Metabolism is the sum of everything your body does to stay alive: breathing, digesting, maintaining temperature, circulating blood. Most of that happens even when you are completely still. It is called basal metabolic rate, and it accounts for 60 to 75 percent of everything you burn in a day. The rest comes from voluntary movement and digestion. Understanding how GLP-1 affects this helps explain why weight loss is not always linear.
Metabolism is the sum of everything your body does to stay alive: breathing, digesting, maintaining temperature, circulating blood. Most of that happens even when you are completely still. It is calle...
What GLP-1 Does to Metabolism
GLP-1 receptor agonists have a direct effect on how the body uses energy. Studies show that semaglutide and tirzepatide increase resting energy expenditure in some people, especially in the first weeks of use. This means the body burns more just by existing, on top of what it would normally burn.
At the same time, reduced appetite makes you eat less. If the increase in expenditure does not offset the reduction in intake, you enter a caloric deficit and weight loss occurs. That is the basic mechanism. The problem is that the body is adaptive. When you lose weight, basal metabolism drops along with it, because a smaller body needs less energy to function. That is normal and happens with any weight loss method.
Registra tu peso y sincroniza pasos y entrenamientos con Apple Health.
Registrar en la appThe Effect of Lost Weight on Metabolism
When you lose 5 kilograms, your body needs less energy to carry that weight around. Muscles that are not being used as much can atrophy slightly if they are not stimulated. Fat that left the body took energy with it. The net result is that the body asks for less food than it did before, even if you do not feel hungrier. That is one reason weight loss slows down after the first few months.
GLP-1 does not stop this adaptive process, but it may blunt it. Some research suggests GLP-1 receptor agonists have independent thermogenic effects, meaning the body keeps burning more than the logic of weight loss alone would suggest. But this varies between individuals, and data are still being collected.
