Chronic hyperinsulinemia promotes metabolic dysfunction and fat accumulation, whereas acute insulin elevation supports anabolic processes such as muscle protein synthesis.

Study: Role of insulin in the regulation of human skeletal muscle protein synthesis and breakdown: a systematic review and meta-analysis

Short bursts of insulin help build muscle when you’ve eaten protein, but if insulin stays high all the time (like in type 2 diabetes), your muscles stop responding well and may even break down more — leading to worse metabolism and fat gain.

Study: Submucosal fat accumulation in human colorectal tissue and its association with abdominal obesity and insulin resistance

When people have consistently high insulin levels, their bodies store more fat in unusual places like the colon, and this study found that exact link in humans. Short-term insulin spikes (like after eating) aren't studied here, but the long-term high insulin → fat storage part is clearly supported.

Study: Association Between Fasting Insulin Levels and Handgrip Strength: A Cross-Sectional Study Using the Korean National Health and Nutrition Examination Survey

People with consistently high insulin levels had weaker hand strength, even if they weren’t overweight or diabetic — suggesting too much insulin over time hurts muscle health, while short bursts of insulin help build muscle.

Study: The role of insulin, corticosterone and other factors in the acute recovery of muscle protein synthesis on refeeding food-deprived rats.

When rats eat after fasting, their insulin spikes and helps their muscles quickly start building protein — but if you block insulin, this doesn’t happen. This shows short-term insulin boosts muscle growth, which matches the claim.