In adults with obesity, endurance exercise leads to a simultaneous decrease in two related proteins, IGF-1 and IGFBP-3, which may reflect a liver-controlled process that keeps a specific form of IGF-1 at stable levels, possibly to adjust to metabolic changes.

During short bouts of endurance exercise, people with obesity maintain the same levels of bioactive IGF-1 in their blood as lean individuals, even though overall IGF-1 and its binding protein increase less than in lean people.

When people with obesity do a single session of moderate-intensity cardio, their blood levels of IGF-1 and IGFBP-3 do not rise, unlike in lean individuals, suggesting the liver of people with obesity responds less to exercise in terms of producing these growth-related proteins.

Adults with obesity have a smaller increase in growth hormone after short bouts of endurance exercise than lean adults, and this may be linked to lower production of IGF-1 and IGFBP-3 by the liver.

In adults with obesity, changes in IGF-1 levels during endurance exercise are not related to the degree of insulin resistance, suggesting that insulin resistance does not directly control how IGF-1 responds to this type of physical activity.

When muscles are strongly activated during physical exercise, the body produces more insulin-like growth factor 1 (IGF-1), a protein involved in tissue growth and repair.