Insulin
The hormone that lowers blood glucose and directs nutrients into storage.
Insulin is the hormone released by the pancreas when nutrients arrive, chiefly carbohydrate but protein too. Its job is to move glucose out of the blood and into muscle, liver and fat, and to switch the body from breaking things down to storing and building.
It matters because that switch runs continuously, not just after meals. Insulin is what stops fat being released from storage while a meal is being processed, which is entirely normal and is not the same as making you fat. Body fat rises when energy intake exceeds expenditure, and insulin is the traffic control rather than the cause.
The condition worth understanding is insulin resistance: cells respond less readily, so the pancreas releases more to get the same effect. Blood glucose can look completely normal for years while that compensation holds, which is why fasting insulin and HbA1c can tell a different story from a single glucose reading.
Muscle is the main destination for glucose, and it takes some up during exercise through a route that does not need insulin at all. That is one reason a single training session improves glucose handling for a day or so, and why regular activity improves insulin sensitivity independently of weight loss.
Weight loss is the most powerful lever where there is weight to lose. In the DiRECT trial a primary care weight management programme put 46% of participants into remission from type 2 diabetes at one year, with remission tracking closely with the amount lost.
The everyday version of the advice needs no hormonal theory: keep training, keep muscle, keep the waist in check, sleep properly, and get glucose and HbA1c checked rather than inferred. Diets built around avoiding insulin spikes are solving a problem that healthy physiology does not have.
In practice, our metabolic fitness index reads these markers together, and the CGM metrics calculator interprets sensor data if you have it.
Sources
- Lean MEJ, et al. Primary care-led weight management for remission of type 2 diabetes (DiRECT): an open-label, cluster-randomised trial. Lancet 2018;391:541-551
- Matthews DR, et al. Homeostasis model assessment: insulin resistance and beta-cell function from fasting plasma glucose and insulin concentrations in man. Diabetologia 1985;28:412-419