They become just as fat as normal mice, increasing their fat mass by nearly 150% in 16 weeks. There was no difference whatsoever in body weight or body fat gains between groups. I find it interesting that there's so much attention paid to the Cell Metabolism paper while this study, which is more relevant to common obesity, and published in the highest-impact journal in the world, apparently didn't make the cut.
This study, among many others, suggests that obesity and insulin resistance are related as such:
- Excess energy intake and/or fat gain leads to
- Inflammation, leading to
- Insulin resistance, resulting in
- Elevated insulin
Still think insulin causes obesity? Ask this guy what he thinks about it:
This is a photo from a paper titled "Insulin-sensitive Obesity" (2). According to the paper, that gentleman has a low insulin level similar to a lean person, and normal insulin sensitivity, despite having a body mass index of 45.2! This is true of a significant fraction of obese people, and it has been replicated in other studies (3). What differentiates insulin-sensitive from insulin-resistant obese people? Inflammation (2). Imagine that!