Normally the liver and pancreas hold little fat, the liver is insulin-sensitive, and beta cells release a first-phase burst of insulin within minutes of a meal.Start with the normal state. The twin-cycle hypothesis places the start of type 2 diabetes in the fat inside two organs: the liver and the pancreas.
Liver:
· Liver cells hold only a little (liver fat above about 5% is usually counted as fatty liver) · Newly made fat (DNL) and the fat exported as VLDL are roughly in balance · Insulin-sensitive: when insulin rises after a meal, the liver releases less glucose into the blood
Pancreatic islets:
· There is little fat around the beta cells · When blood glucose rises after a meal, beta cells release a burst of insulin within minutes, called the first phase of secretion
Muscle and fat tissue:
· Insulin moves transporters to the cell membrane, which lets glucose into the cells
The point of the hypothesis: what matters is not only the number on the scale, but where the extra fat ends up.
2 · twin cycle ignites
A long energy surplus first stores fat in the liver; according to the hypothesis, extra fat in the blood then settles in the pancreas and weakens first-phase insulin secretion.The first cycle ignites in the liver. When energy intake exceeds use for a long time, part of the surplus is stored in the liver:
· Liver fat rises and becomes fatty liver (now called ) · The liver makes more new fat, and insulin holds back the liver's glucose output less and less · The liver sends more VLDL into the blood, so blood rise and runs low
The second cycle is in the pancreas. According to the hypothesis, the extra fat in the blood is also deposited in the pancreas:
· Beta cells sit in too many fatty acids for too long (lipotoxicity) and develop endoplasmic reticulum stress · The first phase of insulin secretion weakens · Once blood glucose is high, the high glucose itself damages beta cells further (glucotoxicity)
A personal fat threshold (also a hypothesis): people differ in how much fat they can store safely. Some develop fatty liver at a modest , while others have a higher BMI and still normal glucose. So waist size, liver enzymes () and triglycerides fill in what BMI alone cannot show.
3 · vicious loop
The two cycles reinforce each other: liver fat raises pancreatic fat, insulin secretion weakens, glucose rises, and chronically high insulin makes the liver build still more fat.The two cycles reinforce each other:
Liver fat rises → VLDL output rises → pancreatic fat rises and first-phase insulin secretion falls → blood glucose rises (after meals first, then fasting) → insulin stays chronically high, on top of insulin resistance. And the high insulin pushes the loop back round:
· The liver makes even more fat (high insulin drives SREBP-1c) · Muscle takes up less glucose · Fat tissue releases more free fatty acids, which return to the liver
How it usually unfolds in the clinic (gradually, over many years):
· Prediabetes ( 5.7–6.4% by the American Diabetes Association definition): glucose is still just about held down, but the beta cells are already straining · Type 2 diabetes (HbA1c ≥ 6.5%): usually glucose after meals rises first and fasting glucose follows · After many years of disease: more and more beta cells are lost, and remission becomes hard
The hypothesis explains why type 2 diabetes so often gets worse year by year: not necessarily because beta cells suddenly break, but because fat and high glucose keep holding them down, so they cannot work at their real capacity. Early in the disease this suppression can be lifted, and that is exactly what the DiRECT trial tested.
4 · DiRECT reversal
In a trial of adults diagnosed with type 2 diabetes within 6 years, months of formula diet replacement led to 46% remission at 12 months, versus 4% of controls.DiRECT (Lean 2018, The Lancet): 49 UK primary-care practices, 306 adults with type 2 diabetes diagnosed within 6 years, 27–45, not using insulin.
The program:
· At the start, glucose-lowering and blood-pressure drugs were stopped under a doctor's supervision · 3–5 months: 825–853 kcal a day of formula total diet replacement · Then solid food brought back gradually over 2–8 weeks · After that, long-term support for keeping the weight off
At 12 months: 46% of the intervention group were in remission ( still below 6.5% at least 2 months after stopping all glucose-lowering drugs), versus 4% of controls. Remission tracked weight loss: with both groups counted together, 86% of those who lost 15 kg or more were in remission.
At 2 years (Lean 2019): 36% were still in remission, versus 3% of controls.
A clue to the mechanism: in Lim 2011, a study of 11 people on a very-low-calorie diet for 8 weeks, liver fat fell first and fastest, pancreatic fat fell more slowly, and the beta cells' first-phase secretion recovered along the way. This is the most direct support for the twin-cycle hypothesis, but the sample is very small.
Points to read carefully:
· Stopping the drugs is a doctor's job: taking glucose-lowering drugs as usual while calories drop sharply risks low blood sugar · When the weight comes back, remission fades: keeping the weight off decides whether remission lasts · Remission is judged by HbA1c and medication, which are measures; the trial did not answer whether weight loss reduces heart attacks or strokes · For people with long-standing disease and heavy beta-cell loss, the chance of remission is much smaller, and the goal shifts to glucose control and fewer complications
This is not dieting at home on your own. It is a structured treatment with follow-up from doctors and dietitians.
Mechanism
DiRECT twin cycle · liver-pancreas fat overflow + reversal window