Why is insulin sensitivity as important?

[Ivan091]

If you don’t have a diabetes, then when your body fat increases and with it, insulin sensitivity decreases, pancreas will just produce proportionally more insulin to keep your blood sugar in physiological range. So why elevated insulin level just doesn’t fully compensate lowered receptors sensitivity and you start gaining more and more fat, and less lean mass, feel more fatigued and eventually experience insulin resistance symptoms?

[TolerantLactose]

lowered receptors

You're thinking that this is a global phenomenon. It's not. Your muscles become less insulin sensitive while your fat stays relatively the same. The pancreas does pump out more insulin and, in this environment, your fat cells become more active in nutrient uptake.

[Ivan091]

Thank you bro, but then - why do insulin resistant people experience symptoms like skin tags, brain fog, impaired vision and increased fatigue if its not global?

[TolerantLactose]

Global wasn't the right word. I should say uniform. Your lean tissue can become more insulin resistance while your fat stays the same. If you simply raise insulin to get the baseline response in muscle, your fat storage goes into overdrive.

[Heisman2]

The skin is a good example of what TolerantLactose said. Many people with insulin resistance but not diabetes will still have acanthosis nigricans and skin tags, and this is because insulin being anabolic drives increased growth of skin cells since the skin does not develop insulin resistance to the same degree as other organs.

That's an oversimplification but shows the general idea.

[Ivan091]

Okey, so actually when other tissues has remained normal sensitivity, it means that muscles can be casusally underfueled while some (for ex. skin) gets excess of nutrients? Then insulin resistance should cause not only gains in fat mass but also slow muscle growth?

[Heisman2]

Okey, so actually when other tissues has remained normal sensitivity, it means that muscles can be casusally underfueled while some (for ex. skin) gets excess of nutrients? Then insulin resistance should cause not only gains in fat mass but also slow muscle growth?

Quite possibly, though I have not seen any studies directly evaluating this. But as skeletal muscle is the primary tissue to uptake blood glucose and a consequence of insulin resistance is elevated blood glucose levels, this implies insulin is not functioning fully on skeletal muscle. Insulin is considered anabolic so this may inhibit hypertrophy as well. This is one reason I don't think it's a great idea to bulk at high levels of body fat, I prefer the notion of cutting to a reasonable body fat percentage first.