Hormones · metabolism · training
Why does the same surplus build muscle on one lifter and fat on another? Why do hips and thighs give up their fat last? The answers sit in your hormones: insulin sensitivity, cortisol, estrogen. These guides show you how they work, and exactly how to use them.
Each guide gives you the science in full, with the studies behind every claim. Then every section sums it up In Plain English: what it means for you, and one thing to do.
Same rigor, two readers. Every lifter starts with Muscle, Not Fat. Women who want answers made for their body add Built Different.
For men and women who lift
How natural lifters use insulin sensitivity to build a leaner physique.
Written for women
Your hormones, your shape: stubborn fat, glutes and cravings, explained.
Complete on its own. Read it alongside Muscle, Not Fat and you get the full picture: insulin and muscle on one side, your cycle, your fat distribution and your appetite on the other.
Every claim traces back to a published study: clamp studies, randomized trials, meta-analyses. Each one is listed at the end of the guide with a link to the paper.
You learn why a habit works, what insulin, cortisol or estrogen is actually doing, so you can adapt the plan to your life instead of following it blindly.
Every section ends with an “In Plain English” summary and a one-line “Do this”. Each guide closes with hour-by-hour templates and an 8-week plan.
A real page from Muscle, Not Fat
The Science
Where the two pathways meet. Both routes converge on AS160 and its sister protein TBC1D1. This convergence explains one of the most powerful facts in this guide: insulin and exercise do not just add up, they multiply. In a study of healthy volunteers, an insulin clamp alone produced glucose uptake of about 8.7 mg/kg/min, and light cycling alone about 1.4. Combined, uptake reached about 15.1 mg/kg/min, far more than the sum.3
Reference 3. DeFronzo RA et al. Synergistic interaction between exercise and insulin on peripheral glucose uptake. J Clin Invest 1981. Read the paper
Each guide has dozens of these: the science, a figure when the numbers matter, a plain-English summary, and one action.
About Endo & Iron
These guides grew out of the research reading behind a master’s degree in endocrinology and metabolism, in France. Every claim is checked against published, peer-reviewed studies, and every study is listed with a link to the original paper or its official abstract.
Endo & Iron publishes evidence-based guides on hormones, metabolism and training. No before-and-after photos, no miracle protocols: the research, explained clearly, and turned into a plan you can follow.
A PDF guide you can read on your phone, tablet or computer, with every study in the reference list as a clickable link. The download link arrives right after payment, on the confirmation page and by email.
Every lifter, man or woman, can start with Muscle, Not Fat. If you are a woman and want answers about your cycle, stubborn fat or cravings, Built Different covers them, and works on its own.
No. Everything relies on training, nutrition, sleep and supplements with real evidence behind them.
No. The guides are educational. If you have a medical condition, are pregnant or take medication, talk to your doctor before changing your diet, training or supplements.
Yes. If a guide isn’t what you expected, email us within 14 days of your purchase and we will refund you in full. See the refund policy.
Write to contact@endoandiron.com. Every message gets a reply.