose regulation.
| Outcome after 4-5 months | Ketogenic | Mediterranean | Low-fat, plant-forward |
|---|---|---|---|
| Body weight lost | نحو 10% | نحو 10% | نحو 10% |
| Liver fat reduction | 67% on average | 45% on average | 45% on average |
| No longer met prediabetes criteria | About 50% of participants | 29% of participants | 7% of participants |
| Blood insulin over 24 hours | Largest fall | نتيجة متوسطة | Smallest fall |
| Blood cholesterol and fats | No increase despite the highest fat intake | No adverse change reported | No adverse change reported |
The second row of that table is the one that matters for anyone holding a lab report. Leaving the prediabetes range is not a subjective improvement — it is a threshold crossing, defined by numbers a laboratory prints. Half of the ketogenic group crossed back over it in under five months.
Why liver fat and blood sugar move together
The liver of a healthy adult holds very little fat. When fat accumulates there, the organ responds less well to insulin, so the pancreas secretes more of it, and the excess insulin in turn pushes the liver to store more fat. The loop is self-sustaining, which helps explain why the NIDDK lists obesity, metabolic syndrome and type 2 diabetes among the conditions that make fatty liver disease more likely.
In the trial, the ketogenic group showed the largest rise in glucagon, a hormone that pushes the liver to release stored fat, alongside the largest drop in circulating insulin. Both changes work in the same direction: less signal to store fat in the liver, more signal to clear it. That is a plausible mechanism rather than a proven one, and the authors present it as such.
Fatty liver is usually silent, which is why it is often found on routine blood work rather than through symptoms. If your results have raised the question, a clinician can order a fatty liver blood test. Another article on this site examines the prediabetes A1c grey zone.
Reading your own numbers after a prediabetes diet change
Three laboratory values define the prediabetes range, and they are the ones worth watching if you change how you eat. According to the CDC, an A1C below 5.7% is normal, 5.7% to 6.4% indicates prediabetes, and 6.5% or higher indicates diabetes. Mayo Clinic gives the fasting values: below 100 mg/dL is normal, 100 to 125 mg/dL is prediabetes, and 126 mg/dL or higher on two separate tests indicates diabetes. On a two-hour glucose tolerance test, 140 to 199 mg/dL falls in the prediabetes band.
Timing matters as much as the threshold. A1C reflects roughly the previous three months, so a diet started six weeks ago will only partly show up. Fasting glucose reacts far faster but swings from day to day, which is why a single value rarely settles anything. If you want the reference intervals side by side, it helps to review the normal fasting glucose ranges. To translate a percentage into an average glucose figure, many people consult جدول تحويل HbA1c.
Liver markers move on their own schedule. Your report may include a full liver panel, and doctors commonly track مستويات ALT because that enzyme rises when liver cells are under strain. To distinguish patterns of liver injury, some laboratories also calculate an AST/ALT ratio. Glucose usually appears on لوحة الأيض الشاملة, which is often ordered alongside the normal triglyceride levels.
One caution the trial does not remove: an A1C can be misleading. The CDC lists severe anaemia, kidney failure, liver disease, certain haemoglobin disorders, recent blood loss and pregnancy among the situations that distort the result. A number that does not fit the clinical picture should be repeated, not acted on alone.
أحدث التطورات العلمية
The Cell Metabolism trial lands in a field that has moved quickly over the past three years. Four findings help place it.
A 12-month randomized trial in Sweden, called NAFLDiet, followed 150 adults who had prediabetes or type 2 diabetes. What it found: both a low-carbohydrate diet rich in polyunsaturated fat and a low-fat healthy Nordic diet reduced liver fat compared with usual care, and neither beat the other on that measure. The Nordic diet went further, also improving body weight, long-term glucose control, liver enzymes, triglycerides and markers of inflammation. What this means for you: cutting carbohydrate is one route to a less fatty liver, not the only one — and in that trial the plant-rich option looked at least as good overall.
A German study known as PLIS, later checked against the large American Diabetes Prevention Program, asked what separates people whose numbers return to normal from people who lose the same weight without normalising. What it found: those who got their fasting glucose, two-hour glucose and A1C back into the normal range had a far lower chance of developing type 2 diabetes over the following two years — roughly three quarters lower. What set them apart was better insulin sensitivity and less visceral fat — the deep fat around the organs — rather than a pancreas making more insulin. What this means for you: two people can lose identical weight and end up in very different places biologically, and the blood test is what tells them apart.
A follow-up analysis of the Diabetes Prevention Program made the point more bluntly. What it found: among people who lost more than 7% of their body weight, those who also returned to normal glucose values had roughly two thirds less risk of developing type 2 diabetes over six years than those who hit the weight target alone. What this means for you: the weight target is a means, and the normalised laboratory value is the actual goal.
Finally, a community trial in Kerala, India randomly assigned more than 1,000 women who had raised fasting glucose to a structured 12-month lifestyle programme or to standard care. What it found: about 46% of the programme group returned to normal glucose tolerance, against about 6% of the comparison group, with improvements in fasting glucose, A1C, weight and waist measurement. What this means for you: this was achieved outside a research kitchen, with ordinary food, which is reassuring for anyone who cannot follow a fully supplied diet.
All four are worth reading with the same caveat. None of them tested a ketogenic diet in the way the new Cell Metabolism trial did, and none of them licenses a self-prescribed diet without medical input.
When to speak to a doctor
Speak to a clinician before you make a large change to how you eat if any of the following applies: you take insulin or a glucose-lowering medicine, since a sharp carbohydrate reduction can cause hypoglycaemia unless doses are reviewed; you have known kidney, liver or heart disease; you are pregnant or breastfeeding; you have a history of an eating disorder; or you take medicines whose dose depends on diet, such as warfarin.
Book a review promptly, rather than waiting for the next routine test, if you develop unusual thirst, frequent urination, unexplained weight loss, persistent fatigue, or if a repeat result has crossed into the diabetes range. A single abnormal value is a reason to look again, not a diagnosis.
مسرد المصطلحات
| شرط | تعريف |
|---|---|
| مقدمات السكري | A state in which blood sugar is above normal but below the threshold for diabetes. It is defined by laboratory values, not by symptoms. |
| الهيموغلوبين السكري (HbA1c) | The percentage of haemoglobin carrying attached sugar. It reflects average blood sugar over roughly the previous three months. |
| جلوكوز الصيام | Blood sugar measured after at least eight hours without food. It is the most common first-line test for prediabetes. |
| MASLD | Metabolic dysfunction-associated steatotic liver disease: excess fat stored in the liver, unrelated to heavy alcohol use. Formerly called NAFLD. |
| Insulin sensitivity | How readily the body’s tissues respond to insulin. Lower sensitivity means more insulin is needed for the same effect. |
| الجلوكاجون | A pancreatic hormone that acts roughly opposite to insulin. It prompts the liver to release stored sugar and to break down stored fat. |
| الدهون الحشوية | Fat stored deep in the abdomen around the organs, as opposed to fat under the skin. It is more closely tied to metabolic risk. |
| ALT | Alanine aminotransferase, a liver enzyme. Levels tend to rise when liver cells are inflamed or damaged. |
| تجربة عشوائية مضبوطة | A study in which participants are assigned to groups by chance, so that differences between groups are less likely to reflect who chose what. |
| Remission of prediabetes | A return of glucose values to the normal range after having been in the prediabetes band. Researchers increasingly treat it as a target in its own right. |
الأسئلة الشائعة
Does this trial mean a ketogenic diet is best for prediabetes?
No. It means that, in 42 closely supervised adults losing the same amount of weight, the ketogenic arm showed larger falls in liver fat and more frequent return to normal glucose values over four to five months. It was a small, short study with all food provided. Longer trials, including NAFLDiet, found that a plant-rich low-fat pattern performed at least as well on several measures. The best diet remains the one a person can sustain, chosen with their clinician.
How long before a diet change shows up in my blood test?
Fasting glucose can shift within days to weeks. A1C lags because it reflects roughly three months of average blood sugar, so a meaningful change usually needs eight to twelve weeks. Liver markers vary; liver fat itself fell substantially over four to five months in this trial, but that was measured by imaging, not by a routine blood panel.
Can prediabetes really go away?
Glucose values can return to the normal range, and researchers now describe this as remission of prediabetes. It is not the same as a guarantee. The published work suggests that people who reach normal values keep a markedly lower risk of type 2 diabetes for years afterwards, provided the underlying changes are maintained.
Is a high-fat diet safe for my cholesterol?
In this particular trial, the ketogenic group showed no rise in blood fats or cholesterol despite eating the most fat, which surprised the authors. That result came from a small, tightly controlled study in people who were actively losing weight, and it cannot be generalised. Anyone with a lipid disorder, a family history of early heart disease, or an existing cholesterol treatment should have their lipid panel checked before and after a major dietary change.
Do I need an imaging scan to know if I have fatty liver?
Liver fat is quantified by imaging, not by a standard blood test. Blood work, however, offers useful signals: liver enzymes, glucose, triglycerides and non-invasive scores calculated from routine values. A clinician decides whether imaging or a fibrosis assessment is warranted.
My A1C is 5.8%. Should I be worried?
It falls in the prediabetes band, which is a signal rather than an emergency. The usual next steps are confirming the value, looking at fasting glucose alongside it, and reviewing the modifiable factors. Many people in that band never progress to diabetes, particularly when the result prompts a change.
مصادر
- مراكز السيطرة على الأمراض والوقاية منها — فحص A1C للسكري ومقدماته، 2024 — cdc.gov
- National Institute of Diabetes and Digestive and Kidney Diseases (NIH) — Eating, Diet, and Nutrition for NAFLD and NASH, 2021 — niddk.nih.gov
- Mayo Clinic — Prediabetes: Diagnosis and Treatment, 2023 — mayoclinic.org
- 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 — doi.org/10.1016/j.cmet.2026.07.020
- Fridén M, Rosqvist F, Kullberg J, et al. — Effects of an anti-lipogenic low-carbohydrate high polyunsaturated fat diet or a healthy Nordic diet versus usual care on liver fat and cardiometabolic disorders in type 2 diabetes or prediabetes: a randomized controlled trial (NAFLDiet) — Nature Communications, 2025 — doi.org/10.1038/s41467-025-65613-2 (retrieved via PubMed)
- Sandforth A, et al. — Mechanisms of weight loss-induced remission in people with prediabetes: a post-hoc analysis of the randomised, controlled, multicentre Prediabetes Lifestyle Intervention Study (PLIS) — The Lancet Diabetes and Endocrinology, 2023 — consensus.app
- Jumpertz von Schwartzenberg R, et al. — Role of weight loss-induced prediabetes remission in the prevention of type 2 diabetes: time to improve diabetes prevention — Diabetologia, 2024 — consensus.app
- Mathews E, et al. — Effectiveness of lifestyle modification in prediabetes remission among women with isolated impaired fasting glucose: a community-based, randomised controlled trial in India — Diabetes Research and Clinical Practice, 2026 — consensus.app
للمزيد من القراءة
- Insulin resistance without obesity: what your blood tests reveal
- فحوصات الدم لمرض السكري: الجلوكوز، والهيموغلوبين السكري HbA1c، والأنسولين
- تحليل الدهون: الكوليسترول، LDL، HDL والدهون الثلاثية
- How to lower ALT levels: 8 steps to protect your liver
- ارتفاع الكوليسترول: الأعراض والأسباب والأرقام والعلاج
افهم نتائج مختبرك باستخدام AI DiagMe
A prediabetes report rarely comes with an explanation. Yet the values that decide whether you sit above or below the threshold — fasting glucose, A1C, liver enzymes, triglycerides — are printed on the same page, and they only make sense read together. AI DiagMe turns that page into plain language, marker by marker, so you arrive at your next appointment knowing which questions to ask. It helps you understand your results; it does not diagnose, and it does not replace your doctor.
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