Incretins

Incretins are gut hormones released in response to food that help the body prepare for incoming nutrients. The main incretins are GLP-1 and GIP. They enhance glucose-dependent insulin secretion, influence glucagon, slow gastric emptying, contribute to satiety and connect the digestive system with the pancreas, liver and brain.

The point of the incretin response is that the body reacts to food before blood glucose changes dramatically. The same amount of glucose taken by mouth and given intravenously produces different insulin responses because the intestine adds its own hormonal signal. This helps distribute fuel after meals more precisely and explains why the stomach, intestine and meal composition matter for glycemia.

GLP-1 and GIP

GLP-1 is produced by intestinal L cells, especially in response to nutrients and signals from bile acids, the microbiota and the nervous system. It enhances insulin release only when glucose is elevated, reduces excessive glucagon, slows gastric emptying and supports satiety. This is why GLP-1 has become an important drug target in type 2 diabetes and obesity.

GIP is released by K cells in the upper small intestine and also strengthens the insulin response after meals. Its role is more complex because it is connected not only with glucose but also with fat metabolism. In insulin resistance and type 2 diabetes, the incretin effect can weaken: hormones are released, but tissues and the pancreas do not respond as effectively.

Food and the incretin response

Incretins are influenced not only by sugar, but also by protein, fat, fiber, gastric emptying speed and the order of foods in a meal. Protein stimulates insulin and some gut hormones, fat slows gastric emptying, and fiber fermentation can support satiety signals. Whole food usually produces a more manageable response than a sweet drink or soft ultra-processed food.

In reactive hypoglycemia, after gastric surgery or when food passes through the intestine very quickly, the incretin response may be excessive or poorly synchronized. Weakness, sweating, trembling, palpitations or sudden hunger can appear after meals. These symptoms should be distinguished from ordinary sugar cravings and assessed through glucose patterns, history and meal composition.

Keto, LCHF and glucose

Low-carbohydrate nutrition reduces the need for a large insulin response after meals because there is less starch and sugar. This can make glucose control easier in insulin resistance. But incretins do not disappear: protein, fat, meal volume, bile and intestinal signals continue to participate in satiety and metabolic regulation.

If a person on keto eats too little protein and vegetables, drinks fatty coffee constantly or relies on rare huge meals, appetite regulation can become less stable. A workable low-carbohydrate diet should provide a clear meal structure: protein, a reasonable amount of fat, tolerated vegetables, salt, water and predictable satiety without constant nausea or evening overeating.

Incretin-based medications

GLP-1 receptor agonists and dual drugs that affect GLP-1 and GIP are used medically for type 2 diabetes and obesity when indicated. They can reduce appetite, body weight and glucose, but they are drug therapy, not nutritional supplements. They have contraindications, side effects, dosing rules and a need for medical monitoring.

With these medications it is especially important not to lose protein intake and muscle mass. Appetite reduction can be useful, but if a person eats too little protein, moves too little and loses weight quickly, part of the result may come from muscle. Nausea, constipation, gallbladder issues, dehydration risk and combination with glucose-lowering drugs also matter.

When to look deeper

Medical evaluation is needed with diabetes, repeated hypoglycemia, marked weakness after meals, unexplained weight loss, persistent nausea, vomiting, severe abdominal pain, a history of pancreatitis or obesity with significant complications. Incretins are an important part of metabolism, but they should not be used for self-diagnosis or self-directed therapy.

Practically, the incretin system reminds us that food is not only calories and carbohydrates. The body evaluates texture, volume, protein, fat, fiber, nutrient delivery speed and intestinal state. The more whole and predictable a meal is, the easier it is for hormonal signals to work without sharp swings in hunger, glucose and overeating.